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Fast and Simple Evaluation of the Catalysis and Selectivity Induced by External Electric Fields
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  • Pau Besalú-Sala
    Pau Besalú-Sala
    Institut de Química Computacional i Catàlisi and Departament de Química, Universitat de Girona, Campus de Montilivi, 17003 Girona, Catalonia, Spain
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    Orcidhttps://orcid.org/0000-0002-0955-9762
  • Miquel Solà
    Miquel Solà
    Institut de Química Computacional i Catàlisi and Departament de Química, Universitat de Girona, Campus de Montilivi, 17003 Girona, Catalonia, Spain
    More by Miquel Solà
    Orcidhttps://orcid.org/0000-0002-1917-7450
  • Josep M. Luis*
    Josep M. Luis
    Institut de Química Computacional i Catàlisi and Departament de Química, Universitat de Girona, Campus de Montilivi, 17003 Girona, Catalonia, Spain
    *Email: [email protected]
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    Orcidhttps://orcid.org/0000-0002-2880-8680
  • Miquel Torrent-Sucarrat*
    Miquel Torrent-Sucarrat
    Department of Organic Chemistry I, Centro de Innovación en Química Avanzada (ORFEO-CINQA), Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU) and Donostia International Physics Center (DIPC), P Manuel Lardizabal 3, E-20018 Donostia/San Sebastián, Euskadi, Spain
    Ikerbasque, Basque Foundation for Science, Plaza Euskadi 5, 48009 Bilbao, Euskadi, Spain
    *Email: [email protected]
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    Orcidhttps://orcid.org/0000-0003-2689-0278
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ACS Catalysis

Cite this: ACS Catal. 2021, 11, 23, 14467–14479
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https://doi.org/10.1021/acscatal.1c04247
Published November 17, 2021

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Abstract

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In the oriented external electric-field-driven catalysis, the reaction rates and the selectivity of chemical reactions can be tuned at will. The activation barriers of chemical reactions within external electric fields of several strengths and directions can be computationally modeled. However, the calculation of all of the required field-dependent transition states and reactants is computationally demanding, especially for large systems. Herein, we present a method based on the Taylor expansion of the field-dependent energy of the reactants and transition states in terms of their field-free dipole moments and electrical (hyper)polarizabilities. This approach, called field-dependent energy barrier (FDBβ), allows systematic one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) representations of the activation energy barriers for any strength and direction of the external electric field. The calculation of the field-dependent FDBβ energy barriers has a computational cost several orders of magnitude lower than the explicit electric field optimizations, and the errors of the FDBβ barriers are within the range of only 1–2 kcal·mol–1. The achieved accuracy is sufficient for a fast-screening tool to study and predict potential electric-field-induced catalysis, regioselectivity, and stereoselectivity. As illustrative examples, four cycloadditions (1,3-dipolar and Diels–Alder) are studied.

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Introduction

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The interaction between molecules and external electric fields (EEFs) generates a broad range of effects. (1) Common observed phenomena are the changes in molecular geometry, vibrational structure, Stark effect, spin polarization, triggered electron transfer, chirality, and modification of absorption and emission properties. (2) Among them, the interest of the EEF effects on reactivity and selectivity is growing hugely since several practical applications of EEF-aided control on reactivity are being developed. (3) Since the field-induced change on regioselectivity in Diels–Alder (DA) reactions predicted by Shaik and co-workers (4) was experimentally validated, (3d) this chemistry is becoming more tangible and there has been a reborn of the topic also from the theoretical perspective. (5) Additionally, examples of the application of EEF on very diverse topics as the tuning of photo- and excited-state chemistry, (6) switch molecular diodes, (7) quantum tunneling, (8) and homo- and heterogeneous catalysis have been successfully investigated. (7,9)
One of the basic principles ruling the EEF potential applications is the control over the alignment between the molecule and the applied EEF. Currently, this new chemistry framework is investigated with the aid of very specific equipment as scanning tunneling microscopes, (10) and using laser-induced oscillating fields, (11) plasmonic modes in nanocavities, (12) and tribo- or piezoelectricity. (13) Therefore, improvements toward this direction are advancing by leaps and bounds.
The electric-field-induced chemistry can also be studied in the electrochemical double layer, (14) the interface layer between the electrode and the electrolyte. In this region, the molecular electron density of the reactants and their reactivity can be altered by the electric fields generated by the electrode. (15) The characterization of the electric field generated in the electrochemical double layer is a complex task, although the combination of the vibrational stark shift spectroscopy (16) and computational modeling is paving the way. (2a,17)
From another perspective, nature has been using electric fields to tailor its reactivity ubiquitously. Since the shape of the binding pockets of enzymes presents a well-defined structure of polar and charged amino acids, a local electric field (LEF) is generated in the active site of enzymes. (18) The LEFs can, thus, promote electrostatic-induced catalysis in enzymes. Several works have already been reported, mainly focused on heme and nonheme iron proteins, (19) illustrating the LEFs potential utility in the control of reactivity and, more interestingly, selectivity.
Head-Gordon and co-workers (5e,20) and Hammes-Schiffer and co-workers (21) have used a bond dipole and electric field theoretical model to project the field onto the relevant bonds that are broken and formed along the reaction pathway. The difference between native and modified protein scaffolds allows the suggestion of possible mutations that tune the LEF to improve the enzyme efficiency. (22) For instance, this computational directed evolution has allowed an artificial Kemp Eliminase with a 43-fold improvement in the reaction rate of the enzyme. (23)
The main challenge of the computational evaluation of EEF effects on reactivity is the high amount of computational time requested since the number of calculations grows arithmetically with the number of electric-field strengths and directions investigated. (24) In this regard, the development of new computational methods is required to predict the reactivity and selectivity induced by EEFs at a feasible computational cost even when large chemical systems are involved. In this work, we present a new methodology to efficiently screen the effect on the reactivity and selectivity of an EEF applied with any strength and direction that can be used as a fast semiquantitative tool for the modeling, designing, and understanding of EEF-aided chemistry.

Theory

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The in-depth study of the field-dependent energy barriers (FDB) for one specific reaction involves computation of the reactants and the corresponding transition states (TSs) within external electric fields of several different strengths and directions. Consequently, it requires a tedious task that involves huge quantities of central processing unit (CPU) time even for medium-sized molecular systems.
For a given chemical system, the exact energy in the presence of an electric field can be expressed as a Taylor expansion around free-field energy
(1)
where F is the external electric field strength vector and μ, α, β, and γ are the permanent dipole moment, the electrical polarizability matrix, and the first and second electrical hyperpolarizability tensors, respectively, defined as
(2)
where the indices i, j, k, and l indicate Cartesian axes x, y, or z. Using eq 2 to express the field-dependent energy of the reactants and TS, the field-dependent energy barrier (FDB) of a reaction, ΔE‡(F), is given by
(3a)
(3b)
where P = μ, α, β, and γ, and ETS(PTS) and ER(PR) are the electronic energies (molecular electrical properties) of the transition state and reactants, respectively.
For practical implementation of eq 3a, such expansion must be truncated. For instance, the truncation at the first term models the linear response of the barrier with respect to the EEF applied. Nevertheless, we can anticipate here that the neglect of the field-dependent nonlinear response of the barrier may lead to important quantitative or even qualitative errors in the predictions of the field-induced regioselectivity. Thus, the nonlinear terms are required to describe correctly the EEF effect on the energy barriers of chemical reactions. Conversely, the truncation of eq 3a at the third-order correction (given by β) yields an expression flexible enough to properly evaluate the perturbation of the energy barriers induced by EEFs of any strength and direction at a low computational cost.
(4)
Equation 4 is used throughout this work if not stated otherwise. It only requires the calculation of the field-free energy, μ, α, and β tensors for the reactants and transition states, which can be calculated analytically using several quantum chemistry packages. We refer to this approach to compute the FDB based on eq 4 as FDBβ. The benefits of including higher-order terms in eq 4 were also explored, but the changes in energy barrier due to the higher-order terms were usually below density functional theory (DFT) intrinsic errors. It is important to remark that the truncation at the linear term of eq 4 has been used in the literature to estimate the changes in the energy barriers induced by EEFs and light-emitting diodes (LEDs). (1c,5e,25)
The total electric polarizabilities and hyperpolarizabilities can be divided into the electronic contribution (Pel), the nuclear relaxation (nr) contribution (Pnr), and the curvature contribution (Pcurv). (26)
(5)
where Pel describes the response of the electrons to an external electric field at the equilibrium geometry, whereas Pnr and Pcurv arise from the change of the electronic and vibrational energies due to the field-induced change of the equilibrium geometry and the shape of the potential energy surface (PES), respectively. The nuclear relaxation contribution contains all of the harmonic and lowest-order anharmonic terms, whereas the curvature contribution includes the rest of the higher-order vibrational anharmonicity. Pcurv contribution is usually smaller than Pel and Pnr, and far more expensive to compute, and it has not been evaluated in this work. (27)
Finally, it is worth noting that the field-induced changes in the thermodynamics of the reactions can be also easily computed and represented from an approximation homologous to FDBβ, expanding in a Taylor series the field-dependent reaction energies (for more details, see Figure SI8).

Computational Details

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All electronic structure calculations have been performed using Gaussian16 software package. (28) For three studied cycloadditions, the geometries were optimized with the B3LYP exchange–correlation functional (29) using a 6-31+G(d,p) basis set (30) to span the atomic orbitals. Empirical dispersion corrections were added using the Grimme D3 correction (31) with Becke–Johnson damping factor. (32) Then, energy corrections, dipole moments, and (hyper)polarizabilities were obtained using the B3LYP functional and the 6-311+G(2d,2p) basis set, i.e., B3LYP-D3BJ/6-311+G(2d,2p)//B3LYP-D3BJ/6-31+G(d,p). For the Diels–Alder cycloaddition between maleic anhydride and cyclopentadiene and to facilitate the direct comparison with the study of Shaik et al., (4) the optimizations were performed using the BP86 functional, (33)i.e., the computational level used for this reaction was B3LYP/6-311++G(d,p)//BP86/6-31+G(d). All stationary points on the potential energy surface (PES) were characterized through analytical vibrational frequency calculations.
To validate our approach, we have also computed the effect of explicit external static electric fields on the energy barriers. Several field strengths (F) were considered in the range F = [−10–2,10–2] au (1 au = 51.4 V·Å–1) for all of the studied reactions; this range spans the order of magnitude of intrinsic LEF present in enzyme pockets or mitochondrial membrane interfaces. (34) It is important to remark that the positive direction of the electric field vector is defined from the negative to the positive charge, following the Gaussian16 convention (contrary to the conventional physics definition). (25) Notice that all of the calculations have been performed in the gas phase (for the solvent-phase electric field effect on a reaction, see the recent work of Dubey et al. (35)).
The field-free reactants were oriented by defining the z-axis as the reaction axis, i.e., the axis along which the bonds are formed or broken. To avoid undesired field-induced rotations of the chemical systems during the geometry optimizations in the presence of explicit electric field, an in-house code was set up. The field-dependent equilibrium geometry is considered aligned to the original field-free equilibrium geometry when the rotation between them is smaller than 0.1° for the x, y, and z-axes. It is worth noticing that these constraints were added to ensure the formation of a reactant complex would correspond to an experimental scenario where one reactant is immobilized, for example, by being absorbed on a surface. (4,9f) The activation energy barriers for any strength and direction of the EEFs using the FDBβ approach can be generated using an open-access script available at https://github.com/pau-besalu/FDB.
Preferably, the Pnr contribution should be computed at the same level of calculation as the electronic contribution. However, the energies and electronic contributions to the molecular electrical properties were computed using a triple-ζ basis (6-311++G(d,p) or 6-311+G(2d,2p)), while the equilibrium geometry and frequency calculations required to calculate the nuclear relaxation contribution were performed using a double-ζ basis (6-31+G(d,p)). Therefore, Pnr was computed using double-ζ basis, although we have checked that calculating Pnr with the triple-ζ basis leads to very similar results for the field-dependent energy barriers (for more details, see Table SI1).

Results and Discussion

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Initially, two 1,3-dipolar cycloadditions and one Diels–Alder (DA) cycloadditions involving small/medium-sized organic molecules are studied. For these first three reactions, the chemical barriers are computed using both FDBβ and through the explicit optimization of equilibrium geometries of reactant complexes and TSs under EEF of several strengths and directions. After that, taking advantage of the computational benefits of the FDBβ methodology, we have studied the DA cycloaddition between C60 fullerene and a diene. For this reaction, the determination of the geometries of reactant complexes and TSs under an electric field of several strengths and directions become computationally demanding. On the other hand, the FDBβ methodology only requires the evaluation of field-free dipole moments and (hyper)polarizabilities of the reactant complexes and TSs at their stationary points. Additionally, we introduce the two-dimensional (2D) representations (36) of the activation energy barriers, which allow the easy determination of the oriented EEF conditions requested to switch between kinetic control selectivities. In practice, this novel visual tool can “only” be generated using the FDBβ methodology (otherwise, it becomes computationally prohibitive even for medium-sized systems).
Finally, another benefit of this research has been the analysis of the viability (37) of the oriented EEF as a synthetic strategy to obtain elusive cycloadducts. For instance, the exo′/endo′ cycloadducts in the (3 + 2) cycloadditions and the [5,6]-bond attack DA product between C60 and a diene.

(3 + 2) Cycloaddition between Azomethine Ylide and Nitrostyrene

The 1,3-dipolar cycloadditions, also known as Huisgen cycloadditions, have become a versatile route for the regio- and stereoselective construction of five-membered rings. (38) As the first test of our FDBβ methodology, we selected the (3 + 2) cycloaddition between N-benzylidene-glycinate and β-nitrostyrene, which has been thoroughly studied both experimentally and computationally. (39) Depending on the experimental conditions, two ylides can be formed from the imide, yielding to four possible cycloadducts, namely, endo, exo, endo′, and exo′ (see Scheme 1). With usual heating and solvent, only the stereoisomers endo and exo are formed. (40) When the reaction is carried out without solvent, both in thermal or microwave conditions, a mixture of exo, endo, and endo′ cycloadducts is obtained. (40) Finally, the exo′ product has been synthesized catalyzing the reaction with consensus tetratricopeptide repeat proteins in tetrahydrofuran solution, which generates the four pyrrolidine stereoisomers in equimolar ratio. (41)

Scheme 1

Scheme 1. Studied (3 + 2) Cycloaddition Reaction between Azomethine Ylide and Nitrostyrene with the Four Possible Cycloadducts
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Our computational results for this reaction are fully consistent with previous studies. (40,41) Without the presence of an EEF, using a Boltzmann distribution over the activation energy barriers of the different cycloadducts obtained, the ratios 5.3:2.9:1.8:0 for the endo, exo, endo′, and exo′ are predicted, respectively.
Herein, the orientation of the nitrostyrene is fixed, and the two ylides are placed in the proper orientation to deliver each of the four possible cycloadducts. The z-axis is defined as the reaction axis; the olefinic double bond delimits the y-axis, and the direction where the phenyl group of the nitrostyrene is located indicates the positive region for both the x and y-axes (see Scheme 1).
Turning on an oriented EEF along the z-axis, the reaction can be either catalyzed or inhibited; see Figure 1. The field-induced catalysis/inhibition is controlled by the nucleophilicity–electrophilicity of the reactants triggered by the electronic density changes that the molecules suffer caused by the EE. As Shaik and co-workers have reported in several articles, (1c) the aforementioned field-induced changes in the electronic density are sometimes easily tracked by measuring the dipole moment of the transition-state geometries. For instance, for the endo pathway, when an EEF with Fz > 0 is applied, the reaction energy barrier decreases and the dipole moment module of the TS increases from 2.10 to 2.96 au. The increase in field-induced TS dipole moment illustrates the increase of the electron transfer from the highest occupied molecular orbital (HOMO) of the diene to the lowest unoccupied molecular orbital (LUMO) of the dienophile, which is the cause of the reduction of the cycloaddition activation barrier. The opposite is true when Fz < 0 is applied, and the dipole moment module of the TS decreases, resulting in an increase of the energy barrier. This rationalization can also be performed for all of the studied reactions (see Figures SI1 and SI2).

Figure 1

Figure 1. Activation energy barriers for the (3 + 2) cycloaddition between azomethine ylide and nitrostyrene (kcal·mol–1) in terms of the applied EEF z-axis. Dashed lines represent the prediction using FDBβ. Solid lines correspond to the explicit optimization of the reactants, products, and TSs in the presence of an EEF. Calculations were performed at the B3LYP-D3BJ/6-311+G(2d,2p)//B3LYP-D3BJ/6-31+G(d,p) level of theory.

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In Figure 1, for field strengths between −5 × 10–3 and 5 × 10–3 au, we found excellent agreement between the predictions obtained with the FDBβ methodology and the results obtained reoptimizing the geometry of the reactants and TSs for each given value of EEFs. As expected, higher deviations are found using large field strengths, although the FDBβ approach still provides reliable and fast estimations of the field-dependent energy barriers.
The four TSs present different polarities along the y-axis, and thus, this (3 + 2) cycloaddition may present electric-field-induced selectivity switches (EFISSs) when an EEF is placed along this axis. The activation energy barriers for all of the isomers, except exo′, increase when a positive or negative EEF is applied along the y-axis (Figure 2). Conversely, the energy barrier of the exo′ cycloadduct decreases (increases) for positive (negative) EEF. Then, for a Fy = 5 × 10–3 au, an EFISS occurs and the elusive exo′ cycloadduct can be achieved as the major product. Consequently, at 120 °C, the aforementioned field-free 5.3:2.9:1.8:0 ratio for the endo, exo, endo′, and exo′ cycloadducts, respectively, completely switches into 0.1:0.1:0:9.8 at Fy = 1 × 10–2 au. Additionally, the oriented EEF along the x-axis also presents some interesting reactivity features (see Figure SI3). For instance, for Fx > 0, the endo (major product under free-field conditions) selectivity increases. On the other hand, at Fx = −19 × 10–4 au, an EFISS occurs between the activation energy barriers of the endo and exo (the second major product under free-field conditions) cycloadducts, which leads to an exo selectivity. Then, the oriented EEF could be used for the regio- and stereo-controlled synthesis of the five-membered rings obtained from 1,3-dipolar cycloadditions.

Figure 2

Figure 2. Activation energy barriers for the (3 + 2) cycloaddition between azomethine ylide and nitrostyrene (kcal·mol–1) in terms of the applied EEF y-axis. See Figure 1 caption for additional details.

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From a computational cost point of view, the evaluation of the kinetic barriers for four regioisomers with N EEFs of different strengths and orientations (positive and negative) along all three directions of space implies the optimization of 24N + 8 stationary points. On the other hand, using the FDBβ methodology, the same information can be generated computing only the corresponding electrical properties of the field-free reactants and TSs stationary points. Thus, using the FDBβ methodology, 24N optimization of the geometry of the field-dependent stationary points is avoided, implying a considerable computational reduction cost. Nevertheless, it is important to note that the FDBβ approach considers that the same reaction mechanism holds for any combination of EEF strengths placed in the x, y, and z-axes. For instance, it does not take into account the possibility that a concerted cycloaddition mechanism can become a stepwise process. The stabilization of the zwitterionic or radical intermediate and the mechanistic crossover usually occur with strong oriented EEF. In these situations, the valence bond model can be a useful tool to provide physical insight to rationalize the mechanistic crossover. (1c,25)
Figure 3 illustrates the accuracy obtained using different possible truncations of eq 4 for the exo cycloadduct in terms of the strength of a y-axis EEF. The consideration of only the linear term leads to a wrong prediction of the activation barrier in the presence of Fy, which shows a clear nonlinear dependence. However, it is worth noting that the absolute errors are <3 kcal·mol–1 (see Figure SI4). The incorporation of αel into the model improves substantially the prediction, and a reasonable semiquantitative picture is already obtained. In this particular case, the improvement of the βel term in the Taylor series is negligible. Nevertheless, we recommend including this term routinely in the Taylor series, especially, when α and β can be analytically calculated with an acceptable computational cost.

Figure 3

Figure 3. Activation energy barriers for the (3 + 2) cycloaddition between azomethine ylide and nitrostyrene (kcal·mol–1) for the exo cycloadduct in terms of y-axis EEF. Dotted and dashed lines represent several levels of truncation of eq 4. See Figure 1 caption for additional details.

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Up to this point, only electronic terms were considered in the definition of μ, α, and β of eq 4. However, the inclusion of nuclear relaxation (nr) contribution to α leads to an improved description of the field-dependent barriers, reducing the error down to <0.5 kcal·mol–1 (see Figures 3 and SI4). Thus, and as expected, a progressive and systematic enhancement of the prediction can always be achieved owing to the addition of new terms to the Taylor expansion. As an illustrative example, at Fy = −5 × 103 au, the individual percentage contributions to the activation barrier energy for the μ, αel, αnr, and β terms are −150, 184, 60, and 6%, respectively (see Figure SI5).
As a method based on the Taylor expansion, the FDBβ approximation validity is reduced when the EEF strength increases. Nevertheless, the studies of the reactivity and selectivity induced by EEF often use intensities of the electric fields below 1000 mV·Å–1. Usually, the energy barrier discrepancies between the optimized EEF and the FDBβ approach could be attributed to the nuclear relaxation of the TSs and reactant complexes, which may be partially taken into account by the FDBβ approach including the nuclear relaxation contribution to the polarizability in the Taylor expansion. An indication of the nuclear relaxation relevance is given by the presence of low frequencies in the infrared spectrum.
Overall, the FDBβ approximation including only the electronic contributions to of μ, α, and β provides a mean error for activation energy barriers of all four cycloadducts lower than 1.0 kcal·mol–1. Therefore, this methodology has been selected to study the field-catalyzed reactivity throughout this work.

Diels–Alder Reaction between Maleic Anhydride and Cyclopentadiene

In 1928, Diels and Alder’ seminal work (42) introduces the (4 + 2) cycloaddition between 1,3-dienes and a substituted alkene, the Diels–Alder (DA) reaction. This cycloaddition allows the regio- and stereo-controlled synthesis of cyclohexene derivatives. (43) One of the archetypal DA cycloadditions is the reaction between maleic anhydride and cyclopentadiene (Scheme 2). (44) For this reaction, the effects of oriented EEFs have thoroughly been studied both from theoretical (4,45) and experimental (3d) points of view. Then, for comparison purposes, this reaction has been selected to check the FDBβ performance and to introduce the 2D representation of the chemical barriers for the kinetic product of the reaction.

Scheme 2

Scheme 2. Studied DA Reaction between Maleic Anhydride and Cyclopentadiene
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As Shaik and co-workers reported, (4) under free-field conditions, the formation of both endo and exo cycloadducts is exergonic by −15.4 and −16.1 kcal·mol–1, respectively, and the activation energy barriers for the formation of these products are 15.5 and 16.7 kcal·mol–1, respectively. Assuming that the reaction is kinetically driven, the endo cycloadduct is obtained as the major product under free-field conditions.
In a similar way to the previous example, applying an EEF along the reaction axis (z-axis) catalyzes (Fz < 0) or inhibits (Fz > 0) the endo and exo pathways (Figure 4). At large Fz strengths, the energy barrier discrepancies found between the optimized EEF and the FDBβ approximation are due to the stabilization of a zwitterionic intermediate. (4) If a y-axis EEF is applied, an EFISS is found at Fy ≤ −5 × 10–3 au (0.257 V·Å–1 or 1.29 × 1012 W·cm–2), where the DA reaction presents exo selectivity (Figure 5). The endo barrier is barely affected within the scanned range of electric field strengths, whereas the exo one is modified by almost 6 kcal·mol–1. As reported elsewhere, (46) the secondary orbital interactions (SOI) play a key role in the endo product stabilization at free field. At Fy ≤ 0 au, the destabilization of the endo product with respect to the exo occurs due to the energy increase of the orbital responsible for the stabilizing SOI (for more details, see Figure SI6 and the discussion therein). For this reaction, the FDBβ approach also presents a robust performance, i.e., the mean absolute error (MAE) with respect to the energy profile obtained optimizing with explicit EEFs is <1 kcal·mol–1 and the maximum error is <2 kcal·mol–1.

Figure 4

Figure 4. Activation energy barriers for the endo and exo DA pathways between maleic anhydride and cyclopentadiene (kcal·mol–1) in terms of z-axis EEF. Calculations performed at the B3LYP/6-311++G(d,p)//BP86/6-31+G(d) level of theory. See Figure 1 caption for additional details.

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Figure 5

Figure 5. Activation energy barriers for the endo and exo DA cycloaddition between maleic anhydride and cyclopentadiene (kcal·mol–1) in terms of y-axis EEF. See Figure 4 caption for additional details.

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Taking advantage of the low FDBβ computational cost, it is possible to generate 2D representations summarizing the effects of the combination of any strength of the y- and z-axis EEFs (Figure 6). The red (green) region corresponds to the range of Fz and Fy for which the endo (exo) barrier is lower than the exo (endo) barrier. The intensity of the color and the isocontour lines indicate the magnitude of the activation energy barriers of the kinetically most favored reaction in kcal·mol–1. Isocontour lines are not equidistant, indicating a nonlinear dependence of the chemical barrier with respect to EEF. For the same reason, the border from endo to exo selectivity regions is not linear (see Figure SI7 for the 2D representation using only the linear μ term in eq 4).

Figure 6

Figure 6. Two-dimensional representation of the chemical barriers for the major kinetic product of the DA reaction between maleic anhydride and cyclopentadiene in terms of EEFs along the y and z-axes using the FDBβ approach. Green and red zones indicate exo and endo kinetic selectivities, respectively. Calculations are performed at the B3LYP/6-311++G(d,p)//BP86/6-31+G(d) level of theory. Isoenergy barrier lines in kcal·mol–1.

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In addition, it is worth noting that the endo energy barriers are barely affected by the value of Fy (in agreement with Figure 5), as expected considering the small dipole moment along the y-axis of the endo TS structure.
From this 2D representation, it is also possible to define some novel reactivity EEF concepts. For instance, the EFISS curve defines the set of all vectors that switch the selectivity. In this particular case, the EFISS curve is given by all (Fy,Fz) vectors that switch from endo to exo selectivities. Additionally, it is possible to determine the vector with the minimum module within the set, MEFISS. In Figure 6, MEFISS is represented as a black dot at Fz = 0 au and Fy = −5.8 × 10–3 au. Another important point to remark is that the three-dimensional (3D) representations are also easy to achieve, for instance, performing several (Fy,Fz) 2D plots with different constant Fx values (for an illustrative example, see Figure SI8).
To catalyze or inhibit a reaction, usually, the most relevant orientation is the reaction coordinate. (47) However, the reaction pathways can become quite complex and their regioselectivity, stereoselectivity, and enantioselectivity cannot be controlled by placing the electric field in only one direction. For these systems, the 2D and 3D representations using the FDBβ approach are valuable tools to predict the electric-field-induced reactivity. Additionally, external electric fields can be used to simulate the local electric fields induced by charged functional groups and metal ions, which increases the reaction rate and controls the selectivity of organocatalytic reactions catalyzed by enzymes and zeolites. (1)
Representing these 2D (or 3D) plots using explicit field-dependent optimizations of the reactants and TSs requires an enormous computational cost. For instance, the optimization of (4N)2 + 4 field-dependent stationary points is required to plot the corresponding version of Figure 6, where N is the number of selected EEF strengths (positive and negative). On the other hand, using the FDBβ approximations, representing Figure 6 only requires the optimization of four field-free stationary points and the calculation of their corresponding electrical properties, which implies a (4N2 + 1)-fold computational cost reduction. In addition, here, is important to remark that for such kind of 2D plots, N should be somewhat large to obtain an acceptable resolution.
Finally, the representation of the homologous eq 4 but expanding in a Taylor series, the field-dependent reaction energies instead of the energy barriers shows that the exothermicity of both reactions (endo and exo) increases for the same EEFs for which the corresponding energy barrier decreases, i.e., Fz < 0 (see Figure SI9). Thus, the relationship between field-dependent kinetics and thermodynamics follows the trend given by the Bell–Evans–Polanyi principle. (48)

(3 + 2) Cycloaddition between Methoxyethene and Phenyl Diazomethane

As another example to illustrate the potential of the FDBβ approach, we select a (3 + 2) cycloaddition for which oriented EFFs are potentially able to tune the selectivity between four possible cycloadducts (endo, endo′, exo, and exo′). For this purpose, we choose as reactants a 1,3-diene and a dipolarophile with clear polar characters, i.e., the 1,3-dipolar reaction between phenyl diazomethane and methyl vinyl ether (Scheme 3). The molecular orientation is defined as follows: z-axis was set to be the reaction axis, y-axis to be parallel to the olefin double bond and positive in the direction of the methoxy substituent, and the x-axis is negative in the zone where the methoxy group is located.

Scheme 3

Scheme 3. Studied 1,3-Dipolar Cycloaddition between Phenyl Diazomethane and Methoxyethene and the Four Possible Cycloadducts; Definition of the Cartesian Coordinates for the Reaction
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Under free-field conditions, the exo pathway presents the lowest activation energy barrier (19.8 kcal·mol–1), while the endo, exo′, and endo′ pathways are located at 0.2, 1.4, and 1.7 kcal·mol–1 above it, respectively. Then, at room temperature, the four cycloadducts present the 5.4:3.8:0.5:0.3 (exo/endo/exo′/endo′) ratios.
For Fx > 0, the endo kinetic selectivity is enhanced, whereas the activation energy barriers increase for the other regioisomers (Figure 7). On the contrary, for 0 > Fx > −6.2 × 10–3 au, the exo energy barrier is the lowest one, whereas exo′ cycloadduct becomes the kinetic product of the reaction for Fx < −6.2 × 10–3 au. In this manner, only by varying the intensity of the EEF in the x-axis, one achieves as the major product the endo, exo, or exo′ cycloadducts, passing through two different EFISSs along the path.

Figure 7

Figure 7. Activation energy barriers for (3 + 2) dipolar reactions between phenyl diazomethane and methoxyethene (kcal·mol–1) in terms of the applied x-axis EEF. See Figure 1 caption for additional details.

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For Fy > 0, the exo selectivity is enhanced with respect to endo pathway (Figure 8), whereas the change with respect to the strength of the EEF of endo′ and exo′ activation energy barriers is very small. On the other hand, for Fy < 0, the endo and exo pathways are inhibited, and then at Fy = −102 au, the endo′ and exo′ become the only kinetically feasible cycloadducts. Finally, the EEF along the reaction axis (Fz) catalyzes or inhibits the endo and exo pathways in a similar way (for more details, see Figure SI10).

Figure 8

Figure 8. Activation energy barriers for the (3 + 2) dipolar reaction between phenyl diazomethane and methoxyethene (kcal·mol–1) in terms of the applied y-axis EEF. See Figure 1 caption for additional details.

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A visual summary 2D representation of the activation energy barriers for the major kinetic cycloadduct using any combination of any Fx and Fy strengths is displayed in Figure 9. Under field-free conditions, the exo and endo energy barriers are almost isoenergetic and present the lowest activation energy barriers. From a general perspective, the exo selectivity can be enhanced by negative Fx and positive Fy. The kinetic endo selectivity can be obtained using positive Fx. On the other hand, using negative Fx and Fy electric fields, the major kinetic cycloadduct becomes the exo′ product. Finally, the endo′ cycloadduct, which is the most elusive product under field-free conditions, can be obtained as a major kinetic product applying Fy < −5.0 × 10–3 au and moderate positive Fx.

Figure 9

Figure 9. Two-dimensional representation of the activation energy barriers for the major kinetic product of the (3 + 2) dipolar reaction between phenyl diazomethane and methoxyethene in terms of the applied EEFs along the x- and y-axes using the FDBβ approach. Green, red, blue, and orange zones indicate exo, endo, exo′, and endo′ kinetic selectivities, respectively. Black dots indicate the MEFISS points. Calculations are performed at the B3LYP-D3BJ/6-311+G(2d,2p)//B3LYP-D3BJ/6-31+G(d,p) level of theory. Isoenergy barrier lines in kcal·mol–1.

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Figure 9 also shows five EFISS curves corresponding to the exo/endo, exo/exo′, endo/endo′, endo/exo′, and exo′/endo′ selectivity switches and four MEFISSs (indicated as black dots). Herein, it is important to underline that the exo, endo, exo′, and endo′ selectivities can be tuned at will using relatively small EEF window values, i.e., −25 × 10–4 < Fx < 10–4 and −60 × 10–4 < Fy < 0 au. Additionally, the 2D plot generated with the FDBβ approach also illustrates that the dependence of the barriers in terms of the strength of the applied EEF is nonlinear (see also Figure SI11) since both the displayed isocontour lines and the EFISS curves are not straight lines.
As in the previous example, it is also possible to generate several (Fx,Fy) 2D plots with different constant Fz strengths. As indicated previously, the EEF along the reaction coordinate modifies the magnitude of the activation energy barrier (catalyze or inhibit) but not the selectivity. Consequently, not relevant differences are found with respect to Figure 9 (see Figure SI12). Again, it is important to remark that the generation of Figure 9 using explicit field-dependent equilibrium geometry optimizations requires the calculation of (8N)2 + 8 stationary points, where N is the number of selected positive and negative EEF strengths. On the other hand, the FDBβ approximations only requires the optimization of eight field-free stationary points and the calculation of their corresponding electrical properties. Therefore, for a reaction with four possible products, FDBβ is (8N2 + 1)-fold cheaper in terms of CPU time than the usual methodology. A detailed summary of the computational cost benefits of the FDBβ approximation can be found in Table SI2.

Diels–Alder Reaction between C60 and Cyclopentadiene

As a last example, we select a reaction involving 65 carbon atoms, the DA reaction between C60 fullerene and cyclopentadiene. (49) Under field-free conditions, the energy barrier of this DA cycloaddition is lower for [6,6]- than for [5,6]-bonds (Scheme 4). (50) The Diels–Alder [5,6] functionalization has never been reported experimentally for the DA cycloadditions to C60, although theoretically it was found possible in highly reduced C60 (51) or in the high-spin states of C60. (52) Herein, we explore the potential of the oriented EEF as a synthetic strategy to obtain the elusive [5,6]-bond cycloadduct.

Scheme 4

Scheme 4. Schematic Representation of DA Reaction over a [6,6]- (Top) or [5,6]-Bond (Bottom) of a C60 Fullerene Represented by One of Its Corannulene Unit, Respectively
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The reactant complex is oriented so that the z-axis is parallel to the reaction coordinate, and either the attacked [5,6]- or the [6,6]-bond defines the y-axis (Scheme 4). The reactivity is almost not changing when an EEF is applied either along the x- or y-axis (see Figures SI13 and S14 for more details); therefore, only the z-axis results are discussed herein. For Fz > 0 (Fz < 0) au, the FDBβ approach predicts that the activation energy barriers are increasing (decreasing) for both pathways (Figure 10). The role of the EEF on this reaction can be rationalized by analyzing the effect of the electric field on the HOMO and LUMO. The presence of a negative (positive) pole of the EEF located above (below) the diene (C60) destabilizes (stabilizes) the HOMO (LUMO) mainly located in the cyclopentadiene (C60), which favors the reaction and then decreases the energy barrier.

Figure 10

Figure 10. Activation energy barriers of the DA between C60 and cyclopentadiene (kcal·mol–1) in terms of the applied z-axis EEF. Solid lines are calculated at the B3LYP-D3BJ/6-311+G(2d,2p)//B3LYP-D3BJ/6-31+G(d,p) level of theory using the FDBβ approximation. Color dots correspond to explicit field-dependent geometrical optimizations performed for a specific EEF.

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For Fz < 0, the decrease of the activation energy barriers is more pronounced for the [5,6]-bond than for the [6,6]-bond pathway, implying a reduction of the gap between the two activation barriers, although no EFISS is observed in the studied range. At Fz = 10–2 au, the FDBβ approach estimates a gap difference between both pathways of only 3 kcal·mol–1, a reduction of 9 kcal·mol–1 with respect to the free-field conditions. To check the validity of this conclusion, optimizations of the reactants and TSs at Fz = −10–2 au were performed. The results displayed in Figure 10 confirm the FDBβ results, although there is a difference of 2.5 kcal·mol–1 between the difference in the energy barriers obtained with both methodologies. Thus, we conclude that for Fz < −10–2 au and high temperatures, some traces of the [5,6]-cycloadduct in the product mixture could be found.

Conclusions

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A novel methodology to estimate activation energy barriers in the presence of external electric fields (EEFs) is reported herein. The FDBβ approach is based on the Taylor expansion of the field-dependent energy of the reactants and transition states (TSs) in terms of their dipole moments and electrical (hyper)polarizabilities. As illustrative examples, to assess the reliability and validity of the proposed method, we have studied the effect of EEFs on four reactions (two 1,3-dipolar and two Diels–Alder cycloadditions).
The FDBβ approach only requires the geometry optimizations of the reactants and TSs under free-field conditions, and the calculation of their (hyper)polarizabilities. Thus, no explicit EEF calculations are required. The obtained results indicate that estimations of the activation energy barriers for different EEF strengths can be obtained with errors usually smaller than 1 kcal·mol–1. Additionally, the consideration of only the electronic contribution to the electrical (hyper)polarizabilities is sufficient to recover most of the changes in the activation energy barriers. Nevertheless, if it is required, the inclusion of nuclear relaxation contribution to the polarizability, which can be obtained from a single frequency calculation, further improves the quality of the energy barrier estimations.
The benefits of the FDBβ methodology are its simplicity and the massive reduction of the CPU-time cost with respect to the explicit optimizations of the reactant complexes and transition states for several EEF strengths. The FDBβ approach permits systematic 1D, 2D, and 3D representations of the activation energy barriers for any strength and direction of the EEFs. Furthermore, one can determine which is the optimum strength and direction of an EEF required to induce a particular selectivity switch. Thus, the FDBβ approach can be used to “seek and identify” the potential synthesis using EEF of elusive regioisomers, which cannot be obtained under other experimental conditions. For instance, for the studied 1,3-dipolar reaction between methoxyethene and phenyl diazomethane, the four possible cycloadducts can be obtained as major kinetic control products by changing only the magnitudes and directions of Fx and Fy.
To conclude, we believe that the FDBβ approach can be used as a fast-screening tool to predict novel potential field-induced catalysis and regioselectivities, especially for systems of organocatalytic and biocatalytic interests that involve a large number of atoms.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acscatal.1c04247.

  • Nuclear relaxation contribution assessment; dipole moment changes in TS structures; MAE for several FDB approaches; 1D representations of the EEF-induced chemical barriers for the remaining directions and cycloadditions indicated but not reported in the manuscript; DA secondary orbital interaction analysis; 2D maps for different FDB approaches and for several Fz EEFs for the DA maleic anhydride and cyclopentadiene and the (3 + 2) cycloaddition between azomethine ylide and nitrostyrene; CPU time required using the explicit optimization of reactant complexes and transition states in the presence of an EEF and using the FDBβ approach; and Cartesian coordinates (PDF)

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Author Information

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  • Corresponding Authors
    • Josep M. Luis - Institut de Química Computacional i Catàlisi and Departament de Química, Universitat de Girona, Campus de Montilivi, 17003 Girona, Catalonia, Spain;  Orcidhttps://orcid.org/0000-0002-2880-8680;  Email: [email protected]
    • Miquel Torrent-Sucarrat - Department of Organic Chemistry I, Centro de Innovación en Química Avanzada (ORFEO-CINQA), Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU) and Donostia International Physics Center (DIPC), P Manuel Lardizabal 3, E-20018 Donostia/San Sebastián, Euskadi, Spain;  Ikerbasque, Basque Foundation for Science, Plaza Euskadi 5, 48009 Bilbao, Euskadi, Spain;  Orcidhttps://orcid.org/0000-0003-2689-0278;  Email: [email protected]
  • Authors
    • Pau Besalú-Sala - Institut de Química Computacional i Catàlisi and Departament de Química, Universitat de Girona, Campus de Montilivi, 17003 Girona, Catalonia, Spain;  Orcidhttps://orcid.org/0000-0002-0955-9762
    • Miquel Solà - Institut de Química Computacional i Catàlisi and Departament de Química, Universitat de Girona, Campus de Montilivi, 17003 Girona, Catalonia, Spain;  Orcidhttps://orcid.org/0000-0002-1917-7450
  • Author Contributions

    M.T.-S., M.S., and J.M.L. devised and supervised the project. P.B-S. performed all calculations and analyzed the results. The manuscript was written through the contributions of all authors. All authors approved the final version of the manuscript.

  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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This work was supported with funds from the Ministerio de Economía y Competitividad (MINECO) of Spain (project CTQ2017-85341-P to M.S.), the Spanish government MICINN (projects PGC2018-098212-B-C22 to J.M.L, PID2020-113711GB-I00 to M.S., and PID2019-104772GB-I00 to M.T.S.), the Generalitat de Catalunya (project 2017SGR39 to M.S. and J.M.L.), and Gobierno Vasco (project IT1346-19 to M.T.S.). The authors thank the Spanish government for the predoctoral grant to P.B.-S. (FPU17/02058). They are also grateful for the computational time financed by the Consorci de Serveis Universitaris de Catalunya (CSUC). They thank the reviewers for their comments and helpful suggestions.

References

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This article references 52 other publications.

  1. 1
    (a) Shaik, S.; Mandal, D.; Ramanan, R. Oriented Electric Fields as Future Smart Reagents in Chemistry. Nat. Chem. 2016, 8, 1091– 1098,  DOI: 10.1038/nchem.2651
    Google Scholar
    1a
    Oriented electric fields as future smart reagents in chemistry
    Shaik, Sason; Mandal, Debasish; Ramanan, Rajeev
    Nature Chemistry (2016), 8 (12), 1091-1098CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)
    A review. Oriented external elec. fields (OEEFs) as smart reagents are no longer a theor. dream. Here, the wide-ranging potential of using OEEFs to catalyze and control a variety of nonredox reactions and impart selectivity at will are discussed. An OEEF along the direction of electron reorganization (the so-called reaction axis) will catalyze nonpolar reactions by orders of magnitude, control regioselectivity and induce spin-state selectivity. Simply flipping the direction of the OEEF or orienting it off of the reaction axis, will control at will the endo/exo ratio in Diels-Alder reactions and steps in enzymic cycles. This Perspective highlights these outcomes using theor. results for hydrogen abstraction reactions, epoxidn. of double bonds, C-C bond forming reactions, proton transfers and the cycle of the enzyme cytochrome P 450, as well as recent exptl. data. The authors postulate that, as exptl. techniques mature, chem. syntheses may become an exercise in zapping oriented mols. with OEEFs.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXht1Oru70%253D&md5=0869a9db7fd24142210e4c696aebc811
    (b) Che, F.; Gray, J. T.; Ha, S.; Kruse, N.; Scott, S. L.; McEwen, J.-S. Elucidating the Roles of Electric Fields in Catalysis: A Perspective. ACS Catal. 2018, 8, 5153– 5174,  DOI: 10.1021/acscatal.7b02899
    Google Scholar
    1b
    Elucidating the Roles of Electric Fields in Catalysis: A Perspective
    Che, Fanglin; Gray, Jake T.; Ha, Su; Kruse, Norbert; Scott, Susannah L.; McEwen, Jean-Sabin
    ACS Catalysis (2018), 8 (6), 5153-5174CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
    A review. This Perspective illustrates how the presence of internal and external elec. fields can affect catalytic activity and selectivity, with a focus on heterogeneous catalysts. Specifically, exptl. studies of the elec. field influence on catalyst selectivity in pulsed field mass desorption microscopes, scanning tunneling microscopes, probe-bed-probe reactors, continuous-circuit reactors, and capacitor reactors are described. Through these examples, the elec. field, whether externally applied or intrinsically present, can affect the behavior of a wide no. of materials relevant to catalysis. The authors review some of the theor. methods that were used to elucidate the influence of external elec. fields on catalytic reactions, as well as the application of such methods to selective methane activation. In doing so, the authors illustrate the breadth of possibilities in field-assisted catalysis.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXmslGqsb4%253D&md5=e73298ae055cc34207b58f59a4c535f3
    (c) Shaik, S.; Ramanan, R.; Danovich, D.; Mandal, D. Structure and Reactivity/Selectivity Control by Oriented-External Electric Fields. Chem. Soc. Rev. 2018, 47, 5125– 5145,  DOI: 10.1039/C8CS00354H
    Google Scholar
    1c
    Structure and reactivity/selectivity control by oriented-external electric fields
    Shaik, Sason; Ramanan, Rajeev; Danovich, David; Mandal, Debasish
    Chemical Society Reviews (2018), 47 (14), 5125-5145CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
    This is a tutorial on use of external-elec.-fields (EEFs) as effectors of chem. change. The tutorial instructs readers how to conceptualize and design elec.-field effects on bonds, structures, and reactions. Most effects can be comprehended as the field-induced stabilization of ionic structures. Thus, orienting the field along the "bond axis" will facilitate bond breaking. Similarly, orienting the field along the "reaction axis", the direction in which "electron pairs transform" from reactants- to products-like, will catalyze the reaction. Flipping the field's orientation along the reaction-axis will cause inhibition. Orienting the field off-reaction-axis will control stereo-selectivity and remove forbidden-orbital mixing. Two-directional fields may control both reactivity and selectivity. Increasing the field strength for concerted reactions (e.g., Diels-Alder's) will cause mechanistic-switchover to stepwise mechanisms with ionic intermediates. Examples of bond breaking and control of reactivity/selectivity and mechanisms are presented and analyzed from the "ionic perspective". The tutorial projects the unity of EEF effects, "giving insight and nos.".
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXht1OjtL3K&md5=f56f13e624805dfb6d36b7951fd1a008
    (d) Robertson, J. C.; Coote, M. L.; Bissember, A. C. Synthetic Applications of Light, Electricity, Mechanical Force and Flow. Nat. Rev. Chem. 2019, 3, 290– 304,  DOI: 10.1038/s41570-019-0094-2
    Google Scholar
    There is no corresponding record for this reference.
    (e) Shaik, S.; Danovich, D.; Joy, J.; Wang, Z.; Stuyver, T. Electric-Field Mediated Chemistry: Uncovering and Exploiting the Potential of (Oriented) Electric Fields to Exert Chemical Catalysis and Reaction Control. J. Am. Chem. Soc. 2020, 142, 12551– 12562,  DOI: 10.1021/jacs.0c05128
    Google Scholar
    1e
    Electric-Field Mediated Chemistry: Uncovering and Exploiting the Potential of (Oriented) Electric Fields to Exert Chemical Catalysis and Reaction Control
    Shaik, Sason; Danovich, David; Joy, Jyothish; Wang, Zhanfeng; Stuyver, Thijs
    Journal of the American Chemical Society (2020), 142 (29), 12551-12562CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    A review. This Perspective discusses oriented external-elec.-fields (OEEF), and other elec.-field types, as "smart reagents", which enable in principle control over wide-ranging aspects of reactivity and structure. We discuss the potential of OEEFs to control nonredox reactions and impart rate-enhancement and selectivity. An OEEF along the "reaction axis", which is the direction whereby electronic reorganization converts reactants' to products' bonding, will accelerate reactions, control regioselectivity, induce spin-state selectivity, and elicit mechanistic crossovers. Simply flipping the direction of the OEEF will lead to inhibition. Orienting the OEEF off the reaction axis enables control over stereoselectivity, enantioselectivity, and product selectivity. For polar/polarizable reactants, the OEEF itself will act as tweezers, which orient the reactants and drive their reaction. OEEFs also affect bond-dissocn. energies and dissocn. modes (covalent vs ionic), as well as alteration of mol. geometries and supramol. aggregation. The "key" to gaining access to this toolbox provided by OEEFs is microscopic control over the alignment between the mol. and the applied field. We discuss the elegant exptl. methods which have been used to verify the theor. predictions and describe various alternative EEF sources and prospects for upscaling OEEF catalysis in solvents. We also demonstrate the numerous ways in which the OEEF effects can be mimicked by use of (designed) local-elec. fields (LEFs), i.e., by embedding charges or dipoles into mols. LEFs and OEEFs are shown to be equiv. and to obey the same ground rules. Outcomes are exemplified for Diels-Alder cycloaddns., oxidative addn. of bonds by transition-metal complexes, H-abstractions by oxo-metal species, ionic cleavage of halogen bonds, methane activation, etc.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXht1SltrfI&md5=da09d2fc434aaf5b926696e0d980a572
    (f) Léonard, N. G.; Dhaoui, R.; Chantarojsiri, T.; Yang, J. Y. Electric Fields in Catalysis: From Enzymes to Molecular Catalysts. ACS Catal. 2021, 10923– 10932,  DOI: 10.1021/acscatal.1c02084
    Google Scholar
    1f
    Electric Fields in Catalysis: From Enzymes to Molecular Catalysts
    Leonard, Nadia G.; Dhaoui, Rakia; Chantarojsiri, Teera; Yang, Jenny Y.
    ACS Catalysis (2021), 11 (17), 10923-10932CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
    A review. Elec. fields underlie all reactions and impact reactivity by interacting with the dipoles and net charges of transition states, products, and reactants to modify the free energy landscape. However, they are rarely given deliberate consideration in synthetic design to rationally control reactivity. This Perspective discusses the commonalities of elec. field effects across multiple platforms, from enzymes to mol. catalysts, and identifies practical challenges to applying them in synthetic mol. systems to mediate reactivity.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXhvVSqsr%252FK&md5=8576b0ab2c1e711625bc66c79af64e43
  2. 2
    (a) Bhattacharyya, D.; Videla, P. E.; Cattaneo, M.; Batista, V. S.; Lian, T.; Kubiak, C. P. Vibrational Stark Shift Spectroscopy of Catalysts under the Influence of Electric Fields at Electrode–Solution Interfaces. Chem. Sci. 2021, 12, 10131– 10149,  DOI: 10.1039/D1SC01876K
    Google Scholar
    2a
    Vibrational Stark shift spectroscopy of catalysts under the influence of electric fields at electrode-solution interfaces
    Bhattacharyya, Dhritiman; Videla, Pablo E.; Cattaneo, Mauricio; Batista, Victor S.; Lian, Tianquan; Kubiak, Clifford P.
    Chemical Science (2021), 12 (30), 10131-10149CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
    A review. External control of chem. processes is a subject of widespread interest in chem. research, including control of electrocatalytic processes with significant promise in energy research. The electrochem. double-layer is the nanoscale region next to the electrode/electrolyte interface where chem. reactions typically occur. Understanding the effects of elec. fields within the electrochem. double layer requires a combination of synthesis, electrochem., spectroscopy, and theory. In particular, vibrational sum frequency generation (VSFG) spectroscopy is a powerful technique to probe the response of mol. catalysts at the electrode interface under bias. Fundamental understanding can be obtained via synthetic tuning of the adsorbed mol. catalysts on the electrode surface and by combining exptl. VSFG data with theor. modeling of the Stark shift response. The resulting insights at the mol. level are particularly valuable for the development of new methodologies to control and characterize catalysts confined to electrode surfaces. This Perspective article is focused on how systematic modifications of mols. anchored to surfaces report information concerning the geometric, energetic, and electronic parameters of catalysts under bias attached to electrode surfaces.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXhsFensb3K&md5=494089d9c0949a7f7fc6f51ccd2f0874
    (b) Concellón, A.; Lu, R.-Q.; Yoshinaga, K.; Hsu, H.-F.; Swager, T. M. Electric-Field-Induced Chirality in Columnar Liquid Crystals. J. Am. Chem. Soc. 2021, 143, 9260– 9266,  DOI: 10.1021/jacs.1c05268
    Google Scholar
    2b
    Electric-Field-Induced Chirality in Columnar Liquid Crystals
    Concellon, Alberto; Lu, Ru-Qiang; Yoshinaga, Kosuke; Hsu, Hsiu-Fu; Swager, Timothy M.
    Journal of the American Chemical Society (2021), 143 (24), 9260-9266CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    We describe a novel class of tetraphenylbenzene-based discotic mols. with exceptional self-assembling properties. Absorption and fluorescence studies confirmed the formation of J-type aggregates in soln. The discotic mesogens also show an enhancement of the emission upon aggregation. Interestingly, these discotic mols. displayed enantiotropic hexagonal columnar liq. crystal (LC) phases that can be switched into a helical columnar organization by application of an elec. field. The helical columns arise from the elec.-field-induced tilt of the polar fluorobenzene ring that directs all of the peripheral Ph groups into a propeller-like conformation with respect to the central benzene core. A cooperative assembly process of these propeller-shaped mols. resolves into a helical columnar organization, in which the preferred helical sense is obtained from the stereogenic center proximate to the polar carbon-fluorine bond. The ease of inducing chirality in columnar LCs by an elec. field presents opportunities to create next-generation chiral materials for a variety of applications.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXht1Orur7O&md5=f6471e3858dfe838d390c5459e7ebf05
    (c) Kawasaki, T.; Kaimori, Y.; Shimada, S.; Hara, N.; Sato, S.; Suzuki, K.; Asahi, T.; Matsumoto, A.; Soai, K. Asymmetric Autocatalysis Triggered by Triglycine Sulfate with Switchable Chirality by Altering the Direction of the Applied Electric Field. Chem. Commun. 2021, 57, 5999– 6002,  DOI: 10.1039/D1CC02162A
    Google Scholar
    2c
    Asymmetric autocatalysis triggered by triglycine sulfate with switchable chirality by altering the direction of the applied electric field
    Kawasaki, Tsuneomi; Kaimori, Yoshiyasu; Shimada, Seiya; Hara, Natsuki; Sato, Susumu; Suzuki, Kenta; Asahi, Toru; Matsumoto, Arimasa; Soai, Kenso
    Chemical Communications (Cambridge, United Kingdom) (2021), 57 (49), 5999-6002CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    Triglycine sulfate (TGS) acts as a chiral trigger for asym. autocatalysis with amplification of enantiomeric excess, i.e., the Soai reaction. Therefore, mol. chirality of highly enantioenriched org. compds. is controlled by a ferroelec. crystal TGS, whose polarization is altered by an elec. field.
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    (d) Nakamura, K.; Sugiura, S.; Araoka, F.; Aya, S.; Takanishi, Y.; Watanabe, G.; Sato, R.; Shigeta, Y.; Maeda, H. Conformation-Changeable π-Electronic Systems with Metastable Bent-Core Conformations and Liquid-Crystalline-State Electric-Field-Responsive Properties. Org. Lett. 2021, 23, 305– 310,  DOI: 10.1021/acs.orglett.0c03791
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    2d
    Conformation-Changeable π-Electronic Systems with Metastable Bent-Core Conformations and Liquid-Crystalline-State Electric-Field-Responsive Properties
    Nakamura, Kazuto; Sugiura, Shinya; Araoka, Fumito; Aya, Satoshi; Takanishi, Yoichi; Watanabe, Go; Sato, Ryuma; Shigeta, Yasuteru; Maeda, Hiromitsu
    Organic Letters (2021), 23 (2), 305-310CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
    This study focused on the use of nonconventional bent-core π-electronic systems, 2,2'-bipyrroles substituted with modified benzoyl units, as building units of stimuli-responsive assemblies. Elec.-field-responsive mesophase behaviors were obsd. in homochiral synclinic ferroelec. smectic C structures comprising the syn conformations. Elec.-field application induced changes in the polarized optical microscopy textures with dynamic behaviors derived from the conversion from twisted to untwisted states.
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    (e) Yu, Z.; Wang, L.; Mu, X.; Chen, C.-C.; Wu, Y.; Cao, J.; Tang, Y. Intramolecular Electric Field Construction in Metal Phthalocyanine as Dopant-Free Hole Transporting Material for Stable Perovskite Solar Cells with >21% Efficiency. Angew. Chem., Int. Ed. 2021, 60, 6294– 6299,  DOI: 10.1002/anie.202016087
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    2e
    Intramolecular Electric Field Construction in Metal Phthalocyanine as Dopant-Free Hole Transporting Material for Stable Perovskite Solar Cells with >21 % Efficiency
    Yu, Zefeng; Wang, Luyao; Mu, Xijiao; Chen, Chun-Chao; Wu, Yiying; Cao, Jing; Tang, Yu
    Angewandte Chemie, International Edition (2021), 60 (12), 6294-6299CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Low cond. and hole mobility in the pristine metal phthalocyanines greatly limit their application in perovskite solar cells (PSCs) as the hole-transporting materials (HTMs). Here, we prep. a Ni phthalocyanine (NiPc) decorated by four methoxyethoxy units as HTMs. In NiPc, the two oxygen atoms in peripheral substituent have a modified effect on the dipole direction, while the central Ni atom contributes more electron to phthalocyanine ring, thus efficiently increasing the intramol. dipole. Calcn. analyses reveal the extd. holes within NiPc are mainly concd. on the phthalocyanine core induced by the intramol. elec. field, and further to be transferred by π-π stacking space channel between NiPc mols. Finally, the best efficiency of PSCs with NiPc as dopant-free HTMs realizes a record value of 21.23 % (certified 21.03 %). The PSCs also exhibit the good moisture, heating and light stabilities. This work provides a novel way to improve the performance of PSCs with free-doped metal phthalocyanines as HTMs.
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  3. 3
    (a) Suydam, I. T.; Snow, C. D.; Pande, V. S.; Boxer, S. G. Electric Fields at the Active Site of an Enzyme: Direct Comparison of Experiment with Theory. Science 2006, 313, 200– 204,  DOI: 10.1126/science.1127159
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    3a
    Electric Fields at the Active Site of an Enzyme: Direct Comparison of Experiment with Theory
    Suydam, Ian T.; Snow, Christopher D.; Pande, Vijay S.; Boxer, Steven G.
    Science (Washington, DC, United States) (2006), 313 (5784), 200-204CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
    The elec. fields produced in folded proteins influence nearly every aspect of protein function. We present a vibrational spectroscopy technique that measures changes in elec. field at a specific site of a protein as shifts in frequency (Stark shifts) of a calibrated nitrile vibration. A nitrile-contg. inhibitor is used to deliver a unique probe vibration to the active site of human aldose reductase, and the response of the nitrile stretch frequency is measured for a series of mutations in the enzyme active site. These shifts yield quant. information on elec. fields that can be directly compared with electrostatics calcns. We show that extensive mol. dynamics simulations and ensemble averaging are required to reproduce the obsd. changes in field.
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    (b) Gorin, C. F.; Beh, E. S.; Kanan, M. W. An Electric Field–Induced Change in the Selectivity of a Metal Oxide–Catalyzed Epoxide Rearrangement. J. Am. Chem. Soc. 2012, 134, 186– 189,  DOI: 10.1021/ja210365j
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    3b
    An Electric Field-Induced Change in the Selectivity of a Metal Oxide-Catalyzed Epoxide Rearrangement
    Gorin, Craig F.; Beh, Eugene S.; Kanan, Matthew W.
    Journal of the American Chemical Society (2012), 134 (1), 186-189CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    The rearrangement of cis-stilbene oxide catalyzed by Al2O3 was studied in the presence of interfacial elec. fields. Thin films of Al2O3 deposited on Si electrodes were used as the opposing walls of a reaction vessel. Application of a voltage across the electrodes engendered electrochem. double layer formation at the Al2O3-soln. interface. The aldehyde to ketone product ratio of the rearrangement was increased by up to a factor of 63 as the magnitude of the double layer charge d. was increased. The results support a field-dipole effect on the selectivity of the catalytic reaction.
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    (c) Gorin, C. F.; Beh, E. S.; Bui, Q. M.; Dick, G. R.; Kanan, M. W. Interfacial Electric Field Effects on a Carbene Reaction Catalyzed by Rh Porphyrins. J. Am. Chem. Soc. 2013, 135, 11257– 11265,  DOI: 10.1021/ja404394z
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    3c
    Interfacial Electric Field Effects on a Carbene Reaction Catalyzed by Rh Porphyrins
    Gorin, Craig F.; Beh, Eugene S.; Bui, Quan M.; Dick, Graham R.; Kanan, Matthew W.
    Journal of the American Chemical Society (2013), 135 (30), 11257-11265CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    An intramol. reaction catalyzed by Rh porphyrins was studied in the presence of interfacial elec. fields. 1-Diazo-3,3-dimethyl-5-phenylhex-5-en-2-one (2) reacts with Rh porphyrins via a putative carbenoid intermediate to form cyclopropanation product 3,3-dimethyl-5-phenylbicyclo[3.1.0]hexan-2-one (3) and insertion product 3,3-dimethyl-2,3-dihydro-[1,1'-biphenyl]-4(1H)-one (4). To study this reaction in the presence of an interfacial elec. field, Si electrodes coated with thin films of insulating dielec. layers were used as the opposing walls of a reaction vessel, and Rh porphyrin catalysts were localized to the dielec.-electrolyte interface. The charge d. was varied at the interface by changing the voltage across the two electrodes. The product ratio was analyzed as a function of the applied voltage and the surface chem. of the dielec. layer. In the absence of an applied voltage, the ratio of 3:4 was ∼10:1. With a TiO2 surface, application of a voltage induced a Rh porphyrin-TiO2 interaction that resulted in an increase in the 3:4 ratio to a max. in which 4 was nearly completely suppressed (>100:1). With an Al2O3 surface or an alkylphosphonate-coated surface, the voltage caused a decrease in the 3:4 ratio, with a max. effect of lowering the ratio to 1:2. The voltage-induced decrease in the 3:4 ratio in the absence of TiO2 was consistent with a field-dipole effect that changed the difference in activation energies for the product-detg. step to favor product 4. Effects were obsd. for porphyrin catalysts localized to the electrode-electrolyte interface either through covalent attachment or surface adsorption, enabling the selectivity to be controlled with unfunctionalized Rh porphyrins. The magnitude of the selectivity change was limited by the max. interfacial charge d. that could be attained before dielec. breakdown.
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    (d) Aragonès, A. C.; Haworth, N. L.; Darwish, N.; Ciampi, S.; Bloomfield, N. J.; Wallace, G. G.; Diez-Perez, I.; Coote, M. L. Electrostatic Catalysis of a Diels–Alder Reaction. Nature 2016, 531, 88– 91,  DOI: 10.1038/nature16989
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    3d
    Electrostatic catalysis of a Diels-Alder reaction
    Aragones, Albert C.; Haworth, Naomi L.; Darwish, Nadim; Ciampi, Simone; Bloomfield, Nathaniel J.; Wallace, Gordon G.; Diez-Perez, Ismael; Coote, Michelle L.
    Nature (London, United Kingdom) (2016), 531 (7592), 88-91CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)
    It is often thought that the ability to control reaction rates with an applied elec. potential gradient is unique to redox systems. However, recent theor. studies suggest that oriented elec. fields could affect the outcomes of a range of chem. reactions, regardless of whether a redox system is involved. This possibility arises because many formally covalent species can be stabilized via minor charge-sepd. resonance contributors. When an applied elec. field is aligned in such a way as to electrostatically stabilize one of these minor forms, the degree of resonance increases, resulting in the overall stabilization of the mol. or transition state. This means that it should be possible to manipulate the kinetics and thermodn. of non-redox processes using an external elec. field, as long as the orientation of the approaching reactants with respect to the field stimulus can be controlled. Here, we provide exptl. evidence that the formation of carbon-carbon bonds is accelerated by an elec. field. We have designed a surface model system to probe the Diels-Alder reaction, and coupled it with a scanning tunnelling microscopy break-junction approach. This technique, performed at the single-mol. level, is perfectly suited to deliver an elec.-field stimulus across approaching reactants. We find a fivefold increase in the frequency of formation of single-mol. junctions, resulting from the reaction that occurs when the elec. field is present and aligned so as to favor electron flow from the dienophile to the diene. Our results are qual. consistent with those predicted by quantum-chem. calcns. in a theor. model of this system, and herald a new approach to chem. catalysis.
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    (e) Olavarría-Contreras, I. J.; Etcheverry-Berríos, A.; Qian, W.; Gutiérrez-Cerón, C.; Campos-Olguín, A.; Sañudo, E. C.; Duli, D.; Ruiz, E.; Aliaga-Alcalde, N.; Soler, M.; van der Zant, H. S. J. Electric-Field Induced Bistability in Single-Molecule Conductance Measurements for Boron Coordinated Curcuminoid Compounds. Chem. Sci. 2018, 9, 6988– 6996,  DOI: 10.1039/C8SC02337A
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    3e
    Electric-field induced bistability in single-molecule conductance measurements for boron coordinated curcuminoid compounds
    Olavarria-Contreras, Ignacio Jose; Etcheverry-Berrios, Alvaro; Qian, Wenjie; Gutierrez-Ceron, Cristian; Campos-Olguin, Aldo; Sanudo, E. Carolina; Dulic, Diana; Ruiz, Eliseo; Aliaga-Alcalde, Nuria; Soler, Monica; van der Zant, Herre S. J.
    Chemical Science (2018), 9 (34), 6988-6996CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
    We have studied the single-mol. conductance of a family of curcuminoid mols. (CCMs) using the mech. controlled break junction (MCBJ) technique. The CCMs under study contain methylthio (MeS-) as anchoring groups: MeS-CCM (1), the free-ligand org. mol., and two coordination compds., MeS-CCM-BF2 (2) and MeS-CCM-Cu (3), where ligand 1 coordinates to a boron center (BF2 group) and to a CuII moiety, resp. We found that the three mols. present stable mol. junctions allowing detailed statistical anal. of their electronic properties. Compd. 3 shows a slight increase in the conductance with respect to free ligand 1, whereas incorporation of BF2 (compd. 2) promotes the presence of two conductance states in the measurements. Addnl. expts. with control mols. point out that this bistability is related to the combination of MeS- anchoring groups and the BF2 moiety within the structure of the mols. Theor. calcns. show that this can be explained by the presence of two conformers once compd. 2 is anchored between the gold electrodes. An energy min. is found for a flat structure but there is a dramatic change in the magnitude and orientation of dipole moment (favoring a non-flat conformer in the presence of an external elec. field) due to a conformational change of one of the terminal MeS- groups. The results thus point to an intricate interplay between the applied bias voltage and the mol. dipole moment which could be the basis for designing new mols. aiming at controlling their conformation in devices.
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    (f) Huang, X.; Tang, C.; Li, J.; Chen, L.-C.; Zheng, J.; Zhang, P.; Le, J.; Li, R.; Li, X.; Liu, J.; Yang, Y.; Shi, J.; Chen, Z.; Bai, M.; Zhang, H.-L.; Xia, H.; Cheng, J.; Tian, Z.-Q.; Hong, W. Electric Field–Induced Selective Catalysis of Single-Molecule Reaction. Sci. Adv. 2019, 5, eaaw3072  DOI: 10.1126/sciadv.aaw3072
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    (g) Zang, Y.; Zou, Q.; Fu, T.; Ng, F.; Fowler, B.; Yang, J.; Li, H.; Steigerwald, M. L.; Nuckolls, C.; Venkataraman, L. Directing Isomerization Reactions of Cumulenes with Electric Fields. Nat. Commun. 2019, 10, 4482  DOI: 10.1038/s41467-019-12487-w
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    3g
    Directing isomerization reactions of cumulenes with electric fields
    Zang Yaping; Venkataraman Latha; Zou Qi; Fu Tianren; Ng Fay; Fowler Brandon; Yang Jingjing; Steigerwald Michael L; Nuckolls Colin; Venkataraman Latha; Zou Qi; Li Hexing
    Nature communications (2019), 10 (1), 4482 ISSN:.
    Electric fields have been proposed as having a distinct ability to catalyze chemical reactions through the stabilization of polar or ionic intermediate transition states. Although field-assisted catalysis is being researched, the ability to catalyze reactions in solution using electric fields remains elusive and the understanding of mechanisms of such catalysis is sparse. Here we show that an electric field can catalyze the cis-to-trans isomerization of [3]cumulene derivatives in solution, in a scanning tunneling microscope. We further show that the external electric field can alter the thermodynamics inhibiting the trans-to-cis reverse reaction, endowing the selectivity toward trans isomer. Using density functional theory-based calculations, we find that the applied electric field promotes a zwitterionic resonance form, which ensures a lower energy transition state for the isomerization reaction. The field also stabilizes the trans form, relative to the cis, dictating the cis/trans thermodynamics, driving the equilibrium product exclusively toward the trans.
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    (h) Tang, Y.; Zhou, Y.; Zhou, D.; Chen, Y.; Xiao, Z.; Shi, J.; Liu, J.; Hong, W. Electric Field-Induced Assembly in Single-Stacking Terphenyl Junctions. J. Am. Chem. Soc. 2020, 142, 19101– 19109,  DOI: 10.1021/jacs.0c07348
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    3h
    Electric Field-Induced Assembly in Single-Stacking Terphenyl Junctions
    Tang, Yongxiang; Zhou, Yu; Zhou, Dahai; Chen, Yaorong; Xiao, Zongyuan; Shi, Jia; Liu, Junyang; Hong, Wenjing
    Journal of the American Chemical Society (2020), 142 (45), 19101-19109CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Mol. assembly is crucial in functional mol. materials and devices. Among the mol. interactions that can form assemblies, stacking among π-conjugated mol. backbones plays an essential role in charge transport through org. materials and devices. The single-mol. junction technique allows for the application of an elec. field of approx. 108 V/m to the nanoscale junctions and to investigate the elec. field-induced assembly at the single-stacking level. Here, we demonstrate an elec. field-induced stacking effect between two mols. using the scanning tunneling microscope break junction (STM-BJ) technique and we found an increase in the stacking probability with increasing intensity of the elec. field. The combined d. functional theory (DFT) calcns. suggest that the mols. become more planar under the elec. field, leading to the energetically preferred stacking configuration. Our study provides a new strategy for tuning mol. assembly by employing a strong elec. field.
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    (i) Gao, T.; Pan, Z.; Cai, Z.; Zheng, J.; Tang, C.; Yuan, S.; Zhao, S. q.; Bai, H.; Yang, Y.; Shi, J.; Xiao, Z.; Liu, J.; Hong, W. Electric Field-Induced Switching among Multiple Conductance Pathways in Single-Molecule Junctions. Chem. Commun. 2021, 57, 7160– 7163,  DOI: 10.1039/D1CC02111G
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    3i
    Electric field-induced switching among multiple conductance pathways in single-molecule junctions
    Gao, Tengyang; Pan, Zhichao; Cai, Zhuanyun; Zheng, Jueting; Tang, Chun; Yuan, Saisai; Zhao, Shi qiang; Bai, Hua; Yang, Yang; Shi, Jia; Xiao, Zongyuan; Liu, Junyang; Hong, Wenjing
    Chemical Communications (Cambridge, United Kingdom) (2021), 57 (58), 7160-7163CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    Here, we report the switching among multiple conductance pathways achieved by sliding the scanning tunneling microscope tip among different binding sites under different elec. fields. With an increase in the elec. field, high mol. conductance states appear, suggesting the formation of different configurations in single-mol. junctions. The switch can be operated in situ and reversibly, which is also confirmed by the apparent conductance conversion in I-V measurements. Theor. simulations also agree well with the exptl. results, which implies that the elec. field enables the possibility to trigger switching in single-mol. junctions.
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  4. 4
    Meir, R.; Chen, H.; Lai, W.; Shaik, S. Oriented Electric Fields Accelerate Diels–Alder Reactions and Control the endo/exo Selectivity. ChemPhysChem 2010, 11, 301– 310,  DOI: 10.1002/cphc.200900848
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    4
    Oriented Electric Fields Accelerate Diels-Alder Reactions and Control the endo/exo Selectivity
    Meir, Rinat; Chen, Hui; Lai, Wenzhen; Shaik, Sason
    ChemPhysChem (2010), 11 (1), 301-310CODEN: CPCHFT; ISSN:1439-4235. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Herein an external elec. field (EEF) acts as an accessory catalyst/inhibitor for Diels-Alder (DA) reactions. When the EEF is oriented along the reaction axis (the coordinate of approach of the reactants in the reaction path), the barrier of the DA reactions is lowered by a significant amt., equiv. to rate enhancements by 4-6 orders of magnitude. Simply flipping the EEF direction has the opposite effect, and the EEF acts as an inhibitor. Addnl., an EEF oriented perpendicular to the reaction axis in the direction of the individual mol. dipoles can change the endo/exo selectivity, favoring one or the other depending on the pos./neg. directions of the EEF vis-a-vis the individual mol. dipole. At some crit. value of the EEF along the reaction axis, there is a crossover to a stepwise mechanism that involves a zwitterionic intermediate. The valence bond diagram model is used to comprehend these trends and to derive a selection rule for EEF effects on chem. reactions: an EEF aligned in the direction of the electron flow between the reactants will lower the reaction barrier. The exo/endo control by the EEF is not assocd. with changes in secondary orbital interactions.
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  5. 5
    (a) Andrés, J. L.; Lledós, A.; Duran, M.; Bertrán, J. Electric Fields Acting as Catalysts in Chemical Reactions. An ab Initio Study of the Walden Inversion Reaction. Chem. Phys. Lett. 1988, 153, 82– 86,  DOI: 10.1016/0009-2614(88)80136-2
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    5a
    Electric fields acting as catalysts in chemical reactions. An ab initio study of the Walden inversion reaction
    Andres, J. L.; Lledos, A.; Duran, M.; Bertran, J.
    Chemical Physics Letters (1988), 153 (1), 82-6CODEN: CHPLBC; ISSN:0009-2614.
    Ab initio SCF calcns. were carried out on the F- exchange reaction F- + CH3F → FCH3 + F-. An external uniform elec. field along the FCF axis was incorporated by proper changes in the 1-electron part of the Fock matrix. The reaction profile is dramatically modified with increase in strength of the applied field. The elec. field is essential to describe the potential energy hypersurface so that it intervenes in the reaction coordinate. Strong elec. fields therefore open a new way to catalyze reactions.
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    (b) Carbonell, E.; Duran, M.; Lledós, A.; Bertrán, J. Catalysis of Friedel-Crafts Reactions by Electric Fields. J. Phys. Chem. A. 1991, 95, 179– 183,  DOI: 10.1021/j100154a036
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    5b
    Catalysis of Friedel-Crafts reactions by electric fields
    Carbonell, Emili; Duran, Miquel; Lledos, Agusti; Bertran, Juan
    Journal of Physical Chemistry (1991), 95 (1), 179-83CODEN: JPCHAX; ISSN:0022-3654.
    The effects of uniform and nonuniform elec. fields on the HF + CH4 reaction are examd. by using an ab initio RHF method with the 3-21+G basis set. Barrier heights and positions of stationary points along the reaction coordinate are dramatically altered upon introduction of such elec. fields. The changes are analyzed in terms of modifications in at. charges and variations of electron densities at the main bond crit. points. The elec. fields belong to the reaction coordinate of this chem. process.
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    (c) Bhattacharyya, K.; Karmakar, S.; Datta, A. External electric field control: driving the reactivity of metal-free azide–alkyne click reactions. Phys. Chem. Chem. Phys. 2017, 19, 22482– 22486,  DOI: 10.1039/C7CP04202G
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    5c
    External electric field control: driving the reactivity of metal-free azide-alkyne click reactions
    Bhattacharyya, Kalishankar; Karmakar, Sharmistha; Datta, Ayan
    Physical Chemistry Chemical Physics (2017), 19 (33), 22482-22486CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    Recent reports have suggested that an external elec. field (EEF) can assist and even control product selectivity. In this work, we have shown that the barrier for the Huisgen reaction between alkyl (aryl) azide and cyclooctyne(biflurocyclooctyne) is reduced by ∼3-4 kcal mol-1 when an oriented EEF is applied along the reaction axis. As a consequence of their inherently polar transition-states (TSs), a parallel orientation of the EEF results in enhancement of the charge transfer (CT) between the fragments and concomitant increase in the dipole moment along the reaction axes. This leads to an increase in the reaction rate for moderate EEFs in the range of 0.3-0.5 V Å-1. Since highly polar and directional environments are omnipresent in biol. environments, metal-free click reactions can be further accelerated for non-invasive imaging of live-cells. Conceptually, elec. field control appears to be a novel tool (catalyst) to drive, and possibly even tune, the reactivity of org. mols.
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    (d) Gryn’ova, G.; Coote, M. L. Directionality and the Role of Polarization in Electric Field Effects on Radical Stability. Aust. J. Chem. 2017, 70, 367– 372,  DOI: 10.1071/CH16579
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    5d
    Directionality and the Role of Polarization in Electric Field Effects on Radical Stability
    Gryn'ova, Ganna; Coote, Michelle L.
    Australian Journal of Chemistry (2017), 70 (4), 367-372CODEN: AJCHAS; ISSN:0004-9425. (CSIRO Publishing)
    Accurate quantum-chem. calcns. are used to analyze the effects of charges on the kinetics and thermodn. of radical reactions, with specific attention given to the origin and directionality of the effects. Conventionally, large effects of the charges are expected to occur in systems with pronounced charge-sepd. resonance contributors. The nature (stabilization or destabilization) and magnitude of these effects thus depend on the orientation of the interacting multipoles. However, we show that a significant component of the stabilizing effects of the external elec. field is largely independent of the orientation of external elec. field (e.g. a charged functional group, a point charge, or an electrode) and occurs even in the absence of any pre-existing charge sepn. This effect arises from polarization of the electron d. of the mol. induced by the elec. field. This polarization effect is greater for highly delocalized species such as resonance-stabilized radicals and transition states of radical reactions. We show that this effect on the stability of such species is preserved in chem. reaction energies, leading to lower bond-dissocn. energies and barrier heights. Finally, our simplified modeling of the diol dehydratase-catalyzed 1,2-hydroxyl shift indicates that such stabilizing polarization is likely to contribute to the catalytic activity of enzymes.
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    (e) Welborn, V. V.; Ruiz Pestana, L.; Head-Gordon, T. Computational Optimization of Electric Fields for Better Catalysis Design. Nat. Catal. 2018, 1, 649– 655,  DOI: 10.1038/s41929-018-0109-2
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    (f) Acosta-Silva, C.; Bertran, J.; Branchadell, V.; Oliva, A. Kemp Elimination Reaction Catalyzed by Electric Fields. ChemPhysChem 2020, 21, 295– 306,  DOI: 10.1002/cphc.201901155
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    5f
    Kemp Elimination Reaction Catalyzed by Electric Fields
    Acosta-Silva, Carles; Bertran, Joan; Branchadell, Vicenc; Oliva, Antoni
    ChemPhysChem (2020), 21 (4), 295-306CODEN: CPCHFT; ISSN:1439-4235. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The Kemp elimination reaction is the most widely used in the de novo design of new enzymes. The effect of two different kinds of elec. fields in the reactions of acetate as a base with benzisoxazole and 5-nitrobenzisoxazole as substrates have been theor. studied. The effect of the solvent reaction field has been calcd. using the SMD continuum model for several solvents; we have shown that solvents inhibit both reactions, the decrease of the reaction rate being larger as far as the dielec. const. is increased. The diminution of the reaction rate is esp. remarkable between aprotic org. solvents and protic solvents as water, the electrostatic term of the hydrogen bonds being the main factor for the large inhibitory effect of water. The presence of an external elec. field oriented in the direction of the charge transfer (z axis) increases it and, so, the reaction rate. In the reaction of the nitro compd., if the elec. field is oriented in an orthogonal direction (x axis) the charge transfer to the NO2 group is favored and there is a subsequent increase of the reaction rate. However, this increase is smaller than the one produced by the field in the z axis. It is worthwhile mentioning that one of the main effects of external elec. fields of intermediate intensity is the reorientation of the reactants. Finally, the implications of our results in the de novo design of enzymes are discussed.
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    (g) Stuyver, T.; Shaik, S. Resolving Entangled Reactivity Modes through External Electric Fields and Substitution: Application to E2/SN2 Reactions. J. Org. Chem. 2021, 86, 9030– 9039,  DOI: 10.1021/acs.joc.1c01010
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    5g
    Resolving Entangled Reactivity Modes through External Electric Fields and Substitution: Application to E2/SN2 Reactions
    Stuyver, Thijs; Shaik, Sason
    Journal of Organic Chemistry (2021), 86 (13), 9030-9039CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)
    In this study, we explore strategies to resolve entangled reactivity modes. More specifically, we consider the competition between SN2 and E2 reaction pathways for alkyl halides and nucleophiles/bases. We first demonstrate that the emergence of an E2-preference is assocd. with an enhancement of the magnitude of the resonance stabilization in the transition-state (TS) region, resulting from the improved mixing of electrostatically stabilized valence bond structures into the TS wavefunction. Subsequently, we show that the TS resonance energy can be tuned selectively and rationally either through the application of an oriented external elec. field directed along the C-C axis of the alkyl halide or through a regular substitution approach of the C-C moiety. We end our study by demonstrating that the insights gained from our anal. enable one to rationalize the main reactivity trends emerging from a recently published large database of competing SN2 and E2 reaction pathways.
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  6. 6
    Hill, N. S.; Coote, M. L. Internal Oriented Electric Fields as a Strategy for Selectively Modifying Photochemical Reactivity. J. Am. Chem. Soc. 2018, 140, 17800– 17804,  DOI: 10.1021/jacs.8b12009
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    6
    Internal Oriented Electric Fields as a Strategy for Selectively Modifying Photochemical Reactivity
    Hill, Nicholas S.; Coote, Michelle L.
    Journal of the American Chemical Society (2018), 140 (50), 17800-17804CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Time-dependent d. functional theory calcns. were performed on acetophenone derivs. to explore the possibility of using charged functional groups as internal elec. fields, the orientation of which can be altered to change photochem. behavior at will. Nonconjugated charged groups can significantly alter, by up to -1.44 eV, the stabilities of excited states. Specifically, a nonconjugated neg. charged group in the para position will destabilize the nπ* and stabilize the ππ* transitions, while a pos. charged group will do the opposite. These electrostatic effects can be tuned by moving these substituents into the meta and ortho positions. Through use of acids and bases, these charged groups can be switched on or off with pH, allowing for selective alteration of the energy levels and photochem. reactivity. Solvent effects attenuate the elec. field effect with increasing dielec. permittivity; however electrostatic effects remain significant even in quite polar solvents. Using charged functional groups to deliver the position-dependent electrostatic (de)stabilization effects is therefore a potential route to improving the efficiency of desirable photochem. processes.
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  7. 7
    Jaroš, A.; Bonab, E. F.; Straka, M.; Foroutan-Nejad, C. Fullerene-Based Switching Molecular Diodes Controlled by Oriented External Electric Fields. J. Am. Chem. Soc. 2019, 141, 19644– 19654,  DOI: 10.1021/jacs.9b07215
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    7
    Fullerene-Based Switching Molecular Diodes Controlled by Oriented External Electric Fields
    Jaros, Adam; Bonab, Esmaeil Farajpour; Straka, Michal; Foroutan-Nejad, Cina
    Journal of the American Chemical Society (2019), 141 (50), 19644-19654CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Employing multi-scale in silico modeling we propose switching mol. diodes on the basis of endohedral fullerenes (fullerene switching diode, FSD), encapsulated with polar mols. of general type MX (M: metal, X: non-metal) to be used for data storage and processing. Here, we demonstrate for MX@C70 systems that the relative orientation of enclosed MX with respect to a set of electrodes connected to the system can be controlled by application of oriented external elec. field(s). We suggest systems with two- and four-terminal electrodes, in which the source and drain electrodes help the current to pass through the device and help the switching between the conductive states of FSD via applied voltage. The gate electrodes then assist the switching by effectively lowering the energy barrier between local min. via stabilizing the transition state of switching process if the applied voltage between the source and drain is insufficient to switch the MX inside the fullerene. Using non-equil. Green's function combined with d. functional theory (DFT-NEGF) computations, we further show that cond. of the studied MX@C70 systems depends on the relative orientation of MX inside the cage with respect to the electrodes. Therefore, the orientation of the MX inside C70 can be both enforced ("written") and retrieved ("read") by applied voltage. The studied systems thus behave like voltage-sensitive switching mol. diodes, that is a reminiscent of a mol. memristor.
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  8. 8
    Kirshenboim, O.; Frenklah, A.; Kozuch, S. Switch Chemistry at Cryogenic Conditions: Quantum Tunnelling under Electric Fields. Chem. Sci. 2021, 12, 3179– 3187,  DOI: 10.1039/D0SC06295B
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    8
    Switch chemistry at cryogenic conditions: quantum tunnelling under electric fields
    Kirshenboim, Omer; Frenklah, Alexander; Kozuch, Sebastian
    Chemical Science (2021), 12 (9), 3179-3187CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
    While the influence of intramol. elec. fields is a known feature in enzymes, the use of oriented external elec. fields (EEF) to enhance or inhibit mol. reactivity is a promising topic still in its infancy. Herein we will explore computationally the effects that EEF can provoke in simple mols. close to the abs. zero, where quantum tunnelling (QT) is the sole mechanistic option. We studied three exemplary systems, each one with different reactivity features and known QT kinetics: π bond-shifting in pentalene, Cope rearrangement in semibullvalene, and cycloreversion of diazabicyclohexadiene. The kinetics of these cases depend both on the field strength and its direction, usually giving subtle but remarkable changes. However, for the cycloreversion, which suffers large changes on the dipole through the reaction, we also obsd. striking results. Between the effects caused by the EEF on the QT we obsd. an inversion of the Arrhenius equation, deactivation of the mol. fluxionality, and stabilization or instantaneous decompn. of the system. All these effects may well be achieved, literally, at the flick of a switch.
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  9. 9
    (a) Lei, Y. K.; Zhang, J.; Zhang, Z.; Gao, Y. Q. Dynamic Electric Field Complicates Chemical Reactions in Solutions. J. Phys. Chem. Lett. 2019, 10, 2991– 2997,  DOI: 10.1021/acs.jpclett.9b01038
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    9a
    Dynamic Electric Field Complicates Chemical Reactions in Solutions
    Lei, Yao Kun; Zhang, Jun; Zhang, Zhen; Gao, Yi Qin
    Journal of Physical Chemistry Letters (2019), 10 (11), 2991-2997CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    Chem. reactions can be strongly influenced by an external elec. field (EEF), but because the EEF is often time-dependent and in case it does not adapt quickly enough to the reaction progress, esp. during fast barrier crossing processes, dynamic effects could be important. Here we find that electrostatic interactions can reduce the height of the reaction barrier for a Claissen rearrangement reaction and accelerate the key motions for bonding. Meanwhile, strong electrostatic interactions can modify the barrier into an effective potential well, confining the system into the barrier until solvents adjust themselves to provide an appropriate EEF for charge redistribution. In this case, the otherwise concerted mechanism becomes a stepwise one. Consequently, the motion of solvents modulates the reaction dynamics and leads to heterogeneous reaction paths, even in a seemingly homogeneous aq. soln. In addn., an excessive stabilization of transition state retards the barrier crossing process, making the thermodynamically favorable pathway less favored dynamically.
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    (b) Mattioli, E. J.; Bottoni, A.; Zerbetto, F.; Calvaresi, M. Oriented External Electric Fields Affect Rate and Stereoselectivity of Electrocyclic Reactions. J. Phys. Chem. C 2019, 123, 26370– 26378,  DOI: 10.1021/acs.jpcc.9b07358
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    9b
    Oriented External Electric Fields Affect Rate and Stereoselectivity of Electrocyclic Reactions
    Mattioli, Edoardo Jun; Bottoni, Andrea; Zerbetto, Francesco; Calvaresi, Matteo
    Journal of Physical Chemistry C (2019), 123 (43), 26370-26378CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    We carried out a computational investigation at the d. functional theory (M06-2X) level on the effects of oriented external elec. fields (OEEF) on activation barriers and stereochem. output of the thermal ring opening of 3-substituted cyclobutenes (C4H5X) to butadienes. It is well known that with π-electron-donor substituents (X = CH3, NH2), the conrotatory outward rotation is preferred, while with π-electron-acceptor substituents (X = CHO, NO, BH2), the conrotatory inward process becomes favored. In the presence of the OEEF applied along the three axes x, y, and z in either pos. or neg. direction, for both π-donor and π-acceptor substituents, we obsd. either catalysis or inhibition. Both effects were consistent with the change of the induced dipole along the direction of the applied field. An interesting effect was obsd. for X = CHO and NO. The simultaneous catalysis and inhibition of the outward and inward transformation leads to a reversed ratio between outward and inward transformation, with the former being favored (stereochem. inversion). Such effect was not obsd. for X = BH2 (the strongest π-acceptor examd. here). In this case, in the absence of the applied field, the difference between the inward and outward barriers is too large and the simultaneous catalysis and inhibition of the outward and inward transformation is not capable of detg. the stereochem. inversion.
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    (c) Shi, M. W.; Thomas, S. P.; Hathwar, V. R.; Edwards, A. J.; Piltz, R. O.; Jayatilaka, D.; Koutsantonis, G. A.; Overgaard, J.; Nishibori, E.; Iversen, B. B.; Spackman, M. A. Measurement of Electric Fields Experienced by Urea Guest Molecules in the 18-Crown-6/Urea (1:5) Host–Guest Complex: An Experimental Reference Point for Electric-Field-Assisted Catalysis. J. Am. Chem. Soc. 2019, 141, 3965– 3976,  DOI: 10.1021/jacs.8b12927
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    9c
    Measurement of Electric Fields Experienced by Urea Guest Molecules in the 18-Crown-6/Urea (1:5) Host-Guest Complex: An Experimental Reference Point for Electric-Field-Assisted Catalysis
    Shi, Ming W.; Thomas, Sajesh P.; Hathwar, Venkatesha R.; Edwards, Alison J.; Piltz, Ross O.; Jayatilaka, Dylan; Koutsantonis, George A.; Overgaard, Jacob; Nishibori, Eiji; Iversen, Bo B.; Spackman, Mark A.
    Journal of the American Chemical Society (2019), 141 (9), 3965-3976CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    High-resoln. synchrotron and neutron single-crystal diffraction data of 18-crown-6/(pentakis)urea measured at 30 K are combined, with the aim of better appreciating the electrostatics assocd. with intermol. interactions in condensed matter. With two 18-crown-6 mols. and five different urea mols. in the crystal, this represents the most ambitious combined X-ray/synchrotron and neutron exptl. charge d. anal. to date on a cocrystal or host-guest system incorporating such a large no. of unique mols. The dipole moments of the five urea guest mols. in the crystal are enhanced considerably compared to values detd. for isolated mols., and 2D maps of the electrostatic potential and elec. field show clearly how the urea mols. are oriented with dipole moments aligned along the elec. field exerted by their mol. neighbors. Exptl. elec. fields in the range of 10-19 GV m-1, obtained for the five different urea environments, corroborate independent measurements of elec. fields in the active sites of enzymes and provide an important exptl. ref. point for recent discussions focused on elec.-field-assisted catalysis.
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    (d) Smolinsky, E. Z. B.; Neubauer, A.; Kumar, A.; Yochelis, S.; Capua, E.; Carmieli, R.; Paltiel, Y.; Naaman, R.; Michaeli, K. Electric Field-Controlled Magnetization in GaAs/AlGaAs Heterostructures–Chiral Organic Molecules Hybrids. J. Phys. Chem. Lett. 2019, 10, 1139– 1145,  DOI: 10.1021/acs.jpclett.9b00092
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    9d
    Electric Field-Controlled Magnetization in GaAs/AlGaAs Heterostructures-Chiral Organic Molecules Hybrids
    Smolinsky, Eilam Z. B.; Neubauer, Avner; Kumar, Anup; Yochelis, Shira; Capua, Eyal; Carmieli, Raanan; Paltiel, Yossi; Naaman, Ron; Michaeli, Karen
    Journal of Physical Chemistry Letters (2019), 10 (5), 1139-1145CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    We study GaAs/AlGaAs devices hosting a two-dimensional electron gas and coated with a monolayer of chiral org. mols. We observe clear signatures of room-temp. magnetism, which is induced in these systems by applying a gate voltage. We explain this phenomenon as a consequence of the spin-polarized charges that are injected into the semiconductor through the chiral mols. The orientation of the magnetic moment can be manipulated by low gate voltages, with a switching rate in the megahertz range. Thus, our devices implement an efficient, elec. field-controlled magnetization, which has long been desired for their tech. prospects.
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    (e) Wang, C.; Danovich, D.; Chen, H.; Shaik, S. Oriented External Electric Fields: Tweezers and Catalysts for Reactivity in Halogen-Bond Complexes. J. Am. Chem. Soc. 2019, 141, 7122– 7136,  DOI: 10.1021/jacs.9b02174
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    9e
    Oriented External Electric Fields: Tweezers and Catalysts for Reactivity in Halogen-Bond Complexes
    Wang, Chao; Danovich, David; Chen, Hui; Shaik, Sason
    Journal of the American Chemical Society (2019), 141 (17), 7122-7136CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    This theor. study establishes ways of controlling and enabling an uncommon chem. reaction, the displacement reaction, B:---(X-Y) → (B-X)+ + :Y-, which is nascent from a B:---(X-Y) halogen bond (XB) by nucleophilic attack of the base, B:, on the halogen, X. In most of the 14 cases examd., these reactions possess high barriers either in the gas phase (where the X-Y bond dissocs. to radicals) or in solvents such as CH2Cl2 and CH3CN (which lead to endothermic processes). Thus, generally, the XB species are trapped in deep min., and their reactions are not allowed without catalysis. However, when an oriented-external elec. field (OEEF) is directed along the B---X---Y reaction axis, the field acts as elec. tweezers that orient the XB along the field's axis, and intensely catalyze the process, by tens of kcal/mol, thus rendering the reaction allowed. Flipping the OEEF along the reaction axis inhibits the reaction and weakens the interaction of the XB. Furthermore, at a crit. OEEF, each XB undergoes spontaneous and barrier-free reaction. As such, OEEF achieves quite tight control of the structure and reactivity of XB species. Valence bond modeling is used to elucidate the means whereby OEEFs exert their control.
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    (f) Yeh, C.-H.; Pham, T. M. L.; Nachimuthu, S.; Jiang, J.-C. Effect of External Electric Field on Methane Conversion on IrO2(110) Surface: A Density Functional Theory Study. ACS Catal. 2019, 9, 8230– 8242,  DOI: 10.1021/acscatal.9b01910
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    9f
    Effect of External Electric Field on Methane Conversion on IrO2(110) Surface: A Density Functional Theory Study
    Yeh, Chen-Hao; Pham, Thong Minh Le; Nachimuthu, Santhanamoorthi; Jiang, Jyh-Chiang
    ACS Catalysis (2019), 9 (9), 8230-8242CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
    Catalytic conversion of methane to value-added chems. is a promising application for gas versatility. In this work, we have investigated the methane oxidn. over oxygen-rich IrO2 (110) surface by DFT calcns., as IrO2 is reported to be an effective catalyst for activating the C-H bond of methane. Compared to the methane reaction on the surface of stoichiometric IrO2 (110), the reaction barrier for each step of forming formaldehyde on the oxygen-rich IrO2 (110) is small. The calcns. show that formaldehyde formation is the most favorable route in methane oxidn., but this process is limited by the high desorption energy of formaldehyde. To modify the reactivity of IrO2 (110), we conducted a study of the influence of an external elec. field on the methane conversion reaction. The calcns. show that the effects of external elec. field on methane dehydrogenation and C-O coupling reactions are not so apparent. However, it is found that the desorption energy of the adsorbates can be regulated by applying an external elec. field. Our study indicates that the use of an external elec. field is crucial in regulating the catalytic reaction, and esp. the application of a pos. elec. field promotes the oxidn. of methane to formaldehyde over oxygen-rich IrO2 (110) surface.
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    (g) Zhang, M.-X.; Xu, H.-L. A Greener Catalyst for Hydroboration of Imines─External Electric Field Modify the Reaction Mechanism. J. Comput. Chem. 2019, 40, 1772– 1779,  DOI: 10.1002/jcc.25830
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    9g
    A greener catalyst for hydroboration of imines-external electric field modify the reaction mechanism
    Zhang, Ming-Xia; Xu, Hong-Liang
    Journal of Computational Chemistry (2019), 40 (19), 1772-1779CODEN: JCCHDD; ISSN:0192-8651. (John Wiley & Sons, Inc.)
    Usually, an extra catalyst (for example, the transition metal complexes) need to be used in catalyzing hydroboration, which involved the cost, environment, and so forth. Here, a greener and controllable catalyst-external elec. field (EEF) was used to study its effect on hydroboration of N-(4-methylbenzyl)aniline (PhN=CHPhMe) with pinacolboane (HBPin). The results demonstrated that EEF could affect the barrier heights of both two pathways of this reaction. More significantly, flipping the direction of EEF could modify the reaction mechanism to induce a dominant inverse hydroboration at some field strength. That is to say, oriented EEF is a controlling switch for the anti- or Markovnikov hydroboration reaction of imines. This investigation is meaningful for the exploration of greener catalyst for chem. reaction and guide a new method for the Markovnikov hydroboration addn.
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    (h) He, C. Q.; Lam, C. C.; Yu, P.; Song, Z.; Chen, M.; Lam, Y.-h.; Chen, S.; Houk, K. N. Catalytic Effects of Ammonium and Sulfonium Salts and External Electric Fields on Aza-Diels–Alder Reactions. J. Org. Chem. 2020, 85, 2618– 2625,  DOI: 10.1021/acs.joc.9b03446
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    9h
    Catalytic Effects of Ammonium and Sulfonium Salts and External Electric Fields on Aza-Diels-Alder Reactions
    He, Cyndi Qixin; Lam, Ching Ching; Yu, Peiyuan; Song, Zhihui; Chen, Maggie; Lam, Yu-hong; Chen, Shuming; Houk, K. N.
    Journal of Organic Chemistry (2020), 85 (4), 2618-2625CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)
    The mechanism of the aza-Diels-Alder reaction catalyzed by tetraalkylammonium or trialkylsulfonium salts is explored with d. functional theory. Favorable electrostatic interactions between the dienophile and the charged catalyst stabilize the highly polar transition state, leading to lower free energy barriers and higher dipole moments. Endo selectivity is predicted for both uncatalyzed and catalyzed systems. We also computationally evaluate the effects of oriented external elec. fields (EEFs) on the same aza-Diels-Alder reaction, demonstrating that very strong EEFs would be needed to achieve the catalytic strength of these cationic catalysts.
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    (i) Wang, W.-W.; Shang, F.-L.; Zhao, X. Curved Carbon Skeleton in Oriented External Electric Fields: Modulated Curvature, Directional Bowl Inversion, and Face-Selective Cycloadditions of Corannulene. Org. Lett. 2020, 22, 4786– 4791,  DOI: 10.1021/acs.orglett.0c01595
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    9i
    Curved Carbon Skeleton in Oriented External Electric Fields: Modulated Curvature, Directional Bowl Inversion, and Face-Selective Cycloadditions of Corannulene
    Wang, Wei-Wei; Shang, Fu-Lin; Zhao, Xiang
    Organic Letters (2020), 22 (12), 4786-4791CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
    We introduced the oriented-external-elec.-field-induced modification of bowl-shaped corannulene using d. functional theory calcns. The results show that the elec. field is capable of significantly modulating the polarization and electrostatic characteristics of the concave and convex surfaces of buckybowls. The structure-energy-reactivity relation can be precisely controlled, leading to a variety of unconventional properties for practical applications.
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    (j) Zhang, R.; Warren, J. J. Controlling the Oxygen Reduction Selectivity of Asymmetric Cobalt Porphyrins by Using Local Electrostatic Interactions. J. Am. Chem. Soc. 2020, 142, 13426– 13434,  DOI: 10.1021/jacs.0c03861
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    9j
    Controlling the Oxygen Reduction Selectivity of Asymmetric Cobalt Porphyrins by Using Local Electrostatic Interactions
    Zhang, Rui; Warren, Jeffrey J.
    Journal of the American Chemical Society (2020), 142 (31), 13426-13434CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    The development and improvement of electrocatalysts for the 4H+/4e- redn. of O2 to H2O is an ongoing challenge. The addn. of ancillary groups (e.g., hydrogen bonding, Bronsted acid/base) near the active site of metal-contg. catalysts is an effective way to improve selectivity and kinetics of the oxygen redn. reaction (ORR). In this regard, iron porphyrins are among the most researched ORR catalysts. Closely related cobalt porphyrin ORR catalysts can function closer to the O2/H2O thermodn. potential, but they tend to be less selective and follow a different mechanism than for the iron porphyrins. Herein, strategies are explored to extend the ideas about ancillary groups that have been developed for iron porphyrin ORR electrocatalysts to improve the performance of the corresponding cobalt complexes. A series of porphyrin electrocatalysts are described that are modified versions of Co(5,10,15,20-tetraphenylporphyrin), where the 2-position of one of the Ph groups contains -NH2, -N(CH3)2, and -N(CH3)3+. Investigations using cyclic voltammetry and hydrodynamic electrochem. show that the presence of a cationic ancillary group gives rise to a catalyst that is selective for the conversion of O2 to H2O across a wide pH range. In contrast, the other catalysts are selective for redn. of O2 to H2O at pH 0, but produce H2O2 at higher pH. The ORR rate (~ 106 M-1 s-1) and selectivity of the -N(CH3)3+-modified catalyst are invariant between pH 0 and 7. Quantum chem. calcns. support the hypothesis that the enhancement of selectivity can be attributed to the distinct mechanism of O2 redn. by Co-porphyrins. Specifically, the mechanism relies on anionic, peroxide-bound intermediates. While protic ancillary groups are important in the performance of iron porphyrin ORR catalysts, it is suggested that electrostatic stabilizers of O2-bound intermediates are more crucial for cobalt porphyrin ORR catalysts.
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    (k) Gheorghiu, A.; Coveney, P. V.; Arabi, A. A. The Influence of External Electric Fields on Proton Transfer Tautomerism in the Guanine–Cytosine Base Pair. Phys. Chem. Chem. Phys. 2021, 23, 6252– 6265,  DOI: 10.1039/D0CP06218A
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    9k
    The influence of external electric fields on proton transfer tautomerism in the guanine-cytosine base pair
    Gheorghiu, Alexander; Coveney, Peter V.; Arabi, Alya A.
    Physical Chemistry Chemical Physics (2021), 23 (10), 6252-6265CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    The Watson-Crick base pair proton transfer tautomers would be widely considered as a source of spontaneous mutations in DNA replication if not for their short lifetimes and thermodn. instability. This work investigates the effects external elec. fields have on the stability of the guanine-cytosine proton transfer tautomers within a realistic strand of aq. DNA using a combination of ensemble-based classical mol. dynamics (MD) coupled to quantum mechanics/mol. mechanics (QM/MM). Performing an ensemble of calcns. accounts for the stochastic aspects of the simulations while allowing for easier identification of systematic errors. The methodol. applied in this work has previously been shown to est. base pair proton transfer rate coeffs. that are in good agreement with recent exptl. data. A range of elec. fields in the order of 104 to 109 V m-1 is investigated based on their real-life medicinal applications which include gene therapy and cancer treatments. The MD trajectories confirm that elec. fields up to 1.00 x 109 V m-1 have a negligible influence on the structure of the base pairs within DNA. The QM/MM results show that the application of large external elec. fields (1.00 x 109 V m-1) parallel to the hydrogen bonds increases the thermodn. population of the tautomers by up to one order of magnitude; moreover, the lifetimes of the tautomers remain insignificant when compared to the timescale of DNA replication.
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    (l) Hennefarth, M. R.; Alexandrova, A. N. Heterogeneous Intramolecular Electric Field as a Descriptor of Diels–Alder Reactivity. J. Phys. Chem. A 2021, 125, 1289– 1298,  DOI: 10.1021/acs.jpca.1c00181
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    9l
    Heterogeneous Intramolecular Electric Field as a Descriptor of Diels-Alder Reactivity
    Hennefarth, Matthew R.; Alexandrova, Anastassia N.
    Journal of Physical Chemistry A (2021), 125 (5), 1289-1298CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
    External elec. fields have proven to be an effective tool in catalysis, on par with pressure and temp., affecting the thermodn. and kinetics of a reaction. However, fields in mols. are complicated heterogeneous vector objects, and there is no universal recipe for grasping the exact features of these fields that implicate reactivity. Herein, we demonstrate that topol. features of the heterogeneous elec. field within the reactant state and of the quantum mech. electron d. - a scalar reporter on the field experienced by the system - can be identified as rigorous descriptors of the reactivity to follow. We scrutinize specifically the Diels-Alder reaction. Its 3D nature and the lack of a singular directionality of charge movement upon barrier crossing make the effect of the elec. field not obvious. We show that the elec. field topol. around the dienophile double bond and the assocd. changes in the topol. of the electron d. in this bond are predictors of the reaction barrier. They are also the metrics to rationalize and predict how the external field would inhibit or enhance the reaction. The findings pave the way toward designing external fields for catalysis and reading the reactivity without an explicit mechanistic interrogation, for a variety of reactions.
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    (m) Martin, D. J.; Mayer, J. M. Oriented Electrostatic Effects on O2 and CO2 Reduction by a Polycationic Iron Porphyrin. J. Am. Chem. Soc. 2021, 143, 11423– 11434,  DOI: 10.1021/jacs.1c03132
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    9m
    Oriented Electrostatic Effects on O2 and CO2 Reduction by a Polycationic Iron Porphyrin
    Martin, Daniel J.; Mayer, James M.
    Journal of the American Chemical Society (2021), 143 (30), 11423-11434CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Next-generation energy technologies require improved methods for rapid and efficient chem.-to-elec. energy transformations. One new approach has been to include atomically positioned, electrostatic motifs in mol. catalysts to stabilize high-energy, charged intermediates. For example, an iron porphyrin bearing four cationic, o-N,N,N-trimethylanilinium groups (o-[N(CH3)3]+) has recently been used to catalyze the complex, multistep O2 and CO2 redn. reactions (ORR and CO2RR) with fast rates and at low overpotentials. The success of this catalyst is attributed, at least in part, to specific charge-charge interactions between the atomically positioned o-[N(CH3)3]+ groups and the bound substrate. However, by nature of the mono-ortho substitution pattern, there are four possible atropisomers of this metalloporphyrin and thus four unique electrostatic environments. This work reports that each of the four individual atropisomers catalyzes both the ORR and CO2RR with fast rates and low overpotentials. The max. turnover frequencies vary among the atropisomers, by a factor of 60 for the ORR and a factor of 5 for CO2RR. For the ORR, the αβαβ isomer is the fastest and has the highest overpotential, while for the CO2RR the αααα isomer is the fastest and has the highest overpotential. The role of charge positioning is complex and can affect more than a single step such as CO2 binding. These data offer a first-of-a-kind perspective on atomically positioned charge and highlight the significance of high charge d., rather than orientation, on the thermodn. and kinetics of multistep mol. electrochem. transformations.
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    (n) Mejía, L.; Garay-Ruiz, D.; Franco, I. Diels–Alder Reaction in a Molecular Junction. J. Phys. Chem. C 2021, 125, 14599– 14606,  DOI: 10.1021/acs.jpcc.1c01901
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    9n
    Diels-Alder Reaction in a Molecular Junction
    Mejia, Leopoldo; Garay-Ruiz, Diego; Franco, Ignacio
    Journal of Physical Chemistry C (2021), 125 (27), 14599-14606CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    We computationally investigate the utility of mol. junctions to probe chem. reactivity at the single-mol. limit. To do so, we employ mol. dynamics (MD) coupled to quantum transport simulations to investigate the classic Diels-Alder reaction but in the context of nanoscale junctions where the reactants are nanoconfined and the reactive pair is mech. brought to proximity. To capture reactive events, the MD employs the d. functional tight binding method to account for interat. interactions. To understand the thermodn. driving forces behind the reaction in this novel chem. environment, we reconstruct the potential of mean force along the reaction coordinate and decomp. it into energetic and entropic contributions. The anal. demonstrates that the process is entropically penalized, which makes the reaction barrier sensitive to changes in the temp. and reactant rigidity. The simulations further show that in nanojunctions the degree of reactivity can be mech. manipulated simply by controlling the proximity of the electrodes. Surprisingly, for optimal electrode sepns., the entropic and energetic cost in the nanoconfined reaction coincides with that obsd. in bulk, establishing a clear connection between measurements performed in these two vastly different reactive environments. Finally, we show how conductance measurements can be used to exptl. monitor the process at the single-entity limit.
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    (o) Wang, W.-W.; Shang, F.-L.; Zhao, X. Switchable (2 + 2) and (4 + 2) Cycloadditions on Boron Nitride Nanotubes under Oriented External Electric Fields: A Mechanistic Study. J. Org. Chem. 2021, 86, 3785– 3791,  DOI: 10.1021/acs.joc.0c02590
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    9o
    Switchable (2 + 2) and (4 + 2) Cycloadditions on Boron Nitride Nanotubes under Oriented External Electric Fields: A Mechanistic Study
    Wang, Wei-Wei; Shang, Fu-Lin; Zhao, Xiang
    Journal of Organic Chemistry (2021), 86 (5), 3785-3791CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)
    The (2 + 2) and (4 + 2) cycloaddns. are important approaches for the functional derivatizations of nanocarbon and hexagonal boron nitride (hBN) materials. However, as two competing reactions with similar reactivity, it is difficult to control the type of reactions and the corresponding adducts in practice. Here, we introduced a mechanistic study of the oriented external elec. field (OEEF)-modulated cycloaddns. of pristine and substituted benzynes on the zigzag boron nitride nanotubes. Owing to the distinct charge transfer directions between the competing (2 + 2) and (4 + 2) reactions and the resultant distinct responses of the barriers to the fields along the tube axis, we found that OEEF plays opposing catalytic roles in these two types of reactions and the effect of elec. field as a catalyst or inhibitor can be easily reversed by flipping the field vector to achieve selective reactions and products at will.
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  10. 10
    (a) Ciampi, S.; Darwish, N.; Aitken, H. M.; Díez-Pérez, I.; Coote, M. L. Harnessing Electrostatic Catalysis in Single Molecule, Electrochemical and Chemical Systems: a Rapidly Growing Experimental Tool Box. Chem. Soc. Rev. 2018, 47, 5146– 5164,  DOI: 10.1039/C8CS00352A
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    10a
    Harnessing electrostatic catalysis in single molecule, electrochemical and chemical systems: a rapidly growing experimental tool box
    Ciampi, Simone; Darwish, Nadim; Aitken, Heather M.; Diez-Perez, Ismael; Coote, Michelle L.
    Chemical Society Reviews (2018), 47 (14), 5146-5164CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
    Static electricity is central to many day-to-day practical technologies, from sepn. methods in the recycling of plastics to transfer inks in photocopying, but the exploration of how electrostatics affects chem. bonding is still in its infancy. As shown in the Companion Tutorial, the presence of an appropriately-oriented elec. field can enhance the resonance stabilization of transition states by lowering the energy of ionic contributors, and the effect that follows on reaction barriers can be dramatic. However, the electrostatic effects are strongly directional and harnessing them in practical expts. has proven elusive until recently. This tutorial outlines some of the exptl. platforms through which we have sought to translate abstr. theor. concepts of electrostatic catalysis into practical chem. technologies. We move step-wise from the nano to the macro, using recent examples drawn from single-mol. STM expts., surface chem. and pH-switches in soln. chem. The expts. discussed in the tutorial will educate the reader in some of the viable solns. to gain control of the orientation of reagents in that field; from pH-switchable bond-dissocns. using charged functional groups to the use of surface chem. and surface-probe techniques. All of these recent works provide proof-of-concept of electrostatic catalysis for specific sets of chem. reactions. They overturn the long-held assumption that static electricity can only affect rates and equil. position of redox reactions, but most importantly, they provide glimpses of the wide-ranging potential of external elec. fields for controlling chem. reactivity and selectivity.
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    (b) Simpson, G. J.; García-López, V.; Daniel Boese, A.; Tour, J. M.; Grill, L. How to control single-molecule rotation. Nat. Commun. 2019, 10, 4631  DOI: 10.1038/s41467-019-12605-8
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    10b
    How to control single-molecule rotation
    Simpson Grant J; Grill Leonhard; Garcia-Lopez Victor; Tour James M; Daniel Boese A
    Nature communications (2019), 10 (1), 4631 ISSN:.
    The orientation of molecules is crucial in many chemical processes. Here, we report how single dipolar molecules can be oriented with maximum precision using the electric field of a scanning tunneling microscope. Rotation is found to occur around a fixed pivot point that is caused by the specific interaction of an oxygen atom in the molecule with the Ag(111) surface. Both directions of rotation are realized at will with 100% directionality. Consequently, the internal dipole moment of an individual molecule can be spatially mapped via its behavior in an applied electric field. The importance of the oxygen-surface interaction is demonstrated by the addition of a silver atom between a single molecule and the surface and the consequent loss of the pivot point.
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  11. 11
    Bandrauk, A. D.; Sedik, E.-W. S.; Matta, C. F. Effect of Absolute Laser Phase on Reaction Paths in Laser-Induced Chemical Reactions. J. Chem. Phys. 2004, 121, 7764– 7775,  DOI: 10.1063/1.1793931
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    11
    Effect of absolute laser phase on reaction paths in laser-induced chemical reactions
    Bandrauk, Andre D.; Sedik, El-Wallid S.; Matta, Cherif F.
    Journal of Chemical Physics (2004), 121 (16), 7764-7775CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    Potential surfaces, dipole moments, and polarizabilities are calcd. by ab initio methods [unrestricted MP2(full)/6-311++G(2d,2p)] along the reaction paths of the F + CH4 and Cl + CH4 reaction systems. It is found that in general dipole moments and polarizabilities exhibit peaks near the transition state. In the case of X = F these peaks are on the products side and in the case of X = Cl they are on the reactants side indicating an early transition state in the case of fluorine and a late transition state in the case of chlorine. An anal. of the geometric changes along the reaction paths reveals a one-to-one correspondence between the peaks in the elec. properties and peaks in the rate of change of certain internal geometric coordinates along the reaction path. Interaction with short IR intense laser fields pulses leads to the possibility of interferences between the dipole and polarizability laser-mol. interactions as a function of laser phase. The larger dipole moment in the Cl + CH4 reaction can lead to the creation of deep wells (instead of energy barriers) and new strongly bound states in the transition state region. This suggests possible coherent control of the reaction path as a function of the abs. phase of the incident field, by significant modification of the potential surfaces along the reaction path and, in particular, in the transition state region.
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  12. 12
    Climent, C.; Galego, J.; Garcia-Vidal, F. J.; Feist, J. Plasmonic Nanocavities Enable Self-Induced Electrostatic Catalysis. Angew. Chem., Int. Ed. 2019, 58, 8698– 8702,  DOI: 10.1002/anie.201901926
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    12
    Plasmonic Nanocavities Enable Self-Induced Electrostatic Catalysis
    Climent, Claudia; Galego, Javier; Garcia-Vidal, Francisco J.; Feist, Johannes
    Angewandte Chemie, International Edition (2019), 58 (26), 8698-8702CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The potential of strong interactions between light and matter remains to be further explored within a chem. context. Towards this end herein the authors study the electromagnetic interaction between mols. and plasmonic nanocavities. By electronic structure calcns., self-induced catalysis emerges without any external stimuli through the interaction of the mol. permanent and fluctuating dipole moments with the plasmonic cavity modes. This scheme was exploited to modify the transition temp. T1/2 of spin-crossover complexes as an example of how strong light-matter interactions can ultimately be used to control a materials responses.
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  13. 13
    (a) Li, A.; Zi, Y.; Guo, H.; Wang, Z. L.; Fernández, F. M. Triboelectric Nanogenerators for Sensitive Nano-Coulomb Molecular Mass Spectrometry. Nat. Nanotechnol. 2017, 12, 481– 487,  DOI: 10.1038/nnano.2017.17
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    13a
    Triboelectric nanogenerators for sensitive nano-coulomb molecular mass spectrometry
    Li, Anyin; Zi, Yunlong; Guo, Hengyu; Wang, Zhong Lin; Fernandez, Facundo M.
    Nature Nanotechnology (2017), 12 (5), 481-487CODEN: NNAABX; ISSN:1748-3387. (Nature Publishing Group)
    Ion sources for mol. mass spectrometry are usually driven by d.c. power supplies with no user control over the total charges generated. Here, we show that the output of triboelec. nanogenerators (TENGs) can quant. control the total ionization charges in mass spectrometry. The high output voltage of TENGs can generate single- or alternating-polarity ion pulses, and is ideal for inducing nanoelectrospray ionization (nanoESI) and plasma discharge ionization. For a given nanoESI emitter, accurately controlled ion pulses ranging from 1.0 to 5.5 nC were delivered with an onset charge of 1.0 nC. Spray pulses can be generated at a high frequency of 17 Hz (60 ms in period) and the pulse duration is adjustable on-demand between 60 ms and 5.5 s. Highly sensitive (∼0.6 zeptomole) mass spectrometry anal. using minimal sample (18 pl per pulse) was achieved with a 10 pg ml-1 cocaine sample. We also show that native protein conformation is conserved in TENG-ESI, and that patterned ion deposition on conductive and insulating surfaces is possible.
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    (b) Xia, H.; Wang, Z. Piezoelectricity Drives Organic Synthesis. Science 2019, 366, 1451– 1452,  DOI: 10.1126/science.aaz9758
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    13b
    Piezoelectricity drives organic synthesis
    Xia, Hesheng; Wang, Zhenhua
    Science (Washington, DC, United States) (2019), 366 (6472), 1451-1452CODEN: SCIEAS; ISSN:1095-9203. (American Association for the Advancement of Science)
    The coupling of mech. and chem. phenomena on a mol. scale, mechanochem., is undergoing an exciting period of rediscovery and renaissance (). Mechanochem. research can provide deep insight into the rupture mechanism of chem. bonds (). Mechanochem. routes for chem. synthesis can minimize the use of hazardous or undesirable solvents. They also can generate materials along reaction pathways that are inaccessible through thermal or light-activated processes. On page 1500 of this issue, Kubota et al. demonstrate that piezoelec. materials can be used as mechanoredox catalysts for org. synthesis ().
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    (c) Zhang, J.; Ciampi, S. Shape and Charge: Faraday’s Ice Pail Experiment Revisited. ACS Cent. Sci. 2020, 6, 611– 612,  DOI: 10.1021/acscentsci.0c00298
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    13c
    Shape and Charge: Faraday's Ice Pail Experiment Revisited
    Zhang, Jinyang; Ciampi, Simone
    ACS Central Science (2020), 6 (5), 611-612CODEN: ACSCII; ISSN:2374-7951. (American Chemical Society)
    A review. Faraday pail measurements of charged dielecs. are not as straightforward as previously thought.
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  14. 14
    Grahame, D. C. The Electrical Double Layer and the Theory of Electrocapillarity. Chem. Rev. 1947, 41, 441– 501,  DOI: 10.1021/cr60130a002
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    14
    The electrical double layer and the theory of electro-capillarity
    Grahame, David C.
    Chemical Reviews (Washington, DC, United States) (1947), 41 (), 441-501CODEN: CHREAY; ISSN:0009-2665.
    A review with 95 references.
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  15. 15
    Heo, J.; Ahn, H.; Won, J.; Son, J. G.; Shon, H. K.; Lee, T. G.; Han, S. W.; Baik, M. H. Electro-inductive effect: Electrodes as functional groups with tunable electronic properties. Science 2020, 370, 214– 219,  DOI: 10.1126/science.abb6375
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    15
    Electro-inductive effect: Electrodes as functional groups with tunable electronic properties
    Heo, Joon; Ahn, Hojin; Won, Joonghee; Son, Jin Gyeong; Shon, Hyun Kyong; Lee, Tae Geol; Han, Sang Woo; Baik, Mu-Hyun
    Science (Washington, DC, United States) (2020), 370 (6513), 214-219CODEN: SCIEAS; ISSN:1095-9203. (American Association for the Advancement of Science)
    In place of functional groups that impose different inductive effects, we immobilize mols. carrying thiol groups on a gold electrode. By applying different voltages, the properties of the immobilized mols. can be tuned. The base-catalyzed sapon. of benzoic esters is fully inhibited by applying a mildly neg. voltage of -0.25 V vs. open circuit potential. Furthermore, the rate of a Suzuki-Miyaura cross-coupling reaction can be changed by applying a voltage when the arylhalide substrate is immobilized on a gold electrode. Finally, a two-step carboxylic acid amidation is shown to benefit from a switch in applied voltage between addn. of a carbodiimide coupling reagent and introduction of the amine.
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  16. 16
    Patrow, J. G.; Sorenson, S. A.; Dawlaty, J. M. Direct Spectroscopic Measurement of Interfacial Electric Fields near an Electrode under Polarizing or Current-Carrying Conditions. J. Phys. Chem. C 2017, 121, 11585– 11592,  DOI: 10.1021/acs.jpcc.7b03134
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    16
    Direct Spectroscopic Measurement of Interfacial Electric Fields near an Electrode under Polarizing or Current-Carrying Conditions
    Patrow, Joel G.; Sorenson, Shayne A.; Dawlaty, Jahan M.
    Journal of Physical Chemistry C (2017), 121 (21), 11585-11592CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    Interfacial elec. fields and the related mol. polarization are the central quantities that govern charge transfer between an electrode and a mol. The presence of the interfacial field is often inferred indirectly through transport and capacitance measurements. It is desirable to measure such fields directly via the Stark shift that they induce on mol. vibrations. We report the Stark shift of a well-known vibrational chromophore tethered near an electrochem. interface measured using vibrational sum frequency generation spectroscopy. We have two important findings. First, we observe that the measured local field scales with respect to the ionic concn. in the electrolyte according to a model that combines the Gouy-Chapman theory with the capacitive response of a mol. layer. This behavior holds over 3 orders of magnitude in ionic concn., therefore lending support to the validity of the model. Our results along with this model allow for estn. of the elec. field near the electrode as the potential and ionic concn. are varied. Second, we observe that the mentioned variation of the local field with changing potential only occurs for pos. potentials, for which the electrode is polarized but negligible current flows. For neg. potentials, a sustained electrochem. current is obsd. that likely arises due to electron transfer and subsequent redn. of protons in the electrolyte. Interestingly, we observe that, under this condition, the local field does not vary with increasingly neg. applied potential, reminiscent of the field within a leaky capacitor. The important consequence of this observation is that an increase in the thermodn. drive for an electrochem. reaction does not necessarily translate to increased mol. polarization near the surface when a sustained current is passing. This study will serve as a baseline in all areas of chem. in which understanding the role of local fields near interfaces is important and will provide a new perspective for interfacial charge transfer theories.
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  17. 17
    (a) Ge, A.; Videla, P. E.; Lee, G. L.; Rudshteyn, B.; Song, J.; Kubiak, C. P.; Batista, V. S.; Lian, T. Interfacial Structure and Electric Field Probed by in Situ Electrochemical Vibrational Stark Effect Spectroscopy and Computational Modeling. J. Phys. Chem. C 2017, 121, 18674– 18682,  DOI: 10.1021/acs.jpcc.7b05563
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    17a
    Interfacial Structure and Electric Field Probed by in Situ Electrochemical Vibrational Stark Effect Spectroscopy and Computational Modeling
    Ge, Aimin; Videla, Pablo E.; Lee, Gwendolynne L.; Rudshteyn, Benjamin; Song, Jia; Kubiak, Clifford P.; Batista, Victor S.; Lian, Tianquan
    Journal of Physical Chemistry C (2017), 121 (34), 18674-18682CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    Interfacial elec. fields play crucial roles in electrochem., catalysis, and solar energy conversion. Understanding of the interfacial elec. field effects was hindered by the lack of a direct spectroscopic method to probe of the interfacial field at the mol. level. Here, the authors report the characterization of the field and interfacial structure at Au/diisocyanide/aq. electrolyte interfaces, using a combination of in situ electrochem. vibrational sum frequency generation (SFG) spectroscopy, d. functional theory (DFT) calcns., and mol. dynamics (MD) simulations. For 1,4-phenylene diisocyanide (PDI), 4,4'-biphenyl diisocyanide (BPDI), and 4,4''-p-terphenyl diisocyanide (TPDI), the authors' results reveal that the frequency of the Au-bound NC stretch mode of the diisocyanide self-assembled monolayer (SAM) increases linearly with the applied potential, suggesting that SFG can be an in situ probe of the strength of the elec. field at electrode/electrolyte interfaces. Using DFT-computed Stark tuning rates of model complexes, the elec. field strength at the metal/SAM/electrolyte interfaces is 108-109 V/m. The linear dependence of the vibrational frequency (and field) with applied potential is consistent with an electrochem. double-layer structure that consists of a Helmholtz layer in contact with a diffused layer. The Helmholtz layer thickness is approx. the same as the mol. length for PDI, suggesting a well-ordered SAM with negligible electrolyte penetration. For BPDI and TPDI, the Helmholtz layer is thinner than the monolayer of mol. adsorbates, indicating that the electrolyte percolates into the SAM, as shown by mol. dynamics simulations of the Au/PDI/electrolyte interface. The reported anal. demonstrates that a combination of in situ SFG probes and computational modeling provides a powerful approach to elucidate the structure of electrochem. interfaces at the detailed mol. level.
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    (b) Clark, M. L.; Ge, A.; Videla, P. E.; Rudshteyn, B.; Miller, C. J.; Song, J.; Batista, V. S.; Lian, T.; Kubiak, C. P. CO2 Reduction Catalysts on Gold Electrode Surfaces Influenced by Large Electric Fields. J. Am. Chem. Soc. 2018, 140, 17643– 17655,  DOI: 10.1021/jacs.8b09852
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    17b
    CO2 Reduction Catalysts on Gold Electrode Surfaces Influenced by Large Electric Fields
    Clark, Melissa L.; Ge, Aimin; Videla, Pablo E.; Rudshteyn, Benjamin; Miller, Christopher J.; Song, Jia; Batista, Victor S.; Lian, Tianquan; Kubiak, Clifford P.
    Journal of the American Chemical Society (2018), 140 (50), 17643-17655CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Attaching mol. catalysts to metal and semiconductor electrodes is a promising approach to developing new catalytic electrodes with combined advantages of mol. and heterogeneous catalysts. However, the effect of the interfacial elec. field on the stability, activity, and selectivity of the catalysts is often poorly understood due to the complexity of interfaces. The authors examine the strength of the interfacial field at the binding site of CO2 redn. catalysts including Re(S-2,2'-bipyridine)(CO)3Cl and Mn(S-2,2'-bipyridine)(CO)3Br immobilized on Au electrodes. The vibrational spectra are probed by sum frequency generation spectroscopy (SFG), showing pronounced potential-dependent frequency shifts of the carbonyl stretching modes. Calcns. of SFG spectra and Stark tuning rates based on d. functional theory allow for direct interpretation of the configurations of the catalysts bound to the surfaces and the influence of the interfacial elec. field. Electrocatalysts supported on Au electrodes have tilt angles of ∼65-75° relative to the surface normal with one of the carbonyl ligands in direct contact with the surface. Large interfacial elec. fields of 108-109 V/m are detd. through the anal. of exptl. frequency shifts and theor. Stark tuning rates of the sym. CO stretching mode. These large elec. fields thus significantly influence the CO2 binding site.
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    (c) Ge, A.; Rudshteyn, B.; Videla, P. E.; Miller, C. J.; Kubiak, C. P.; Batista, V. S.; Lian, T. Heterogenized Molecular Catalysts: Vibrational Sum-Frequency Spectroscopic, Electrochemical, and Theoretical Investigations. Acc. Chem. Res. 2019, 52, 1289– 1300,  DOI: 10.1021/acs.accounts.9b00001
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    17c
    Heterogenized Molecular Catalysts: Vibrational Sum-Frequency Spectroscopic, Electrochemical, and Theoretical Investigations
    Ge, Aimin; Rudshteyn, Benjamin; Videla, Pablo E.; Miller, Christopher J.; Kubiak, Clifford P.; Batista, Victor S.; Lian, Tianquan
    Accounts of Chemical Research (2019), 52 (5), 1289-1300CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
    A review. Rhenium and manganese bipyridyl tricarbonyl complexes have attracted intense interest for their promising applications in photocatalytic and electrocatalytic CO2 redn. in both homogeneous and heterogenized systems. To date, there have been extensive studies on immobilizing Re catalysts on solid surfaces for higher catalytic efficiency, reduced catalyst loading, and convenient product sepn. However, in order for the heterogenized mol. catalysts to achieve the combination of the best aspects of homogeneous and heterogeneous catalysts, it is essential to understand the fundamental physicochem. properties of such heterogeneous systems, such as surface-bound structures of Re/Mn catalysts, substrate-adsorbate interactions, and photoinduced or elec.-field-induced effects on Re/Mn catalysts. For example, the surface may act to (un)block substrates, (un)trap charges, (de)stabilize particular intermediates (and thus affect scaling relations), and shift potentials in different directions, just as protein environments do. The close collaboration between the Lian, Batista, and Kubiak groups has resulted in an integrated approach to investigate how the semiconductor or metal surface affects the properties of the attached catalyst. Synthetic strategies to achieve stable and controlled attachment of Re/Mn mol. catalysts have been developed. Steady-state, time-resolved, and electrochem. vibrational sum-frequency generation (SFG) spectroscopic studies have provided insight into the effects of interfacial structures, ultrafast vibrational energy relaxation, and elec. field on the Re/Mn catalysts, resp. Various computational methods utilizing d. functional theory (DFT) have been developed and applied to det. the mol. orientation by direct comparison to spectroscopy, unravel vibrational energy relaxation mechanisms, and quantify the interfacial elec. field strength of the Re/Mn catalyst systems.This Account starts with a discussion of the recent progress in detg. the surface-bound structures of Re catalysts on semiconductor and Au surfaces by a combined vibrational SFG and DFT study. The effects of crystal facet, length of anchoring ligands, and doping of the semiconductor on the bound structures of Re catalysts and of the substrate itself are discussed. This is followed by a summary of the progress in understanding the vibrational relaxation (VR) dynamics of Re catalysts covalently adsorbed on semiconductor and metal surfaces. The VR processes of Re catalysts on TiO2 films and TiO2 single crystals and a Re catalyst tethered on Au, particularly the role of electron-hole pair (EHP)-induced coupling on the VR of the Re catalyst bound on Au, are discussed. The Account also summarizes recent studies in quantifying the elec. field strength experienced by the catalytically active site of the Re/Mn catalyst bound on a Au electrode based on a combined electrochem. SFG and DFT study of the Stark tuning of the CO stretching modes of these catalysts. Finally, future research directions on surface-immobilized mol. catalyst systems are discussed.
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  18. 18
    (a) Fried, S. D.; Boxer, S. G. Electric Fields and Enzyme Catalysis. Annu. Rev. Biochem. 2017, 86, 387– 415,  DOI: 10.1146/annurev-biochem-061516-044432
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    18a
    Electric Fields and Enzyme Catalysis
    Fried, Stephen D.; Boxer, Steven G.
    Annual Review of Biochemistry (2017), 86 (), 387-415CODEN: ARBOAW; ISSN:0066-4154. (Annual Reviews)
    A review. What happens inside an enzyme's active site to allow slow and difficult chem. reactions to occur so rapidly. This question has occupied biochemists' attention for a long time. Computer models of increasing sophistication have predicted an important role for electrostatic interactions in enzymic reactions, yet this hypothesis has proved vexingly difficult to test exptl. Recent expts. utilizing the vibrational Stark effect make it possible to measure the elec. field a substrate mol. experiences when bound inside its enzyme's active site. These expts. have provided compelling evidence supporting a major electrostatic contribution to enzymic catalysis. Here, we review these results and develop a simple model for electrostatic catalysis that enables us to incorporate disparate concepts introduced by many investigators to describe how enzymes work into a more unified framework stressing the importance of elec. fields at the active site.
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    (b) Vaissier Welborn, V.; Head-Gordon, T. Computational Design of Synthetic Enzymes. Chem. Rev. 2019, 119, 6613– 6630,  DOI: 10.1021/acs.chemrev.8b00399
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    18b
    Computational Design of Synthetic Enzymes
    Vaissier Welborn, Valerie; Head-Gordon, Teresa
    Chemical Reviews (Washington, DC, United States) (2019), 119 (11), 6613-6630CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review. We review the std. model for de novo computational design of enzymes, which primarily focuses on the development of an active site geometry, composed of protein functional groups in orientations optimized to stabilize the transition state, for a novel chem. reaction not found in nature. Its emphasis is placed on the structure and energetics of the active site embedded in an accommodating protein that serves as a phys. support that shields the reaction chem. from solvent, which is typically improved upon using lab. directed evolution. We also provide a review of design strategies that move beyond the std. model, by placing more emphasis on the designed enzyme as a whole catalytic construct. Starting with complete de novo enzyme design examples, we consider addnl. design factors such as entropy of individual residues, correlated motion between side chains (mutual information), dynamical correlations of the enzyme motions that could aid the reaction, reorganization energy, and elec. fields as a way to exploit the entire protein scaffold to improve upon the catalytic rate, thereby providing directed evolution with better starting sequences for increasing the biocatalytic performance.
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    (c) Bím, D.; Alexandrova, A. N. Electrostatic Regulation of Blue Copper Sites. Chem. Sci. 2021, 12, 11406– 11413,  DOI: 10.1039/D1SC02233D
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    18c
    Electrostatic regulation of blue copper sites
    Bim, Daniel; Alexandrova, Anastassia N.
    Chemical Science (2021), 12 (34), 11406-11413CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
    In the last 50 years, the blue copper proteins became central targets of investigation. Extensive expts. focused on the Cu coordination to probe the effect of local perturbations on its properties. We found that local elec. fields, generated by charged residues evolutionarily placed throughout the protein edifice, mainly second sphere, but also more remotely, constitute an addnl. significant factor regulating blue copper proteins. These fields are not random, but exhibit a highly specific directionality, neg. with respect to the .vector.(Cu - SCys) and .vector.(Cu - SMet) vectors in the Cu first shell. The field magnitude contributes to fine-tuning of the geometric and electronic properties of Cu sites in individual blue copper proteins. Specifically, the local elec. fields evidently control the Cu-SMet bond distance, Cu(II)-SCys bond covalency, and the energies of the frontier MOs, which, in turn, govern the Cu(II/I) redn. potential and the relative absorption intensities at 450 nm and 600 nm.
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  19. 19
    (a) Shaik, S.; de Visser, S. P.; Kumar, D. External Electric Field Will Control the Selectivity of Enzymatic-Like Bond Activations. J. Am. Chem. Soc. 2004, 126, 11746– 11749,  DOI: 10.1021/ja047432k
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    19a
    External Electric Field Will Control the Selectivity of Enzymatic-Like Bond Activations
    Shaik, Sason; de Visser, Sam P.; Kumar, Devesh
    Journal of the American Chemical Society (2004), 126 (37), 11746-11749CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Controlling the selectivity of a chem. reaction is a Holy Grail in chem. This paper reports theor. results of unprecedented effects induced by moderately strong elec. fields on the selectivity of two competing nonpolar bond activation processes, C-H hydroxylation vs. C:C epoxidn., promoted by an active species that is common to heme-enzymes and to metallo-org. catalysts. The mol. system by itself shows no selectivity whatsoever. However, the presence of an elec. field induces abs. selectivity that can be controlled at will. Thus, the choice of the orientation and direction of the field vis-a-vis the mol. axes drives the reaction in the direction of complete C-H hydroxylation or complete C:C epoxidn.
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    (b) Schyman, P.; Lai, W.; Chen, H.; Wang, Y.; Shaik, S. The Directive of the Protein: How Does Cytochrome P450 Select the Mechanism of Dopamine Formation?. J. Am. Chem. Soc. 2011, 133, 7977– 7984,  DOI: 10.1021/ja201665x
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    19b
    The Directive of the Protein: How Does Cytochrome P450 Select the Mechanism of Dopamine Formation?
    Schyman, Patric; Lai, Wenzhen; Chen, Hui; Wang, Yong; Shaik, Sason
    Journal of the American Chemical Society (2011), 133 (20), 7977-7984CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Dopamine can be generated from tyramine via arene hydroxylation catalyzed by a cytochrome P 450 enzyme (CYP2D6). Our quantum mech./mol. mech. (QM/MM) results reveal the decisive impact of the protein in selecting the best' reaction mechanism. Instead of the traditional Meisenheimer-complex mechanism, the study reveals a mechanism involving an initial hydrogen atom transfer from the phenolic hydroxyl group of the tyramine to the iron-oxo of the compd. I (Cpd I), followed by a ring-π radical rebound that eventually leads to dopamine by keto-enol rearrangement. This mechanism is not viable in the gas phase since the O-H bond activation by Cpd I is endothermic and the process does not form a stable intermediate. By contrast, the in-protein reaction has a low barrier and is exothermic. It is shown that the local elec. field of the protein environment serves as a template that stabilizes the intermediate of the H-abstraction step and thereby mediates the catalysis of dopamine formation at a lower energy cost. Furthermore, it is shown that external elec. fields can either catalyze or inhibit the process depending on their directionality.
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    (c) Stuyver, T.; Ramanan, R.; Mallick, D.; Shaik, S. Oriented (Local) Electric Fields Drive the Millionfold Enhancement of the H-Abstraction Catalysis Observed for Synthetic Metalloenzyme Analogues. Angew. Chem., Int. Ed. 2020, 59, 7915– 7920,  DOI: 10.1002/anie.201916592
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    19c
    Oriented (Local) Electric Fields Drive the Millionfold Enhancement of the H-Abstraction Catalysis Observed for Synthetic Metalloenzyme Analogues
    Stuyver, Thijs; Ramanan, Rajeev; Mallick, Dibyendu; Shaik, Sason
    Angewandte Chemie, International Edition (2020), 59 (20), 7915-7920CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    This contribution follows the recent remarkable catalysis obsd. by Groves et al. in hydrogen-abstraction reactions by (a) an oxoferryl porphyrin radical-cation complex [Por.++FeIV(O)Lax] and (b) a hydroxoiron porphyrazine ferric complex [PyPzFeIII(OH)Lax], both of which involve pos. charged substituents on the outer circumference of the resp. macrocyclic ligands. These charge-coronated complexes are analogs of the biol. important Compd. I (Cpd I) and synthetic hydroxoferric species, resp. We demonstrate that the obsd. enhancement of the H-abstraction catalysis for these systems is a purely electrostatic effect, elicited by the local charges embedded on the peripheries of the resp. macrocyclic ligands. Our findings provide new insights into how electrostatics can be employed to tune the catalytic activity of metalloenzymes and can thus contribute to the future design of new and highly efficient hydrogen-abstraction catalysts.
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    (d) Bím, D.; Alexandrova, A. N. Local Electric Fields As a Natural Switch of Heme-Iron Protein Reactivity. ACS Catal. 2021, 11, 6534– 6546,  DOI: 10.1021/acscatal.1c00687
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    19d
    Local Electric Fields As a Natural Switch of Heme-Iron Protein Reactivity
    Bim, Daniel; Alexandrova, Anastassia N.
    ACS Catalysis (2021), 11 (11), 6534-6546CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
    Heme-iron oxidoreductases operating through the high-valent FeIVO intermediates perform crucial and complicated transformations, such as oxidns. of unreactive satd. hydrocarbons. These enzymes share the same Fe coordination, only differing by the axial ligation, e.g., Cys in P 450 oxygenases, Tyr in catalases, and His in peroxidases. By examg. ~ 200 heme-iron proteins, the protein hosts exert highly specific intramol. elec. fields on the active sites, and there is a strong correlation between the direction and magnitude of this field and the protein function. In all heme proteins, the field is preferentially aligned with the Fe-O bond (Fz). The Cys-ligated P 450 oxygenases have the highest av. Fz of 28.5 MV cm-1, i.e., most enhancing the oxyl-radical character of the oxo group, and consistent with the ability of these proteins to activate strong C-H bonds. In contrast, in Tyr-ligated proteins, the av. Fz is only 3.0 MV cm-1, apparently suppressing single-electron off-pathway oxidns., and in His-ligated proteins, Fz is -8.7 MV cm-1. The operational field range is given by the trade-off between the low reactivity of the FeIVO compd. I at the more neg. Fz and the low selectivity at the more pos. Fz. Consequently, a heme-iron site placed in the field characteristic of another heme-iron protein class loses its canonical function and gains an adverse one. Thus, elec. fields produced by the protein scaffolds, together with the nature of the axial ligand, control all heme-iron chem.
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    (e) Ramanan, R.; Waheed, S. O.; Schofield, C. J.; Christov, C. Z. What Is the Catalytic Mechanism of Enzymatic Histone N-Methyl Arginine Demethylation and Can It Be Influenced by an External Electric Field?. Chem.─Eur. J. 2021, 27, 11827– 11836,  DOI: 10.1002/chem.202101174
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    19e
    What is the Catalytic Mechanism of Enzymatic Histone N-Methyl Arginine Demethylation and Can It be Influenced by an External Electric Field?
    Ramanan, Rajeev; Waheed, Sodiq O.; Schofield, Christopher J.; Christov, Christo Z.
    Chemistry - A European Journal (2021), 27 (46), 11827-11836CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Arginine methylation is an important mechanism of epigenetic regulation. Some Fe(II) and 2-oxoglutarate dependent Jumonji-C (JmjC) Nε-Me lysine histone demethylases also have N-Me arginine demethylase activity. We report combined mol. dynamic (MD) and Quantum Mech./Mol. Mech. (QM/MM) studies on the mechanism of N-Me arginine demethylation by human KDM4E and compare the results with those reported for N-Me lysine demethylation by KDM4A. At the KDM4E active site, Glu191, Asn291, and Ser197 form a conserved scaffold that restricts substrate dynamics; substrate binding is also mediated by an out of active site hydrogen-bond between the substrate Ser1 and Tyr178. The calcns. imply that in either C-H or N-H potential bond cleaving pathways for hydrogen atom transfer (HAT) during N-Me arginine demethylation, electron transfer occurs via a σ-channel; the transition state for the N-H pathway is ∼10 kcal/mol higher than for the C-H pathway due to the higher bond dissocn. energy of the N-H bond. The results of applying external elec. fields (EEFs) reveal EEFs with pos. field strengths parallel to the Fe=O bond have a significant barrier-lowering effect on the C-H pathway, by contrast, such EEFs inhibit the N-H activation rate. The overall results imply that KDM4 catalyzed N-Me arginine demethylation and N-Me lysine demethylation occur via similar C-H abstraction and rebound mechanisms leading to Me group hydroxylation, though there are differences in the interactions leading to productive binding of intermediates.
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  20. 20
    Li, W.-L.; Head-Gordon, T. Catalytic Principles from Natural Enzymes and Translational Design Strategies for Synthetic Catalysts. ACS Cent. Sci. 2021, 7, 72– 80,  DOI: 10.1021/acscentsci.0c01556
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    20
    Catalytic Principles from Natural Enzymes and Translational Design Strategies for Synthetic Catalysts
    Li, Wan-Lu; Head-Gordon, Teresa
    ACS Central Science (2021), 7 (1), 72-80CODEN: ACSCII; ISSN:2374-7951. (American Chemical Society)
    A review. As biocatalysts, enzymes are characterized by their high catalytic efficiency and strong specificity but are relatively fragile by requiring narrow and specific reactive conditions for activity. Synthetic catalysts offer an opportunity for more chem. versatility operating over a wider range of conditions but currently do not reach the remarkable performance of natural enzymes. Here we consider some new design strategies based on the contributions of nonlocal elec. fields and thermodn. fluctuations to both improve the catalytic step and turnover for rate acceleration in arbitrary synthetic catalysts through bioinspired studies of natural enzymes. With a focus on the enzyme as a whole catalytic construct, we illustrate the translational impact of natural enzyme principles to synthetic enzymes, supramol. capsules, and electrocatalytic surfaces. Designed strategies based on elec. fields and thermodn. fluctuations are considered to improve the catalytic step and turnover in synthetic catalysts through bioinspired studies of natural enzymes.
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  21. 21
    Liu, C. T.; Layfield, J. P.; Stewart, R. J.; French, J. B.; Hanoian, P.; Asbury, J. B.; Hammes-Schiffer, S.; Benkovic, S. J. Probing the Electrostatics of Active Site Microenvironments along the Catalytic Cycle for Escherichia coli Dihydrofolate Reductase. J. Am. Chem. Soc. 2014, 136, 10349– 10360,  DOI: 10.1021/ja5038947
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    21
    Probing the electrostatics of active site microenvironments along the catalytic cycle for Escherichia coli dihydrofolate reductase
    Liu, C. Tony; Layfield, Joshua P.; Stewart, Robert J.; French, Jarrod B.; Hanoian, Philip; Asbury, John B.; Hammes-Schiffer, Sharon; Benkovic, Stephen J.
    Journal of the American Chemical Society (2014), 136 (29), 10349-10360CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Electrostatic interactions play an important role in enzyme catalysis by guiding ligand binding and facilitating chem. reactions. These electrostatic interactions are modulated by conformational changes occurring over the catalytic cycle. Here, the changes in active site electrostatic microenvironments were examd. for all enzyme complexes along the catalytic cycle of Escherichia coli dihydrofolate reductase (ecDHFR) by incorporation of thiocyanate probes at 2 site-specific locations in the active site. The electrostatics and degree of hydration of the microenvironments surrounding the probes were investigated with spectroscopic techniques and mixed quantum mech./mol. mech. (QM/MM) calcns. Changes in the electrostatic microenvironments along the catalytic environment led to different nitrile (CN) vibrational stretching frequencies and 13C NMR chem. shifts. These environmental changes arose from protein conformational rearrangements during catalysis. The QM/MM calcns. reproduced the exptl. measured vibrational frequency shifts of the thiocyanate probes across the catalyzed hydride transfer step, which spans the closed and occluded conformations of the enzyme. Anal. of the mol. dynamics trajectories provided insight into the conformational changes occurring between these 2 states and the resulting changes in classical electrostatics and specific H-bonding interactions. The elec. fields along the CN axes of the probes were decompd. into contributions from specific residues, ligands, and solvent mols. that make up the microenvironments around the probes. Moreover, calcn. of the elec. field along the hydride donor-acceptor axis, along with decompn. of this field into specific contributions, indicateds that the cofactor and substrate, as well as the enzyme, impose a substantial elec. field that facilitates hydride transfer. Overall, exptl. and theor. data provided evidence for significant electrostatic changes in the active site microenvironments due to conformational motion occurring over the catalytic cycle of ecDHFR.
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  22. 22
    (a) Bhowmick, A.; Sharma, S. C.; Head-Gordon, T. The Importance of the Scaffold for de Novo Enzymes: A Case Study with Kemp Eliminase. J. Am. Chem. Soc. 2017, 139, 5793– 5800,  DOI: 10.1021/jacs.6b12265
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    22a
    The Importance of the Scaffold for de Novo Enzymes: A Case Study with Kemp Eliminase
    Bhowmick, Asmit; Sharma, Sudhir C.; Head-Gordon, Teresa
    Journal of the American Chemical Society (2017), 139 (16), 5793-5800CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    We report elec. field values relevant to the reactant and transition states of designed Kemp eliminases KE07 and KE70, and their improved variants from lab. directed evolution (LDE), using atomistic simulations with the AMOEBA polarizable force field. We find that catalytic base residue contributes the most to the elec. field stabilization of the transition state of the LDE variants of the KE07 and KE70 enzymes, whereas the elec. fields of the remainder of the enzyme and solvent disfavor the catalytic reaction in both cases. By contrast, we show that the electrostatic environment play a large stabilizing role for the naturally occurring enzyme ketosteroid isomerase. These results suggest that LDE is ultimately a limited strategy for improving de novo enzymes since it is largely restricted to optimization of chem. positioning in the active site, thus yielding a ∼3 order magnitude improvement over the uncatalyzed reaction, an upper bound est. based on LDE applied to comparable de novo Kemp Eliminases and other enzymes. Instead de novo enzymic reactions would most productively benefit from optimization of the electrostatics of the protein scaffold in early stages of the computational design, utilizing elec. field optimization as guidance.
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    (b) Welborn, V. V.; Head-Gordon, T. Fluctuations of Electric Fields in the Active Site of the Enzyme Ketosteroid Isomerase. J. Am. Chem. Soc. 2019, 141, 12487– 12492,  DOI: 10.1021/jacs.9b05323
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    22b
    Fluctuations of Electric Fields in the Active Site of the Enzyme Ketosteroid Isomerase
    Welborn, Valerie Vaissier; Head-Gordon, Teresa
    Journal of the American Chemical Society (2019), 141 (32), 12487-12492CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    We report the effect of conformational dynamics on the fluctuations of elec. fields in the active site of the enzyme ketosteroid isomerase (KSI). While KSI is considered to be a rigid enzyme with little conformational variation to support different stages of the catalytic cycle, we show that KSI utilizes cooperative side chain motions of the entire protein scaffold outside the active site to modulate elec. fields in the active site. We find that while the active site residues Asp-40 and Tyr-16 maintain their elec. field contributions at all effective time scales, the conformational dynamics of a single active residue, Asp-103, promotes large elec. field fluctuations that contribute to different stages of the catalytic cycle, including the catalytic step and product release.
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  23. 23
    Vaissier, V.; Sharma, S. C.; Schaettle, K.; Zhang, T.; Head-Gordon, T. Computational Optimization of Electric Fields for Improving Catalysis of a Designed Kemp Eliminase. ACS Catal. 2018, 8, 219– 227,  DOI: 10.1021/acscatal.7b03151
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    23
    Computational Optimization of Electric Fields for Improving Catalysis of a Designed Kemp Eliminase
    Vaissier, Valerie; Sharma, Sudhir C.; Schaettle, Karl; Zhang, Taoran; Head-Gordon, Teresa
    ACS Catalysis (2018), 8 (1), 219-227CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
    Here we report a computational method to improve efficiency of a de novo designed Kemp Eliminase enzyme KE15, by identifying mutations that enhance elec. fields and chem. positioning of the substrate that contribute to free energy stabilization of the transition state. Starting from the design that has a kcat/KM of 27 M-1s-1, the most improved variant introduced 4 computationally targeted mutations to yield a kcat/KM of 403 M-1s-1, with almost all of the enzyme improvement realized through a 43-fold improvement in kcat, indicative of a direct impact on the chem. step. This work raises the prospect of computationally designing enzymes that achieve better efficiency with more minimal exptl. intervention using elec. field optimization as guidance.
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  24. 24
    Stuyver, T.; Huang, J.; Mallick, D.; Danovich, D.; Shaik, S. TITAN: A Code for Modeling and Generating Electric Fields─Features and Applications to Enzymatic Reactivity. J. Comput. Chem. 2020, 41, 74– 82,  DOI: 10.1002/jcc.26072
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    24
    TITAN: A Code for Modeling and Generating Electric Fields-Features and Applications to Enzymatic Reactivity
    Stuyver, Thijs; Huang, Jing; Mallick, Dibyendu; Danovich, David; Shaik, Sason
    Journal of Computational Chemistry (2020), 41 (1), 74-82CODEN: JCCHDD; ISSN:0192-8651. (John Wiley & Sons, Inc.)
    We present here a versatile computational code named "elec. fIeld generaTion And maNipulation (TITAN)," capable of generating various types of external elec. fields, as well as quantifying the local (or intrinsic) elec. fields present in proteins and other biol. systems according to Coulomb's Law. The generated elec. fields can be coupled with quantum mechanics (QM), mol. mechanics (MM), QM/MM, and mol. dynamics calcns. in most available software packages. The capabilities of the TITAN code are illustrated throughout the text with the help of examples. We end by presenting an application, in which the effects of the local elec. field on the hydrogen transfer reaction in cytochrome P 450 OleTJE enzyme and the modifications induced by the application of an oriented external elec. field are examd. We find that the protein matrix in P 450 OleTJE acts as a moderate catalyst and that orienting an external elec. field along the Fe-O bond of compd. I has the biggest impact on the reaction barrier. The induced catalysis/inhibition correlates with the calcd. spin d. on the O-atom. © 2019 Wiley Periodicals, Inc.
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  25. 25
    Shaik, S.; Danovich, D.; Dubey, K. D.; Stuyver, T. The Impact of Electric Fields on Chemical Structure and Reactivity. In Effects of Electric Fields on Structure and Reactivity: New Horizons in Chemistry; Shaik, S.; Stuyver, T., Eds.; Royal Society of Chemistry: Cambridge, 2021; Chapter 2, pp 12– 70.
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  26. 26
    (a) Luis, J. M.; Duran, M.; Andrés, J. L. A Systematic and Feasible Method for Computing Nuclear Contributions to Electrical Properties of Polyatomic Molecules. J. Chem. Phys. 1997, 107, 1501– 1512,  DOI: 10.1063/1.474503
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    26a
    A systematic and feasible method for computing nuclear contributions to electrical properties of polyatomic molecules
    Luis, Josep M.; Duran, Miquel; Andres, Jose L.
    Journal of Chemical Physics (1997), 107 (5), 1501-1512CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    An analytic method to evaluate nuclear contributions to elec. properties (dipole moment, polarizability, hyperpolarizability) of polyat. mols. is presented. Such contributions control changes induced by an elec. field on equil. geometry (nuclear relaxation contribution) and vibrational motion (vibrational contribution) of a mol. system. Expressions to compute the nuclear contributions have been derived from a power series expansion of the potential energy. These contributions to the elec. properties are given in terms of energy derivs. with respect to normal coordinates, elec. field intensity or both. Only one calcn. of such derivs. at the field-free equil. geometry is required. To shown the useful efficiency of the anal. evaluation of elec. properties (the so-called AEEP method), results for calcns. on water and pyridine at the SCF/TZ2P and the MP2/TZ2P levels of theory are reported. The results obtained are compared with previous theor. calcns. and with exptl. values.
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    (b) Kirtman, B.; Luis, J. M.; Bishop, D. M. Simple Finite Field Method for Calculation of Static and Dynamic Vibrational Hyperpolarizabilities: Curvature Contributions. J. Chem. Phys. 1998, 108, 10008– 10012,  DOI: 10.1063/1.476460
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    26b
    Simple finite field method for calculation of static and dynamic vibrational hyperpolarizabilities: Curvature contributions
    Kirtman, Bernard; Luis, Josep M.; Bishop, David M.
    Journal of Chemical Physics (1998), 108 (24), 10008-10012CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    In the static field limit, the vibrational hyperpolarizability consists of two contributions due to: (1) the shift in the equil. geometry (known as nuclear relaxation), and (2) the change in the shape of the potential energy surface (known as curvature). Simple finite field methods were previously developed for evaluating these static field contributions and also for detg. the effect of nuclear relaxation on dynamic vibrational hyperpolarizabilities in the infinite frequency approxn. In this paper the finite field approach is extended to include, within the infinite frequency approxn., the effect of curvature on the major dynamic nonlinear optical processes.
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    (c) Luis, J. M.; Martí, J.; Duran, M.; Andrés, J. L.; Kirtman, B. Nuclear Relaxation Contribution to Static and Dynamic (Infinite Frequency Approximation) Nonlinear Optical Properties by means of Electrical Property Expansions: Application to HF, CH4, CF4, and SF6. J. Chem. Phys. 1998, 108, 4123– 4130,  DOI: 10.1063/1.475810
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    26c
    Nuclear relaxation contribution to static and dynamic (infinite frequency approximation) nonlinear optical properties by means of electrical property expansions: Application to HF, CH4, CF4, and SF6
    Luis, Josep M.; Marti, Josep; Duran, Miquel; Andres, Jose L.; Kirtman, Bernard
    Journal of Chemical Physics (1998), 108 (10), 4123-4130CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    Elec. property deriv. expressions are presented for the nuclear relaxation contribution to static and dynamic (infinite frequency approxn.) nonlinear optical properties. For CF4 and SF6, as opposed to HF and CH4, a term that is quadratic in the vibrational anharmonicity (and not previously evaluated for any mol.) makes an important contribution to the static 2nd vibrational hyperpolarizability of CF4 and SF6. A comparison between calcd. and exptl. values for the difference between the (anisotropic) Kerr effect and elec. field induced 2nd-harmonic generation shows that, at the Hartree-Fock level, the nuclear relaxation/infinite frequency approxn. gives the correct trend (in the series CH4, CF4, SF6) but is of the order of 50% too small.
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  27. 27
    (a) Torrent-Sucarrat, M.; Solà, M.; Duran, M.; Luis, J. M.; Kirtman, B. Initial Convergence of the Perturbation Series Expansion for Vibrational Nonlinear Optical Properties. J. Chem. Phys. 2002, 116, 5363– 5373,  DOI: 10.1063/1.1453953
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    27a
    Initial convergence of the perturbation series expansion for vibrational nonlinear optical properties
    Torrent-Sucarrat, Miquel; Sola, Miquel; Duran, Miquel; Luis, Josep M.; Kirtman, Bernard
    Journal of Chemical Physics (2002), 116 (13), 5363-5373CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    Ab initio Hartree-Fock and MP2 calcns. of the longitudinal (hyper)polarizability - including the static electronic, static zero-point vibrational av. (ZPVA), and pure vibrational (static and dynamic) contributions - were carried out on a set of 7 typical medium size conjugated nonlinear optical (NLO) mols. The ZPVA is obtained through 1st-order in mech. plus elec. anharmonicity. Based on phys. nuclear relaxation considerations the individual (square bracket) terms that contribute to the pure vibrational (hyper)polarizability are then taken into account through 3rd-, 4th-, or 5th-order depending upon the type of term. In order to carry out the correlated treatment, field-induced coordinates and a special finite field technique are used. Correlation leads to very substantial differences in the abs. and relative values of the various contributions. In comparison to the electronic term the ZPVA correction is usually small but in 1 case is over 2/3 as large. Both static and dynamic pure vibrational contributions are commonly of a magnitude that is comparable to, or are larger than, the electronic term. The higher-order pure vibration terms are often large. For dynamic processes they can be almost as important as the lowest-order terms; for static (hyper)polarizabilities they can be more important. For typical NLO mols., the initial convergence behavior of the perturbation series in mech. and elec. anharmonicity requires further study.
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    (b) Torrent-Sucarrat, M.; Solà, M.; Duran, M.; Luis, J. M.; Kirtman, B. Basis Set and Electron Correlation Effects on ab Initio Electronic and Vibrational Nonlinear Optical Properties of Conjugated Organic Molecules. J. Chem. Phys. 2003, 118, 711– 718,  DOI: 10.1063/1.1521725
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    27b
    Basis set and electron correlation effects on ab initio electronic and vibrational nonlinear optical properties of conjugated organic molecules
    Torrent-Sucarrat, Miquel; Sola, Miquel; Duran, Miquel; Luis, Josep M.; Kirtman, Bernard
    Journal of Chemical Physics (2003), 118 (2), 711-718CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    We have studied how the calcn. of electronic and vibrational contributions to nonlinear optical properties of three representative π-conjugated org. mols. is affected by the choice of basis set and the inclusion of electron correlation effects. The 6-31G basis does not always provide even qual. accuracy. For semiquant. accuracy a 6-31+G(d) basis is sufficient. Although, as compared to QCISD, a second-order Moller-Plesset (MP2) treatment often yields a substantial fraction of the electron correlation contribution, our MP2 results for the sep. electronic and vibrational terms are not consistently of semiquant. accuracy. Nevertheless, at the MP2 level the ratio between the vibrational and electronic contributions is satisfactorily reproduced.
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    (c) Torrent-Sucarrat, M.; Solà, M.; Duran, M.; Luis, J. M.; Kirtman, B. Basis Set and Electron Correlation Effects on Initial Convergence for Vibrational Nonlinear Optical Properties of Conjugated Organic Molecules. J. Chem. Phys. 2004, 120, 6346– 6355,  DOI: 10.1063/1.1667465
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    27c
    Basis set and electron correlation effects on initial convergence for vibrational nonlinear optical properties of conjugated organic molecules
    Torrent-Sucarrat, Miquel; Sola, Miquel; Duran, Miquel; Luis, Josep M.; Kirtman, Bernard
    Journal of Chemical Physics (2004), 120 (14), 6346-6355CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    Using three typical π-conjugated mols. (1,3,5-hexatriene, 1-formyl-6-hydroxyhexa-1,3,5-triene, and 1,1-diamino-6,6-dinitrohexa-1,3,5-triene) we investigate the level of ab initio theory necessary to produce reliable values for linear and nonlinear optical properties, with emphasis on the vibrational contributions that are known to be important or potentially important. These calcns. are made feasible by employing field-induced coordinates in combination with a finite field procedure. For many, but not all, purposes the MP2/6-31+G(d) level is adequate. Based on our results the convergence of the usual perturbation treatment for vibrational anharmonicity was examd. Although this treatment is initially convergent in most circumstances, a problematic situation has been identified.
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    (d) Torrent-Sucarrat, M.; Luis, J. M.; Kirtman, B. Variational Calculation of Vibrational Linear and Nonlinear Optical Properties. J. Chem. Phys. 2005, 122, 204108  DOI: 10.1063/1.1909031
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    27d
    Variational calculation of vibrational linear and nonlinear optical properties
    Torrent-Sucarrat, Miquel; Luis, Josep M.; Kirtman, Bernard
    Journal of Chemical Physics (2005), 122 (20), 204108/1-204108/10CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    A variational approach for reliably calcg. vibrational linear and nonlinear optical properties of mols. with large elec. and/or mech. anharmonicity is introduced. This approach utilizes a self-consistent soln. of the vibrational Schrodinger equation for the complete field-dependent potential-energy surface and, then, adds higher-level vibrational correlation corrections as desired. An initial application is made to static properties for three mols. of widely varying anharmonicity using the lowest-level vibrational correlation treatment (i.e., vibrational Moller-Plesset perturbation theory). Our results indicate when the conventional Bishop-Kirtman perturbation method can be expected to break down and when high-level vibrational correlation methods are likely to be required. Future improvements and extensions are discussed.
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  28. 28
    Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Petersson, G. A.; Nakatsuji, H.; Li, X.; Caricato, M.; Marenich, A. V.; Bloino, J.; Janesko, B. G.; Gomperts, R.; Mennucci, B.; Hratchian, H. P.; Ortiz, J. V.; Izmaylov, A. F.; Sonnenberg, J. L.; Williams; ; Ding, F.; Lipparini, F.; Egidi, F.; Goings, J.; Peng, B.; Petrone, A.; Henderson, T.; Ranasinghe, D.; Zakrzewski, V. G.; Gao, J.; Rega, N.; Zheng, G.; Liang, W.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Throssell, K.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M. J.; Heyd, J. J.; Brothers, E. N.; Kudin, K. N.; Staroverov, V. N.; Keith, T. A.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A. P.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Millam, J. M.; Klene, M.; Adamo, C.; Cammi, R.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Farkas, O.; Foresman, J. B.; Fox, D. J. Gaussian 16, revision C.01; Gaussian, Inc.: Wallingford, CT, 2016.
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    There is no corresponding record for this reference.
  29. 29
    (a) Vosko, S. H.; Wilk, L.; Nusair, M. Accurate Spin-Dependent Electron Liquid Correlation Energies for Local Spin Density Calculations: a Critical Analysis. Can. J. Phys. 1980, 58, 1200– 1211,  DOI: 10.1139/p80-159
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    29a
    Accurate spin-dependent electron liquid correlation energies for local spin density calculations: a critical analysis
    Vosko, S. H.; Wilk, L.; Nusair, M.
    Canadian Journal of Physics (1980), 58 (8), 1200-11CODEN: CJPHAD; ISSN:0008-4204.
    Various approx. forms for the correlation energy per particle of the spin-polarized homogeneous electron gas that have frequently been used in applications of the local spin d. approxn. to the exchange-correlation energy functional are assessed. By accurately recalcg. the RPA correlation energy as a function of electron d. and spin polarization, the inadequacies of the usual approxn. for interpolating between the para- and ferro-magnetic states are demonstrated and an accurate new interpolation formula is presented. A Pade approximant technique was used to accurately interpolate the recent Monte Carlo results. These results can be combined with the RPA spin-dependence so as to produce a correlation energy for a spin-polarized homogeneous electron gas with an estd. max. error of 1 mRy and thus should reliably det. the magnitude of non-local corrections to the local spin d. approxn. in real systems.
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    (b) Lee, C.; Yang, W.; Parr, R. G. Development of the Colle-Salvetti Correlation-Energy Formula into a Functional of the Electron Density. Phys. Rev. B 1988, 37, 785– 789,  DOI: 10.1103/PhysRevB.37.785
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    29b
    Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density
    Lee, Chengteh; Yang, Weitao; Parr, Robert G.
    Physical Review B: Condensed Matter and Materials Physics (1988), 37 (2), 785-9CODEN: PRBMDO; ISSN:0163-1829.
    A correlation-energy formula due to R. Colle and D. Salvetti (1975), in which the correlation energy d. is expressed in terms of the electron d. and a Laplacian of the 2nd-order Hartree-Fock d. matrix, is restated as a formula involving the d. and local kinetic-energy d. On insertion of gradient expansions for the local kinetic-energy d., d.-functional formulas for the correlation energy and correlation potential are then obtained. Through numerical calcns. on a no. of atoms, pos. ions, and mols., of both open- and closed-shell type, it is demonstrated that these formulas, like the original Colle-Salvetti formulas, give correlation energies within a few percent.
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    (c) Becke, A. D. Density-Functional Thermochemistry. III. The Role of Exact Exchange. J. Chem. Phys. 1993, 98, 5648– 5652,  DOI: 10.1063/1.464913
    Google Scholar
    29c
    Density-functional thermochemistry. III. The role of exact exchange
    Becke, Axel D.
    Journal of Chemical Physics (1993), 98 (7), 5648-52CODEN: JCPSA6; ISSN:0021-9606.
    Despite the remarkable thermochem. accuracy of Kohn-Sham d.-functional theories with gradient corrections for exchange-correlation, the author believes that further improvements are unlikely unless exact-exchange information is considered. Arguments to support this view are presented, and a semiempirical exchange-correlation functional (contg. local-spin-d., gradient, and exact-exchange terms) is tested for 56 atomization energies, 42 ionization potentials, 8 proton affinities, and 10 total at. energies of first- and second-row systems. This functional performs better than previous functionals with gradient corrections only, and fits expt. atomization energies with an impressively small av. abs. deviation of 2.4 kcal/mol.
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  30. 30
    Ditchfield, R.; Hehre, W. J.; Pople, J. A. Self-Consistent Molecular-Orbital Methods. IX. An Extended Gaussian-Type Basis for Molecular-Orbital Studies of Organic Molecules. J. Chem. Phys. 1971, 54, 724– 728,  DOI: 10.1063/1.1674902
    Google Scholar
    30
    Self-consistent molecular-orbital methods. IX. Extended Gaussian-type basis for molecular-orbital studies of organic molecules
    Ditchfield, R.; Hehre, Warren J.; Pople, John A.
    Journal of Chemical Physics (1971), 54 (2), 724-8CODEN: JCPSA6; ISSN:0021-9606.
    An extended basis set of at. functions expressed as fixed linear combinations of Gaussian functions is presented for H and the first-row atoms C to F. In this set. described as 4-31 G, each inner shell is represented by a single basis function taken as a sum of 4 Gaussians, and each valence orbital is split into inner and outer parts described by 3 and 1 Gaussian function, resp. The expansion coeffs. and Gaussian exponents are detd. by minimizing the total calcd. energy of the at. ground state. This basis set is then used in single-determinant MO studies of a group of small polyat. mols. Optimization of valence-shell scaling factors shows that considerable rescaling of at. functions occurs in mols., the largest effects being obsd. for H and C. However, the range of optimum scale factors for each atom is small enough to allow the selection of a std. mol. set. The use of this std. basis gives theoretical equil. geometries in reasonable agreement with expt.
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  31. 31
    Grimme, S.; Antony, J.; Ehrlich, S.; Krieg, H. A Consistent and Accurate ab Initio Parametrization of Density Functional Dispersion Correction (DFT-D) for the 94 Elements H-Pu. J. Chem. Phys. 2010, 132, 154104  DOI: 10.1063/1.3382344
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    31
    A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu
    Grimme, Stefan; Antony, Jens; Ehrlich, Stephan; Krieg, Helge
    Journal of Chemical Physics (2010), 132 (15), 154104/1-154104/19CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    The method of dispersion correction as an add-on to std. Kohn-Sham d. functional theory (DFT-D) has been refined regarding higher accuracy, broader range of applicability, and less empiricism. The main new ingredients are atom-pairwise specific dispersion coeffs. and cutoff radii that are both computed from first principles. The coeffs. for new eighth-order dispersion terms are computed using established recursion relations. System (geometry) dependent information is used for the first time in a DFT-D type approach by employing the new concept of fractional coordination nos. (CN). They are used to interpolate between dispersion coeffs. of atoms in different chem. environments. The method only requires adjustment of two global parameters for each d. functional, is asymptotically exact for a gas of weakly interacting neutral atoms, and easily allows the computation of at. forces. Three-body nonadditivity terms are considered. The method has been assessed on std. benchmark sets for inter- and intramol. noncovalent interactions with a particular emphasis on a consistent description of light and heavy element systems. The mean abs. deviations for the S22 benchmark set of noncovalent interactions for 11 std. d. functionals decrease by 15%-40% compared to the previous (already accurate) DFT-D version. Spectacular improvements are found for a tripeptide-folding model and all tested metallic systems. The rectification of the long-range behavior and the use of more accurate C6 coeffs. also lead to a much better description of large (infinite) systems as shown for graphene sheets and the adsorption of benzene on an Ag(111) surface. For graphene it is found that the inclusion of three-body terms substantially (by about 10%) weakens the interlayer binding. We propose the revised DFT-D method as a general tool for the computation of the dispersion energy in mols. and solids of any kind with DFT and related (low-cost) electronic structure methods for large systems. (c) 2010 American Institute of Physics.
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  32. 32
    (a) Johnson, E. R.; Becke, A. D. A Post-Hartree-Fock Model of Intermolecular Interactions: Inclusion of Higher-Order Corrections. J. Chem. Phys. 2006, 124, 174104  DOI: 10.1063/1.2190220
    Google Scholar
    32a
    A post-Hartree-Fock model of intermolecular interactions: Inclusion of higher-order corrections
    Johnson, Erin R.; Becke, Axel D.
    Journal of Chemical Physics (2006), 124 (17), 174104/1-174104/9CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    We have previously demonstrated that the dipole moment of the exchange hole can be used to derive intermol. C6 dispersion coeffs. [J. Chem. Phys. 122, 154104 (2005)]. This was subsequently the basis for a novel post-Hartree-Fock model of intermol. interactions [J. Chem. Phys. 123, 024101 (2005)]. In the present work, the model is extended to include higher-order dispersion coeffs. C8 and C10. The extended model performs very well for prediction of intermonomer sepns. and binding energies of 45 van der Waals complexes. In particular, it performs twice as well as basis-set extrapolated MP2 theory for dispersion-bound complexes, with minimal computational cost.
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    (b) Grimme, S.; Ehrlich, S.; Goerigk, L. Effect of the Damping Function in Dispersion Corrected Density Functional Theory. J. Comput. Chem. 2011, 32, 1456– 1465,  DOI: 10.1002/jcc.21759
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    32b
    Effect of the damping function in dispersion corrected density functional theory
    Grimme, Stefan; Ehrlich, Stephan; Goerigk, Lars
    Journal of Computational Chemistry (2011), 32 (7), 1456-1465CODEN: JCCHDD; ISSN:0192-8651. (John Wiley & Sons, Inc.)
    It is shown by an extensive benchmark on mol. energy data that the math. form of the damping function in DFT-D methods has only a minor impact on the quality of the results. For 12 different functionals, a std. "zero-damping" formula and rational damping to finite values for small interat. distances according to Becke and Johnson (BJ-damping) has been tested. The same (DFT-D3) scheme for the computation of the dispersion coeffs. is used. The BJ-damping requires one fit parameter more for each functional (three instead of two) but has the advantage of avoiding repulsive interat. forces at shorter distances. With BJ-damping better results for nonbonded distances and more clear effects of intramol. dispersion in four representative mol. structures are found. For the noncovalently-bonded structures in the S22 set, both schemes lead to very similar intermol. distances. For noncovalent interaction energies BJ-damping performs slightly better but both variants can be recommended in general. The exception to this is Hartree-Fock that can be recommended only in the BJ-variant and which is then close to the accuracy of cor. GGAs for non-covalent interactions. According to the thermodn. benchmarks BJ-damping is more accurate esp. for medium-range electron correlation problems and only small and practically insignificant double-counting effects are obsd. It seems to provide a phys. correct short-range behavior of correlation/dispersion even with unmodified std. functionals. In any case, the differences between the two methods are much smaller than the overall dispersion effect and often also smaller than the influence of the underlying d. functional. © 2011 Wiley Periodicals, Inc.; J. Comput. Chem., 2011.
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  33. 33
    (a) Perdew, J. P. Density-Functional Approximation for the Correlation Energy of the Inhomogeneous Electron Gas. Phys. Rev. B 1986, 33, 8822– 8824,  DOI: 10.1103/PhysRevB.33.8822
    Google Scholar
    33a
    Density-functional approximation for the correlation energy of the inhomogeneous electron gas
    Perdew
    Physical review. B, Condensed matter (1986), 33 (12), 8822-8824 ISSN:0163-1829.
    There is no expanded citation for this reference.
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    (b) Becke, A. D. Density-Functional Exchange-Energy Approximation with Correct Asymptotic Behavior. Phys. Rev. A 1988, 38, 3098– 3100,  DOI: 10.1103/PhysRevA.38.3098
    Google Scholar
    33b
    Density-functional exchange-energy approximation with correct asymptotic behavior
    Becke, A. D.
    Physical Review A: Atomic, Molecular, and Optical Physics (1988), 38 (6), 3098-100CODEN: PLRAAN; ISSN:0556-2791.
    Current gradient-cor. d.-functional approxns. for the exchange energies of at. and mol. systems fail to reproduce the correct 1/r asymptotic behavior of the exchange-energy d. A gradient-cor. exchange-energy functional is given with the proper asymptotic limit. This functional, contg. only one parameter, fits the exact Hartree-Fock exchange energies of a wide variety of at. systems with remarkable accuracy, surpassing the performance of previous functionals contg. two parameters or more.
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  34. 34
    Murgida, D. H.; Hildebrandt, P. Electron-Transfer Processes of Cytochrome c at Interfaces. New Insights by Surface-Enhanced Resonance Raman Spectroscopy. Acc. Chem. Res. 2004, 37, 854– 861,  DOI: 10.1021/ar0400443
    Google Scholar
    34
    Electron-Transfer Processes of Cytochrome c at Interfaces. New Insights by Surface-Enhanced Resonance Raman Spectroscopy
    Murgida, Daniel H.; Hildebrandt, Peter
    Accounts of Chemical Research (2004), 37 (11), 854-861CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
    A review. The heme protein cytochrome c acts as an electron carrier at the mitochondrial-membrane interface and thus exerts its function under the influence of strong elec. fields. To assess possible consequences of elec. fields on the redox processes of cytochrome c, the protein can be immobilized to self-assembled monolayers on electrodes and studied by surface-enhanced resonance Raman spectroscopy. Such model systems may mimic some essential features of biol. interfaces including local elec. field strengths. It is shown that physiol. relevant elec. field strengths can effectively modulate the electron-transfer dynamics and induce conformational transitions.
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  35. 35
    Dubey, K. D.; Stuyver, T.; Kalita, S.; Shaik, S. Solvent Organization and Rate Regulation of a Menshutkin Reaction by Oriented External Electric Fields are Revealed by Combined MD and QM/MM Calculations. J. Am. Chem. Soc. 2020, 142, 9955– 9965,  DOI: 10.1021/jacs.9b13029
    Google Scholar
    There is no corresponding record for this reference.
  36. 36
    Fernández, S.; Franco, F.; Casadevall, C.; Martin-Diaconescu, V.; Luis, J. M.; Lloret-Fillol, J. A Unified Electro- and Photocatalytic CO2 to CO Reduction Mechanism with Aminopyridine Cobalt Complexes. J. Am. Chem. Soc. 2020, 142, 120– 133,  DOI: 10.1021/jacs.9b06633
    Google Scholar
    36
    A Unified Electro- and Photocatalytic CO2 to CO Reduction Mechanism with Aminopyridine Cobalt Complexes
    Fernandez, Sergio; Franco, Federico; Casadevall, Carla; Martin-Diaconescu, Vlad; Luis, Josep M.; Lloret-Fillol, Julio
    Journal of the American Chemical Society (2020), 142 (1), 120-133CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    A mechanistic understanding of electro- and photocatalytic CO2 redn. is crucial to develop strategies to overcome catalytic bottlenecks. In this regard, for a new CO2-to-CO redn. cobalt aminopyridine catalyst, a detailed exptl. and theor. mechanistic study is herein presented toward the identification of bottlenecks and potential strategies to alleviate them. The combination of electrochem. and in situ spectroelectrochem. together with spectroscopic techniques led us to identify elusive key electrocatalytic intermediates derived from complex [LN4Co(OTf)2] (1) (LN4 = 1-[2-pyridylmethyl]-4,7-dimethyl-1,4,7-triazacyclononane) such as a highly reactive cobalt(I) (1(I)) and a cobalt(I) carbonyl (1(I)-CO) species. The combination of spectroelectrochem. studies under CO2, 13CO2, and CO with DFT disclosed that 1(I) reacts with CO2 to form the pivotal 1(I)-CO intermediate at the 1(II/I) redox potential. However, at this redn. potential, the formation of 1(I)-CO restricts the electrocatalysis due to the endergonicity of the CO release step. In agreement with the exptl. obsd. CO2-to-CO electrocatalysis at the CoI/0 redox potential, computational studies suggested that the electrocatalytic cycle involves striking metal carbonyls. In contrast, under photochem. conditions, the catalysis smoothly proceeds at the 1(II/I) redox potential. Under the latter conditions, it is proposed that the electron transfer to form 1(I)-CO from 1(II)-CO is under diffusion control. Then, the CO release from 1(II)-CO is kinetically favored, facilitating the catalysis. Finally, we have found that visible-light irradn. has a pos. impact under electrocatalytic conditions. We envision that light irradn. can serve as an effective strategy to circumvent the CO poisoning and improve the performance of CO2 redn. mol. catalysts.
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  37. 37
    Hoffmann, R.; Schleyer, P. v. R.; Schaefer, H. F., III Predicting Molecules─More Realism, Please!. Angew. Chem., Int. Ed. 2008, 47, 7164– 7167,  DOI: 10.1002/anie.200801206
    Google Scholar
    37
    Predicting molecules--more realism, please!
    Hoffmann Roald; Schleyer Paul von Rague; Schaefer Henry F 3rd
    Angewandte Chemie (International ed. in English) (2008), 47 (38), 7164-7 ISSN:.
    There is no expanded citation for this reference.
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  38. 38
    (a) Huisgen, R. 1,3-Dipolar Cycloadditions. Past and Future. Angew. Chem., Int. Ed. 1963, 2, 565– 598,  DOI: 10.1002/anie.196305651
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    There is no corresponding record for this reference.
    (b) Huisgen, R. 1,3-Dipolar Cycloaddition Chemistry; John Wiley & Sons, Inc.: New York, 1984; Vol. 1, pp 1– 176.
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    There is no corresponding record for this reference.
    (c) Breugst, M.; Reissig, H.-U. The Huisgen Reaction: Milestones of the 1,3-Dipolar Cycloaddition. Angew. Chem., Int. Ed. 2020, 59, 12293– 12307,  DOI: 10.1002/anie.202003115
    Google Scholar
    38c
    The Huisgen Reaction: Milestones of the 1,3-Dipolar Cycloaddition
    Breugst, Martin; Reissig, Hans-Ulrich
    Angewandte Chemie, International Edition (2020), 59 (30), 12293-12307CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A review. The concept of 1,3-dipolar cycloaddns. was presented by Rolf Huisgen 60 years ago. Previously unknown reactive intermediates, for example azomethine ylides, were introduced to org. chem. and the (3+2) cycloaddns. of 1,3-dipoles to multiple-bond systems (Huisgen reaction) developed into one of the most versatile synthetic methods in heterocyclic chem. In this Review, the authors present the history of this research area, highlight important older reports, and describe the evolution and further development of the concept. The most important mechanistic and synthetic results are discussed. Quantum-mech. calcns. support the concerted mechanism always favored by R. Huisgen; however, in extreme cases intermediates may be involved. The impact of 1,3-dipolar cycloaddns. on the click chem. concept of K. B. Sharpless will also be discussed.
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  39. 39
    (a) de Cózar, A.; Cossío, F. P. Stereocontrolled (3+2) Cycloadditions between Azomethine Ylides and Dipolarophiles: a Fruitful Interplay between Theory and Experiment. Phys. Chem. Chem. Phys. 2011, 13, 10858– 10868,  DOI: 10.1039/c1cp20682f
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    39a
    Stereocontrolled (3+2) cycloadditions between azomethine ylides and dipolarophiles: a fruitful interplay between theory and experiment
    de Cozar, Abel; Cossio, Fernando P.
    Physical Chemistry Chemical Physics (2011), 13 (23), 10858-10868CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    A review. In this article we present recent developments in (3+2) cycloaddns. with special emphasis on 1,3-dipolar reactions involving azomethine ylides and alkenes possessing electron withdrawing groups. It is found that there is not a general mechanism for these reactions since both concerted arom. [π4s+π2s] mechanisms and stepwise processes involving zwitterionic intermediates can be found. These computational models can be extended to analyze the role of chiral catalysts in these reactions in order to understand the nature of the catalytic cycle and the origins of chiral induction.
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    (b) Arrastia, I.; Arrieta, A.; Cossío, F. P. Application of 1,3-Dipolar Reactions between Azomethine Ylides and Alkenes to the Synthesis of Catalysts and Biologically Active Compounds. Eur. J. Org. Chem. 2018, 2018, 5889– 5904,  DOI: 10.1002/ejoc.201800911
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    39b
    Application of 1,3-Dipolar Reactions between Azomethine Ylides and Alkenes to the Synthesis of Catalysts and Biologically Active Compounds
    Arrastia, Iosune; Arrieta, Ana; Cossio, Fernando P.
    European Journal of Organic Chemistry (2018), 2018 (43), 5889-5904CODEN: EJOCFK; ISSN:1099-0690. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A review. The (3+2) cycloaddn. between azomethine ylides and alkenes is an efficient, convergent and stereocontrolled method for the synthesis of unnatural pyrrolidine and proline scaffolds. In this review, the application of this reaction to the synthesis of enantiopure organometallic ligands for asym. catalysis is presented first. These new EhuPhos ligands can participate in a second generation of 1,3-dipolar reactions that generate an offspring of unnatural proline derivs. that behave as efficient organocatalysts. These densely substituted unnatural L-proline derivs. exhibit distinct features, different to those described for natural L-proline and its derivs. Finally, several examples of biol. active proline derivs. obtained by means of (3+2) cycloaddns. involving azomethine ylides are presented. These applications show the character of privileged structures of these polysubstituted pyrrolidine rings.
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  40. 40
    Arrieta, A.; Otaegui, D.; Zubia, A.; Cossío, F. P.; Díaz-Ortiz, A.; de la Hoz, A.; Herrero, M. A.; Prieto, P.; Foces-Foces, C.; Pizarro, J. L.; Arriortua, M. I. Solvent-Free Thermal and Microwave-Assisted [3 + 2] Cycloadditions between Stabilized Azomethine Ylides and Nitrostyrenes. An Experimental and Theoretical Study. J. Org. Chem. 2007, 72, 4313– 4322,  DOI: 10.1021/jo062672z
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    40
    Solvent-Free Thermal and Microwave-Assisted [3 + 2] Cycloadditions between Stabilized Azomethine Ylides and Nitrostyrenes. An Experimental and Theoretical Study
    Arrieta, Ana; Otaegui, Dorleta; Zubia, Aizpea; Cossio, Fernando P.; Diaz-Ortiz, Angel; de la Hoz, Antonio; Herrero, M. Antonia; Prieto, Pilar; Foces-Foces, Concepcion; Pizarro, Jose L.; Arriortua, Maria I.
    Journal of Organic Chemistry (2007), 72 (12), 4313-4322CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)
    The stereochem. outcomes obsd. in the thermal and microwave-assisted [3 + 2] cycloaddn. between stabilized azomethine ylides and nitrostyrenes have been analyzed using exptl. and computational approaches. It has been obsd. that, in the absence of solvent, three stereoisomers are formed, both under classical heating conditions and under microwave irradn. This result contrasts with that obsd. in soln. under classical thermal conditions. The 4-nitropyrrolidines obtained in this way can be aromatized under further microwave irradn. to yield mixts. of pyrroles and 4-nitropyrroles. It is found that ground state cycloaddns. between imines and nitrostyrenes take place by three-step mechanisms. The first step involves enolization of the starting imine, and this is followed by a pseudopericyclic 10-electron [1.4]-hydrogen shift. Finally, the cycloaddn. takes place by a relatively asynchronous arom. six-electron supra-supra thermal mechanism.
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  41. 41
    Rivilla, I.; Odriozola-Gimeno, M.; Aires, A.; Gimeno, A.; Jiménez-Barbero, J.; Torrent-Sucarrat, M.; Cortajarena, A. L.; Cossío, F. P. Discovering Biomolecules with Huisgenase Activity: Designed Repeat Proteins as Biocatalysts for (3 + 2) Cycloadditions. J. Am. Chem. Soc. 2020, 142, 762– 776,  DOI: 10.1021/jacs.9b06823
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    41
    Discovering Biomolecules with Huisgenase Activity: Designed Repeat Proteins as Biocatalysts for (3 + 2) Cycloadditions
    Rivilla, Ivan; Odriozola-Gimeno, Mikel; Aires, Antonio; Gimeno, Ana; Jimenez-Barbero, Jesus; Torrent-Sucarrat, Miquel; Cortajarena, Aitziber L.; Cossio, Fernando P.
    Journal of the American Chemical Society (2020), 142 (2), 762-776CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Designed repeat proteins catalyze the 1,3-dipolar reaction between an imine and a π-deficient dipolarophile in THF soln. to form unnatural nitroproline esters, a reaction that no enzyme can catalyze. NMR studies and mutation expts. show that both acidic and basic residues can catalyze the reaction. The diastereocontrol of the reaction depends on the flexibility of the protein and on the no. and location of the active lysine and glutamate residues, which can participate independently or forming dyads that promote the formation of unusual diastereomeric cycloadducts. QM/MM calcns. permit to rationalize the origins of this Huisgenase activity and of its diastereocontrol.
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  42. 42
    Diels, O.; Alder, K. Synthesen in der Hydroaromatischen Reihe. Justus Liebigs Ann. Chem. 1928, 460, 98– 122,  DOI: 10.1002/jlac.19284600106
    Google Scholar
    42
    Syntheses in the hydroaromatic series. I. Addition of "diene" hydrocarbons
    Diels, Otto; Alder, Kurt
    Justus Liebigs Annalen der Chemie (1928), 460 (), 98-122CODEN: JLACBF; ISSN:0075-4617.
    The cyclopentadienequinone of Albrecht (Ann. 348, 31(1906)) is considered to be an endo-methylene deriv. of a hydrogenated α-naphthoquinone (I); reduction with Zn and AcOH gives the dihydro deriv. (II), m. 34-5°; catalytic reduction of II gives nearly quant. endo-methylene-1,4-diketo-5,8-decahydronaphthalene (III), m. 56-7° (dioxime, m. 217-8° (decompn.)); further reduction with amalgamated Zn and fuming HCl gives endo-methylene-1,4-decalin (IV), b15 84-5°, b22 91°. Reduction of 25 g. of tetrahydrodi [cyclopentadienequinone] with amalgamated Zn and HCl gives 8 g. di-[endo-methylene]-1,4,5,8-tetradecahydroanthracene (V), b16 157-9°; heated with Se 8-10 hrs. at 360-80°, this yields di-[endo-methylene]-1,4,5,8-octahydroanthracene, m. 56°. α-Naphthoquinone and butadiene (VI) in EtOH, heated 3 hrs. at 100°, give Δ2-tetrahydroanthraquinone, m. 102-3°. Oxidation with CrO3 gives anthraquinone. One mol. CH:CH.CO.O.CO (VII) and 1 mol. CH:CH.CH:CH.CH2 in 5 parts C6H6 give nearly quant. cis-endo-methylene-3,6-Δ4-tetrahydrophthalic anhydride, m. 164-5°; heating a short time in H2O gives the acid, m. 177-9°. The Na salt, catalytically reduced, gives cis-endomethylene-3,6-hexahydrophthalic acid, m. 160-1°; AcCl gives the anhydride, m. 167-8°. The cis-acid, heated 2-3 hrs. with concd. HCl at 180-90°, gives the trans-acid, m. 194-5°, VI and VII in C6H6 give quant. cis-Δ4-tetrahydrophthalic anhydride, m. 103-4°; the free acid, m. 166°; catalytic reduction of the Na salt gives cis-hexahydrophthalic acid, m. 191°. Δ1,3-Dihydrobenzene and VII give the compd. C10H10O3(VIII), m. 147°. α-Phellandrene and VII give the compd. C14H18O3 (IX), m. 126-7°. Citraconic anhydride and cyclopentadiene give methyl-1-endo-methylene-3,6-Δ4-tetrahydrophthalic anhydride, m. 138°, while itaconic anhydride gives endo-methylene-2,5-Δ3-tetrahydrobenzene-1-carboxylic-1-acetic anhydride, m. 53-4°; the free acid, m. 150-1°. Acrylic acid gives endo-methylene-2,5-Δ3-tetrahydrobenzoic acid, b22 132-4°, whose Na salt is catalytically reduced to endo-methylene-2,5-hexahydrobenzoic acid, b13 125-7°, m. 62-3. Acrolein gives endo-methylene-2,5-tetrahydrobenzaldehyde, b22 70-2° (semicarbazone, m. 162°); condensation with cyclohexanone gives the compd. C22H26O, pale yellow, m. 105°. Reduction gives endo-methylene-2,5-hexahydrobenzaldehyde, b25 75-6 (semicarbazone, m. 141-2°; condensation product with cyclohexanone, C22H30O, m. 101-2°). Acrolein and butadiene, heated 1 hr. at 100°, give Δ3-tetrahydrobenzaldehyde, b13 51-2 (semicarbazone, m. 153-4°), which is catalytically reduced to hexahydrobenzaldehyde.
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  43. 43
    Fringuelli, F. T. A. The Diels–Alder Reaction: Selected Practical Methods.; John Wiley & Sons: Chichester, England, 2002.
    Google Scholar
    There is no corresponding record for this reference.
  44. 44
    (a) Rogers, F. E.; Quan, S. W. Thermochemistry of the Diels-Alder Reaction. III. Heat of addition of Cyclopentadiene to Maleic Anhydride. J. Phys. Chem. B. 1973, 77, 828– 831,  DOI: 10.1021/j100625a019
    Google Scholar
    There is no corresponding record for this reference.
    (b) Breslauer, K. J.; Kabakoff, D. S. Enthalpy of the Diels-Alder Reaction of Cyclopentadiene and Maleic Anhydride. J. Org. Chem. 1974, 39, 721– 722,  DOI: 10.1021/jo00919a034
    Google Scholar
    44b
    Enthalpy of the Diels-Alder reaction of cyclopentadiene and maleic anhydride
    Breslauer, Kenneth J.; Kabakoff, David S.
    Journal of Organic Chemistry (1974), 39 (5), 721-2CODEN: JOCEAH; ISSN:0022-3263.
    The enthalpy of the Diels-Alder reaction of cyclopentadiene and maleic anhydride was detd. by flow microcalorimetry. At 25.0° ΔHR = -24.8 ± 0.5 kcal/mole in dioxane soln. The method employed is potentially applicable to measurement of enthalpies of a wide variety of fast organic reactions in soln.
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  45. 45
    Yu, S.; Vermeeren, P.; Hamlin, T. A.; Bickelhaupt, F. M. How Oriented External Electric Fields Modulate Reactivity. Chem.─Eur. J. 2021, 27, 5683– 5693,  DOI: 10.1002/chem.202004906
    Google Scholar
    45
    How Oriented External Electric Fields Modulate Reactivity
    Yu, Song; Vermeeren, Pascal; Hamlin, Trevor A.; Bickelhaupt, F. Matthias
    Chemistry - A European Journal (2021), 27 (18), 5683-5693CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A judiciously oriented external elec. field (OEEF) can catalyze a wide range of reactions and can even induce endo/exo stereoselectivity of cycloaddn. reactions. The Diels-Alder reaction between cyclopentadiene and maleic anhydride is studied by using quant. activation strain and Kohn-Sham MO theory to pinpoint the origin of these catalytic and stereoselective effects. Our quant. model reveals that an OEEF along the reaction axis induces an enhanced electrostatic and orbital interaction between the reactants, which in turn lowers the reaction barrier. The stronger electrostatic interaction originates from an increased electron d. difference between the reactants at the reactive center, and the enhanced orbital interaction arises from the promoted normal electron demand donor-acceptor interaction driven by the OEEF. An OEEF perpendicular to the plane of the reaction axis solely stabilizes the exo pathway of this reaction, whereas the endo pathway remains unaltered and efficiently steers the endo/exo stereoselectivity. The influence of the OEEF on the inverse electron demand Diels-Alder reaction is also investigated; unexpectedly, it inhibits the reaction, as the elec. field now suppresses the crit. inverse electron demand donor-acceptor interaction.
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  46. 46
    Wannere, C. S.; Paul, A.; Herges, R.; Houk, K. N.; Schaefer, H. F., III; Schleyer, P. v. R. The Existence of Secondary Orbital Interactions. J. Comput. Chem. 2007, 28, 344– 361,  DOI: 10.1002/jcc.20532
    Google Scholar
    46
    The existence of secondary orbital interactions
    Wannere, Chaitanya S.; Paul, Ankan; Herges, Rainer; Houk, K. N.; Schaefer, Henry F., III; Schleyer, Paul von Rague
    Journal of Computational Chemistry (2007), 28 (1), 344-361CODEN: JCCHDD; ISSN:0192-8651. (John Wiley & Sons, Inc.)
    B3LYP/6-311+G** (and MP2/6-311+G**) computations, performed for a series of Diels-Alder (DA) reactions, confirm that the endo transition states (TS) and the related Cope-TSs are favored energetically over the resp. exo-TSs. Likewise, the computed magnetic properties (nucleus-independent chem. shifts and magnetic susceptibilities) of the endo- (as well as the Cope) TS's reveal their greater electron delocalization and greater aromaticity than the exo-TS's. However, Woodward and Hoffmann's original example is an exception: their endo-TS model, involving the DA reaction of a syn- with an anti-butadiene (BD), actually is disfavored energetically over the corresponding exo-TS; magnetic criteria also do not indicate the existence of SOI delocalization in either case. Instead, a strong energetic preference for endo-TSs due to SOI is found when both BDs are in the syn conformations. This is in accord with Alder and Stein's rule of "max. accumulation of double bonds:" both the dienophile and the diene should have syn conformations. Plots along the IRC's show that the magnetic properties typically are most strongly exalted close to the energetic TS. Because of SOI, all the points along the endo reaction coordinates are more diatropic than along the corresponding exo pathways. We find weak SOI effects to be operative in the endo-TSs involved in the cycloaddns. of cyclic alkenes, cyclopropene, aziridine, cyclobutene, and cyclopentene, with cyclopentadiene. While the endo-TSs are only slightly lower in energy than the resp. exo-TSs, the magnetic properties of the endo-TS's are significantly exalted over those for the exo-TS's and the Natural Bond Orbitals indicate small stabilizing interactions between the methylene cycloalkene hydrogen orbitals (and lone pairs in case of aziridine) with π-character and the diene π MOs.
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  47. 47
    (a) Arabi, A. A.; Matta, C. F. Effects of external electric fields on double proton transfer kinetics in the formic acid dimer. Phys. Chem. Chem. Phys. 2011, 13, 13738– 13748,  DOI: 10.1039/c1cp20175a
    Google Scholar
    47a
    Effects of external electric fields on double proton transfer kinetics in the formic acid dimer
    Arabi, Alya A.; Matta, Cherif F.
    Physical Chemistry Chemical Physics (2011), 13 (30), 13738-13748CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    Mols. can be exposed to strong local elec. fields of the order of 108-1010 V m-1 in the biol. milieu. The effects of such fields on the rate const. (k) of a model reaction, the double-proton transfer reaction in the formic acid dimer (FAD), are investigated. The barrier heights and shapes are calcd. in the absence and presence of several static homogeneous external fields ranging from 5.14 × 108 to 5.14 × 109 V m-1 using d. functional theory (DFT/B3LYP) and second order Moller-Plesset perturbation theory (MP2) in conjunction with the 6-311++G(d,p) Pople basis set. Conventional transition state theory (CTST) followed by Wigner tunneling correction is then applied to est. the rate consts. at 25 °C. It is found that elec. fields parallel to the long axis of the dimer (the line joining the two carbon atoms) lower the uncorrected barrier height, and hence increase the raw k. These fields also flatten the potential energy surface near the transition state region and, hence, decrease the multiplicative tunneling correction factor. The net result of these two opposing effects is that fields increase k(cor.) by a factor of ca. 3-4 (DFT-MP2, resp.) compared to the field-free k. Field strengths of ∼3 × 109 V m-1 are found to be sufficient to double the tunneling-cor. double proton transfer rate const. at 25 °C. Field strengths of similar orders of magnitudes are encountered in the scanning tunneling microscope (STM), in the microenvironment of a DNA base-pair, in an enzyme active site, and in intense laser radiation fields. It is shown that the net (tunneling cor.) effect of the field on k can be closely fitted to an exponential relationship of the form k = aexp(bE), where a and b are consts. and E the elec. field strength.
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    (b) Sowlati-Hashjin, S.; Matta, C. F. The chemical bond in external electric fields: Energies, geometries, and vibrational Stark shifts of diatomic molecules. J. Chem. Phys. 2013, 139, 144101  DOI: 10.1063/1.4820487
    Google Scholar
    47b
    The chemical bond in external electric fields: Energies, geometries, and vibrational Stark shifts of diatomic molecules
    Sowlati-Hashjin, Shahin; Matta, Cherif F.
    Journal of Chemical Physics (2013), 139 (14), 144101/1-144101/14CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    It is shown that the response of mol. properties of diatomics such as the total energy, the bond length, and the vibrational Stark shift to an external homogeneous elec. field (EF) can be predicted from field-free observable properties such as the equil. bond length, the bond dissocn. energy, the polarizability and dipole moment functions, and the vibrational frequency. suggested to approx. the potential energy surface under an EF by a Morse function augmented with a EF term proportional to the internuclear sepn. In this work, this term is replaced by the expression of the field-induced energy change which yields a field-perturbed Morse potential that tends to a const. asymptotic limit when the EF term itself become proportional to the sum of the polarizabilities of the sepd. atoms. The model is validated by comparison with direct calcns. on nine diatomics, five homo-nuclear (H2, N2, O2, F2, and Cl2) and four hetero-nuclear (HF, HCl, CO, and NO), covering a range and combinations of dipole moments and polarizabilities. Calcns. were conducted at the quadratic CI with single and double excitations (QCISD) and d. functional theory (DFT)-B3LYP levels of theory using the 6-311++G(3df,2pd) basis set. All results agree closely at the two levels of theory except for the Stark effect of NO which is not correctly predicted by QCISD calcns. as further calcns., including at the coupled cluster with single and double excitation (CCSD) level of theory, demonstrate. (c) 2013 American Institute of Physics.
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    (c) Sowlati-Hashjin, S.; Karttunen, M.; Matta, C. F. Manipulation of Diatomic Molecules with Oriented External Electric Fields: Linear Correlations in Atomic Properties Lead to Nonlinear Molecular Responses. J. Phys. Chem. A 2020, 124, 4720– 4731,  DOI: 10.1021/acs.jpca.0c02569
    Google Scholar
    47c
    Manipulation of Diatomic Molecules with Oriented External Electric Fields: Linear Correlations in Atomic Properties Lead to Nonlinear Molecular Responses
    Sowlati-Hashjin, Shahin; Karttunen, Mikko; Matta, Cherif F.
    Journal of Physical Chemistry A (2020), 124 (23), 4720-4731CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
    "Oriented external elec. fields (OEEFs)" have been shown to have great potential in being able to provide unprecedented control of chem. reactions, catalysis and selectivity with applications ranging from H2 storage to mol. machines. We report a theor. study of the at. origins of mol. changes due to OEEFs; understanding the characteristics of OEEF-induced couplings between at. and mol. properties is an important step toward comprehensive understanding of the effects of strong external on mol. structure, stability, and reactivity. We focus on the at. and mol. (bond) properties of a set of homo- (H2, N2, O2, F2, and Cl2) and hetero-diat. (HF, HCl, CO, and NO) mols. under intense external elec. fields in the context of quantum theory of atoms in mols. (QTAIM). It is shown that at. properties (at. charges and energies, and localization index) correlate linearly with the field strengths, but mol. properties (bond length, electron d. at bond crit. point, bond length, and electron delocalization index) exhibit non-linear responses to the imposed fields. In particular, the changes in the electron d. distribution alter the shapes and locations of the zero-flux surfaces, at. vols., at. electron population, and localization/delocalization indexes. At the mol. level, the topog. and topol. of the mol. electrostatic potential undergo dramatic changes. The external fields also perturb the covalent-polar-ionic characteristic of the studied chem. bonds, hallmarking the impact of elec. fields on the stability and reactivity of chem. compds. The findings are well-rationalized within the framework of the quantum theory of atoms in mols. and form a coherent conceptual understanding of these effects in prototypical mols. such as diatomics.
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  48. 48
    (a) Bell, R. P. The Theory of Reactions Involving Proton Transfers. Proc. R. Soc. London, Ser. A 1936, 154, 414– 429,  DOI: 10.1098/rspa.1936.0060
    Google Scholar
    There is no corresponding record for this reference.
    (b) Evans, M. G.; Polanyi, M. On the Introduction of Thermodynamic Variables into Reaction Kinetics. Trans. Faraday Soc. 1937, 33, 448– 452,  DOI: 10.1039/tf9373300448
    Google Scholar
    48b
    The introduction of thermodynamic variables into reaction kinetics
    Evans, M. G.; Polanyi, M.
    Transactions of the Faraday Society (1937), 33 (), 448-52CODEN: TFSOA4; ISSN:0014-7672.
    Elucidation of earlier papers by E. and P. (C. A. 29, 6491.3; 31, 309.5) and discussion of points developed by Moelwyn-Hughes (C. A. 31, 2074.4) and Wynne-Jones and Eyring (C. A. 29, 6491.2).
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  49. 49
    (a) Osuna, S.; Morera, J.; Cases, M.; Morokuma, K.; Solà, M. Diels–Alder Reaction between Cyclopentadiene and C60: An Analysis of the Performance of the ONIOM Method for the Study of Chemical Reactivity in Fullerenes and Nanotubes. J. Phys. Chem. A 2009, 113, 9721– 9726,  DOI: 10.1021/jp904294y
    Google Scholar
    49a
    Diels-Alder Reaction between Cyclopentadiene and C60: An Analysis of the Performance of the ONIOM Method for the Study of Chemical Reactivity in Fullerenes and Nanotubes
    Osuna, Silvia; Morera, Josep; Cases, Montserrat; Morokuma, Keiji; Sola, Miquel
    Journal of Physical Chemistry A (2009), 113 (35), 9721-9726CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
    In this article, we theor. analyze the Diels-Alder cycloaddn. between cyclopentadiene and C60 for which exptl. results on energy barriers and reaction energies are known. The comparison of the results obtained with the two-layered ONIOM approach using different partitions for the high- and low-level layers with those obtained employing the B3LYP/6-31G(d) method for the entire system allows us to conclude that the partition including a pyracylene unit of C60 in the description of the high-level layer is enough to get excellent results. Using this partition in the two-layered ONIOM approach, we have computed the energy barriers and reaction energies for this Diels-Alder reaction for different functionals, and we have compared them with exptl. data. From this comparison, both the ONIOM2(M06-2X/6-31G(d):SVWN/STO-3G) and the M06-2X/6-31G(d)//ONIOM2(B3LYP/6-31G(d):SVWN/STO-3G) methods are recommended as reliable and computationally affordable approaches to be exploited for the study of the chem. reactivity of [6,6]-bonds in fullerenes and nanotubes.
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    (b) Osuna, S.; Swart, M.; Solà, M. Dispersion Corrections Essential for the Study of Chemical Reactivity in Fullerenes. J. Phys. Chem. A 2011, 115, 3491– 3496,  DOI: 10.1021/jp1091575
    Google Scholar
    49b
    Dispersion Corrections Essential for the Study of Chemical Reactivity in Fullerenes
    Osuna, Silvia; Swart, Marcel; Sola, Miquel
    Journal of Physical Chemistry A (2011), 115 (15), 3491-3496CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
    In a previous paper, we analyzed theor. the Diels-Alder cycloaddn. between cyclopentadiene and C60 for which exptl. results on energy barriers and reaction energies are known. One of the main conclusions reached was that the two-layered ONIOM2(B3LYP/6-31G(d):SVWN/STO-3G) method provides results very close to the full B3LYP/6-31G(d) ones. Unfortunately, however, both the exothermicity of the reaction and the energy barrier were clearly overestimated by these two methods. In the present work, we analyze the effect of the inclusion of Grimme's dispersion corrections in the energy profile of this reaction. Our results show that these corrections are essential to get results close to the exptl. values. In addn., we have performed calcns. both with and without dispersion corrections for the Diels-Alder reaction of C60 and several dienes and for the Diels-Alder cycloaddn. of a (5,5) single-walled carbon nanotube and 1,3-cis-butadiene. The results obtained indicate that inclusion of dispersion corrections is compulsory for the study of the chem. reactivity of fullerenes and nanotubes.
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    (c) Fernández, I.; Solà, M.; Bickelhaupt, F. M. Why Do Cycloaddition Reactions Involving C60 Prefer [6,6] over [5,6] Bonds?. Chem.─Eur. J. 2013, 19, 7416– 7422,  DOI: 10.1002/chem.201300648
    Google Scholar
    49c
    Why Do Cycloaddition Reactions Involving C60 Prefer [6,6] over [5,6] Bonds?
    Fernandez, Israel; Sola, Miquel; Bickelhaupt, F. Matthias
    Chemistry - A European Journal (2013), 19 (23), 7416-7422CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The origin of the exptl. known preference for [6,6] over [5,6] bonds in cycloaddn. reactions involving C60 has been computationally explored. To this end, the Diels-Alder reaction between cyclopentadiene and C60 has been analyzed by means of the recently introduced activation strain model of reactivity in combination with the energy decompn. anal. method. Other issues, such as the aromaticity of the corresponding transition states, have also been considered. These results indicate that the major factor controlling the obsd. regioselectivity is the more stabilizing interaction between the deformed reactants in the [6,6] reaction pathway along the entire reaction coordinate.
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  50. 50
    Pang, L. S. K.; Wilson, M. A. Reactions of Fullerenes C60 and C70 with Cyclopentadiene. J. Phys. Chem. C. 1993, 97, 6761– 6763,  DOI: 10.1021/j100128a001
    Google Scholar
    There is no corresponding record for this reference.
  51. 51
    Garcia-Borràs, M.; Osuna, S.; Swart, M.; Luis, J. M.; Solà, M. Electrochemical Control of the Regioselectivity in the Exohedral Functionalization of C60: the Role of Aromaticity. Chem. Commun. 2013, 49, 1220– 1222,  DOI: 10.1039/c2cc38390j
    Google Scholar
    51
    Electrochemical control of the regioselectivity in the exohedral functionalization of C60: the role of aromaticity
    Garcia-Borras, Marc; Osuna, Silvia; Swart, Marcel; Luis, Josep M.; Sola, Miquel
    Chemical Communications (Cambridge, United Kingdom) (2013), 49 (12), 1220-1222CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    In this work we show that the regioselectivity of the Diels-Alder, 1,3-dipolar, and carbene cycloaddns. to C60 changes from the usual [6,6] addn. in neutral species to the [5,6] attack when the no. of electrons added to the fullerenic cage increases. Changes in the aromaticity of the five- and six-membered rings of C60 during the redn. process provide a rationale to understand this regioselectivity change.
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  52. 52
    El Bakouri, O.; Garcia-Borràs, M.; Girón, R. M.; Filippone, S.; Martín, N.; Solà, M. On the Regioselectivity of the Diels–Alder Cycloaddition to C60 in High Spin States. Phys. Chem. Chem. Phys. 2018, 20, 11577– 11585,  DOI: 10.1039/C7CP07965F
    Google Scholar
    52
    On the regioselectivity of the Diels-Alder cycloaddition to C60 in high spin states
    El Bakouri, Ouissam; Garcia-Borras, Marc; Giron, Rosa M.; Filippone, Salvatore; Martin, Nazario; Sola, Miquel
    Physical Chemistry Chemical Physics (2018), 20 (17), 11577-11585CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    Controlling the regioselectivity in the exohedral functionalization of fullerenes and endohedral metallofullerenes is essential to produce specific desired fullerene derivs. In this work, using d. functional theory (DFT) calcns., we show that the regioselectivity of the Diels-Alder (DA) cycloaddn. of cyclopentadiene to 2S+1C60 changes from the usual [6,6] addn. in the singlet ground state to the [5,6] attack in high spin states of C60. Changes in the aromaticity of the five- and six-membered rings when going from singlet to high spin C60 provide a rationale to understand this regioselectivity change. Exptl., however, we find that the DA cycloaddn. of isoindene to triplet C60 yields the usual [6,6] adduct. Further DFT calcns. and computational anal. give an explanation to this unanticipated exptl. result by showing the presence of an intersystem crossing close to the formed triplet biradical intermediate.
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  • Abstract

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    Scheme 1

    Scheme 1. Studied (3 + 2) Cycloaddition Reaction between Azomethine Ylide and Nitrostyrene with the Four Possible Cycloadducts
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    Figure 1

    Figure 1. Activation energy barriers for the (3 + 2) cycloaddition between azomethine ylide and nitrostyrene (kcal·mol–1) in terms of the applied EEF z-axis. Dashed lines represent the prediction using FDBβ. Solid lines correspond to the explicit optimization of the reactants, products, and TSs in the presence of an EEF. Calculations were performed at the B3LYP-D3BJ/6-311+G(2d,2p)//B3LYP-D3BJ/6-31+G(d,p) level of theory.

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    Figure 2

    Figure 2. Activation energy barriers for the (3 + 2) cycloaddition between azomethine ylide and nitrostyrene (kcal·mol–1) in terms of the applied EEF y-axis. See Figure 1 caption for additional details.

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    Figure 3

    Figure 3. Activation energy barriers for the (3 + 2) cycloaddition between azomethine ylide and nitrostyrene (kcal·mol–1) for the exo cycloadduct in terms of y-axis EEF. Dotted and dashed lines represent several levels of truncation of eq 4. See Figure 1 caption for additional details.

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    Scheme 2

    Scheme 2. Studied DA Reaction between Maleic Anhydride and Cyclopentadiene
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    Figure 4

    Figure 4. Activation energy barriers for the endo and exo DA pathways between maleic anhydride and cyclopentadiene (kcal·mol–1) in terms of z-axis EEF. Calculations performed at the B3LYP/6-311++G(d,p)//BP86/6-31+G(d) level of theory. See Figure 1 caption for additional details.

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    Figure 5

    Figure 5. Activation energy barriers for the endo and exo DA cycloaddition between maleic anhydride and cyclopentadiene (kcal·mol–1) in terms of y-axis EEF. See Figure 4 caption for additional details.

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    Figure 6

    Figure 6. Two-dimensional representation of the chemical barriers for the major kinetic product of the DA reaction between maleic anhydride and cyclopentadiene in terms of EEFs along the y and z-axes using the FDBβ approach. Green and red zones indicate exo and endo kinetic selectivities, respectively. Calculations are performed at the B3LYP/6-311++G(d,p)//BP86/6-31+G(d) level of theory. Isoenergy barrier lines in kcal·mol–1.

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    Scheme 3

    Scheme 3. Studied 1,3-Dipolar Cycloaddition between Phenyl Diazomethane and Methoxyethene and the Four Possible Cycloadducts; Definition of the Cartesian Coordinates for the Reaction
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    Figure 7

    Figure 7. Activation energy barriers for (3 + 2) dipolar reactions between phenyl diazomethane and methoxyethene (kcal·mol–1) in terms of the applied x-axis EEF. See Figure 1 caption for additional details.

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    Figure 8

    Figure 8. Activation energy barriers for the (3 + 2) dipolar reaction between phenyl diazomethane and methoxyethene (kcal·mol–1) in terms of the applied y-axis EEF. See Figure 1 caption for additional details.

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    Figure 9

    Figure 9. Two-dimensional representation of the activation energy barriers for the major kinetic product of the (3 + 2) dipolar reaction between phenyl diazomethane and methoxyethene in terms of the applied EEFs along the x- and y-axes using the FDBβ approach. Green, red, blue, and orange zones indicate exo, endo, exo′, and endo′ kinetic selectivities, respectively. Black dots indicate the MEFISS points. Calculations are performed at the B3LYP-D3BJ/6-311+G(2d,2p)//B3LYP-D3BJ/6-31+G(d,p) level of theory. Isoenergy barrier lines in kcal·mol–1.

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    Scheme 4

    Scheme 4. Schematic Representation of DA Reaction over a [6,6]- (Top) or [5,6]-Bond (Bottom) of a C60 Fullerene Represented by One of Its Corannulene Unit, Respectively
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    Figure 10

    Figure 10. Activation energy barriers of the DA between C60 and cyclopentadiene (kcal·mol–1) in terms of the applied z-axis EEF. Solid lines are calculated at the B3LYP-D3BJ/6-311+G(2d,2p)//B3LYP-D3BJ/6-31+G(d,p) level of theory using the FDBβ approximation. Color dots correspond to explicit field-dependent geometrical optimizations performed for a specific EEF.

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  • References

    This article references 52 other publications.

    1. 1
      (a) Shaik, S.; Mandal, D.; Ramanan, R. Oriented Electric Fields as Future Smart Reagents in Chemistry. Nat. Chem. 2016, 8, 1091– 1098,  DOI: 10.1038/nchem.2651
      1a
      Oriented electric fields as future smart reagents in chemistry
      Shaik, Sason; Mandal, Debasish; Ramanan, Rajeev
      Nature Chemistry (2016), 8 (12), 1091-1098CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)
      A review. Oriented external elec. fields (OEEFs) as smart reagents are no longer a theor. dream. Here, the wide-ranging potential of using OEEFs to catalyze and control a variety of nonredox reactions and impart selectivity at will are discussed. An OEEF along the direction of electron reorganization (the so-called reaction axis) will catalyze nonpolar reactions by orders of magnitude, control regioselectivity and induce spin-state selectivity. Simply flipping the direction of the OEEF or orienting it off of the reaction axis, will control at will the endo/exo ratio in Diels-Alder reactions and steps in enzymic cycles. This Perspective highlights these outcomes using theor. results for hydrogen abstraction reactions, epoxidn. of double bonds, C-C bond forming reactions, proton transfers and the cycle of the enzyme cytochrome P 450, as well as recent exptl. data. The authors postulate that, as exptl. techniques mature, chem. syntheses may become an exercise in zapping oriented mols. with OEEFs.
      >> More from SciFinder ®
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      (b) Che, F.; Gray, J. T.; Ha, S.; Kruse, N.; Scott, S. L.; McEwen, J.-S. Elucidating the Roles of Electric Fields in Catalysis: A Perspective. ACS Catal. 2018, 8, 5153– 5174,  DOI: 10.1021/acscatal.7b02899
      1b
      Elucidating the Roles of Electric Fields in Catalysis: A Perspective
      Che, Fanglin; Gray, Jake T.; Ha, Su; Kruse, Norbert; Scott, Susannah L.; McEwen, Jean-Sabin
      ACS Catalysis (2018), 8 (6), 5153-5174CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      A review. This Perspective illustrates how the presence of internal and external elec. fields can affect catalytic activity and selectivity, with a focus on heterogeneous catalysts. Specifically, exptl. studies of the elec. field influence on catalyst selectivity in pulsed field mass desorption microscopes, scanning tunneling microscopes, probe-bed-probe reactors, continuous-circuit reactors, and capacitor reactors are described. Through these examples, the elec. field, whether externally applied or intrinsically present, can affect the behavior of a wide no. of materials relevant to catalysis. The authors review some of the theor. methods that were used to elucidate the influence of external elec. fields on catalytic reactions, as well as the application of such methods to selective methane activation. In doing so, the authors illustrate the breadth of possibilities in field-assisted catalysis.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXmslGqsb4%253D&md5=e73298ae055cc34207b58f59a4c535f3
      (c) Shaik, S.; Ramanan, R.; Danovich, D.; Mandal, D. Structure and Reactivity/Selectivity Control by Oriented-External Electric Fields. Chem. Soc. Rev. 2018, 47, 5125– 5145,  DOI: 10.1039/C8CS00354H
      1c
      Structure and reactivity/selectivity control by oriented-external electric fields
      Shaik, Sason; Ramanan, Rajeev; Danovich, David; Mandal, Debasish
      Chemical Society Reviews (2018), 47 (14), 5125-5145CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      This is a tutorial on use of external-elec.-fields (EEFs) as effectors of chem. change. The tutorial instructs readers how to conceptualize and design elec.-field effects on bonds, structures, and reactions. Most effects can be comprehended as the field-induced stabilization of ionic structures. Thus, orienting the field along the "bond axis" will facilitate bond breaking. Similarly, orienting the field along the "reaction axis", the direction in which "electron pairs transform" from reactants- to products-like, will catalyze the reaction. Flipping the field's orientation along the reaction-axis will cause inhibition. Orienting the field off-reaction-axis will control stereo-selectivity and remove forbidden-orbital mixing. Two-directional fields may control both reactivity and selectivity. Increasing the field strength for concerted reactions (e.g., Diels-Alder's) will cause mechanistic-switchover to stepwise mechanisms with ionic intermediates. Examples of bond breaking and control of reactivity/selectivity and mechanisms are presented and analyzed from the "ionic perspective". The tutorial projects the unity of EEF effects, "giving insight and nos.".
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXht1OjtL3K&md5=f56f13e624805dfb6d36b7951fd1a008
      (d) Robertson, J. C.; Coote, M. L.; Bissember, A. C. Synthetic Applications of Light, Electricity, Mechanical Force and Flow. Nat. Rev. Chem. 2019, 3, 290– 304,  DOI: 10.1038/s41570-019-0094-2
      There is no corresponding record for this reference.
      (e) Shaik, S.; Danovich, D.; Joy, J.; Wang, Z.; Stuyver, T. Electric-Field Mediated Chemistry: Uncovering and Exploiting the Potential of (Oriented) Electric Fields to Exert Chemical Catalysis and Reaction Control. J. Am. Chem. Soc. 2020, 142, 12551– 12562,  DOI: 10.1021/jacs.0c05128
      1e
      Electric-Field Mediated Chemistry: Uncovering and Exploiting the Potential of (Oriented) Electric Fields to Exert Chemical Catalysis and Reaction Control
      Shaik, Sason; Danovich, David; Joy, Jyothish; Wang, Zhanfeng; Stuyver, Thijs
      Journal of the American Chemical Society (2020), 142 (29), 12551-12562CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      A review. This Perspective discusses oriented external-elec.-fields (OEEF), and other elec.-field types, as "smart reagents", which enable in principle control over wide-ranging aspects of reactivity and structure. We discuss the potential of OEEFs to control nonredox reactions and impart rate-enhancement and selectivity. An OEEF along the "reaction axis", which is the direction whereby electronic reorganization converts reactants' to products' bonding, will accelerate reactions, control regioselectivity, induce spin-state selectivity, and elicit mechanistic crossovers. Simply flipping the direction of the OEEF will lead to inhibition. Orienting the OEEF off the reaction axis enables control over stereoselectivity, enantioselectivity, and product selectivity. For polar/polarizable reactants, the OEEF itself will act as tweezers, which orient the reactants and drive their reaction. OEEFs also affect bond-dissocn. energies and dissocn. modes (covalent vs ionic), as well as alteration of mol. geometries and supramol. aggregation. The "key" to gaining access to this toolbox provided by OEEFs is microscopic control over the alignment between the mol. and the applied field. We discuss the elegant exptl. methods which have been used to verify the theor. predictions and describe various alternative EEF sources and prospects for upscaling OEEF catalysis in solvents. We also demonstrate the numerous ways in which the OEEF effects can be mimicked by use of (designed) local-elec. fields (LEFs), i.e., by embedding charges or dipoles into mols. LEFs and OEEFs are shown to be equiv. and to obey the same ground rules. Outcomes are exemplified for Diels-Alder cycloaddns., oxidative addn. of bonds by transition-metal complexes, H-abstractions by oxo-metal species, ionic cleavage of halogen bonds, methane activation, etc.
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      (f) Léonard, N. G.; Dhaoui, R.; Chantarojsiri, T.; Yang, J. Y. Electric Fields in Catalysis: From Enzymes to Molecular Catalysts. ACS Catal. 2021, 10923– 10932,  DOI: 10.1021/acscatal.1c02084
      1f
      Electric Fields in Catalysis: From Enzymes to Molecular Catalysts
      Leonard, Nadia G.; Dhaoui, Rakia; Chantarojsiri, Teera; Yang, Jenny Y.
      ACS Catalysis (2021), 11 (17), 10923-10932CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      A review. Elec. fields underlie all reactions and impact reactivity by interacting with the dipoles and net charges of transition states, products, and reactants to modify the free energy landscape. However, they are rarely given deliberate consideration in synthetic design to rationally control reactivity. This Perspective discusses the commonalities of elec. field effects across multiple platforms, from enzymes to mol. catalysts, and identifies practical challenges to applying them in synthetic mol. systems to mediate reactivity.
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    2. 2
      (a) Bhattacharyya, D.; Videla, P. E.; Cattaneo, M.; Batista, V. S.; Lian, T.; Kubiak, C. P. Vibrational Stark Shift Spectroscopy of Catalysts under the Influence of Electric Fields at Electrode–Solution Interfaces. Chem. Sci. 2021, 12, 10131– 10149,  DOI: 10.1039/D1SC01876K
      2a
      Vibrational Stark shift spectroscopy of catalysts under the influence of electric fields at electrode-solution interfaces
      Bhattacharyya, Dhritiman; Videla, Pablo E.; Cattaneo, Mauricio; Batista, Victor S.; Lian, Tianquan; Kubiak, Clifford P.
      Chemical Science (2021), 12 (30), 10131-10149CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
      A review. External control of chem. processes is a subject of widespread interest in chem. research, including control of electrocatalytic processes with significant promise in energy research. The electrochem. double-layer is the nanoscale region next to the electrode/electrolyte interface where chem. reactions typically occur. Understanding the effects of elec. fields within the electrochem. double layer requires a combination of synthesis, electrochem., spectroscopy, and theory. In particular, vibrational sum frequency generation (VSFG) spectroscopy is a powerful technique to probe the response of mol. catalysts at the electrode interface under bias. Fundamental understanding can be obtained via synthetic tuning of the adsorbed mol. catalysts on the electrode surface and by combining exptl. VSFG data with theor. modeling of the Stark shift response. The resulting insights at the mol. level are particularly valuable for the development of new methodologies to control and characterize catalysts confined to electrode surfaces. This Perspective article is focused on how systematic modifications of mols. anchored to surfaces report information concerning the geometric, energetic, and electronic parameters of catalysts under bias attached to electrode surfaces.
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      (b) Concellón, A.; Lu, R.-Q.; Yoshinaga, K.; Hsu, H.-F.; Swager, T. M. Electric-Field-Induced Chirality in Columnar Liquid Crystals. J. Am. Chem. Soc. 2021, 143, 9260– 9266,  DOI: 10.1021/jacs.1c05268
      2b
      Electric-Field-Induced Chirality in Columnar Liquid Crystals
      Concellon, Alberto; Lu, Ru-Qiang; Yoshinaga, Kosuke; Hsu, Hsiu-Fu; Swager, Timothy M.
      Journal of the American Chemical Society (2021), 143 (24), 9260-9266CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      We describe a novel class of tetraphenylbenzene-based discotic mols. with exceptional self-assembling properties. Absorption and fluorescence studies confirmed the formation of J-type aggregates in soln. The discotic mesogens also show an enhancement of the emission upon aggregation. Interestingly, these discotic mols. displayed enantiotropic hexagonal columnar liq. crystal (LC) phases that can be switched into a helical columnar organization by application of an elec. field. The helical columns arise from the elec.-field-induced tilt of the polar fluorobenzene ring that directs all of the peripheral Ph groups into a propeller-like conformation with respect to the central benzene core. A cooperative assembly process of these propeller-shaped mols. resolves into a helical columnar organization, in which the preferred helical sense is obtained from the stereogenic center proximate to the polar carbon-fluorine bond. The ease of inducing chirality in columnar LCs by an elec. field presents opportunities to create next-generation chiral materials for a variety of applications.
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      (c) Kawasaki, T.; Kaimori, Y.; Shimada, S.; Hara, N.; Sato, S.; Suzuki, K.; Asahi, T.; Matsumoto, A.; Soai, K. Asymmetric Autocatalysis Triggered by Triglycine Sulfate with Switchable Chirality by Altering the Direction of the Applied Electric Field. Chem. Commun. 2021, 57, 5999– 6002,  DOI: 10.1039/D1CC02162A
      2c
      Asymmetric autocatalysis triggered by triglycine sulfate with switchable chirality by altering the direction of the applied electric field
      Kawasaki, Tsuneomi; Kaimori, Yoshiyasu; Shimada, Seiya; Hara, Natsuki; Sato, Susumu; Suzuki, Kenta; Asahi, Toru; Matsumoto, Arimasa; Soai, Kenso
      Chemical Communications (Cambridge, United Kingdom) (2021), 57 (49), 5999-6002CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      Triglycine sulfate (TGS) acts as a chiral trigger for asym. autocatalysis with amplification of enantiomeric excess, i.e., the Soai reaction. Therefore, mol. chirality of highly enantioenriched org. compds. is controlled by a ferroelec. crystal TGS, whose polarization is altered by an elec. field.
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      (d) Nakamura, K.; Sugiura, S.; Araoka, F.; Aya, S.; Takanishi, Y.; Watanabe, G.; Sato, R.; Shigeta, Y.; Maeda, H. Conformation-Changeable π-Electronic Systems with Metastable Bent-Core Conformations and Liquid-Crystalline-State Electric-Field-Responsive Properties. Org. Lett. 2021, 23, 305– 310,  DOI: 10.1021/acs.orglett.0c03791
      2d
      Conformation-Changeable π-Electronic Systems with Metastable Bent-Core Conformations and Liquid-Crystalline-State Electric-Field-Responsive Properties
      Nakamura, Kazuto; Sugiura, Shinya; Araoka, Fumito; Aya, Satoshi; Takanishi, Yoichi; Watanabe, Go; Sato, Ryuma; Shigeta, Yasuteru; Maeda, Hiromitsu
      Organic Letters (2021), 23 (2), 305-310CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
      This study focused on the use of nonconventional bent-core π-electronic systems, 2,2'-bipyrroles substituted with modified benzoyl units, as building units of stimuli-responsive assemblies. Elec.-field-responsive mesophase behaviors were obsd. in homochiral synclinic ferroelec. smectic C structures comprising the syn conformations. Elec.-field application induced changes in the polarized optical microscopy textures with dynamic behaviors derived from the conversion from twisted to untwisted states.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXisFGmtbvE&md5=eda796c648125f7465058f6726c26d3a
      (e) Yu, Z.; Wang, L.; Mu, X.; Chen, C.-C.; Wu, Y.; Cao, J.; Tang, Y. Intramolecular Electric Field Construction in Metal Phthalocyanine as Dopant-Free Hole Transporting Material for Stable Perovskite Solar Cells with >21% Efficiency. Angew. Chem., Int. Ed. 2021, 60, 6294– 6299,  DOI: 10.1002/anie.202016087
      2e
      Intramolecular Electric Field Construction in Metal Phthalocyanine as Dopant-Free Hole Transporting Material for Stable Perovskite Solar Cells with >21 % Efficiency
      Yu, Zefeng; Wang, Luyao; Mu, Xijiao; Chen, Chun-Chao; Wu, Yiying; Cao, Jing; Tang, Yu
      Angewandte Chemie, International Edition (2021), 60 (12), 6294-6299CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Low cond. and hole mobility in the pristine metal phthalocyanines greatly limit their application in perovskite solar cells (PSCs) as the hole-transporting materials (HTMs). Here, we prep. a Ni phthalocyanine (NiPc) decorated by four methoxyethoxy units as HTMs. In NiPc, the two oxygen atoms in peripheral substituent have a modified effect on the dipole direction, while the central Ni atom contributes more electron to phthalocyanine ring, thus efficiently increasing the intramol. dipole. Calcn. analyses reveal the extd. holes within NiPc are mainly concd. on the phthalocyanine core induced by the intramol. elec. field, and further to be transferred by π-π stacking space channel between NiPc mols. Finally, the best efficiency of PSCs with NiPc as dopant-free HTMs realizes a record value of 21.23 % (certified 21.03 %). The PSCs also exhibit the good moisture, heating and light stabilities. This work provides a novel way to improve the performance of PSCs with free-doped metal phthalocyanines as HTMs.
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    3. 3
      (a) Suydam, I. T.; Snow, C. D.; Pande, V. S.; Boxer, S. G. Electric Fields at the Active Site of an Enzyme: Direct Comparison of Experiment with Theory. Science 2006, 313, 200– 204,  DOI: 10.1126/science.1127159
      3a
      Electric Fields at the Active Site of an Enzyme: Direct Comparison of Experiment with Theory
      Suydam, Ian T.; Snow, Christopher D.; Pande, Vijay S.; Boxer, Steven G.
      Science (Washington, DC, United States) (2006), 313 (5784), 200-204CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
      The elec. fields produced in folded proteins influence nearly every aspect of protein function. We present a vibrational spectroscopy technique that measures changes in elec. field at a specific site of a protein as shifts in frequency (Stark shifts) of a calibrated nitrile vibration. A nitrile-contg. inhibitor is used to deliver a unique probe vibration to the active site of human aldose reductase, and the response of the nitrile stretch frequency is measured for a series of mutations in the enzyme active site. These shifts yield quant. information on elec. fields that can be directly compared with electrostatics calcns. We show that extensive mol. dynamics simulations and ensemble averaging are required to reproduce the obsd. changes in field.
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      (b) Gorin, C. F.; Beh, E. S.; Kanan, M. W. An Electric Field–Induced Change in the Selectivity of a Metal Oxide–Catalyzed Epoxide Rearrangement. J. Am. Chem. Soc. 2012, 134, 186– 189,  DOI: 10.1021/ja210365j
      3b
      An Electric Field-Induced Change in the Selectivity of a Metal Oxide-Catalyzed Epoxide Rearrangement
      Gorin, Craig F.; Beh, Eugene S.; Kanan, Matthew W.
      Journal of the American Chemical Society (2012), 134 (1), 186-189CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      The rearrangement of cis-stilbene oxide catalyzed by Al2O3 was studied in the presence of interfacial elec. fields. Thin films of Al2O3 deposited on Si electrodes were used as the opposing walls of a reaction vessel. Application of a voltage across the electrodes engendered electrochem. double layer formation at the Al2O3-soln. interface. The aldehyde to ketone product ratio of the rearrangement was increased by up to a factor of 63 as the magnitude of the double layer charge d. was increased. The results support a field-dipole effect on the selectivity of the catalytic reaction.
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      (c) Gorin, C. F.; Beh, E. S.; Bui, Q. M.; Dick, G. R.; Kanan, M. W. Interfacial Electric Field Effects on a Carbene Reaction Catalyzed by Rh Porphyrins. J. Am. Chem. Soc. 2013, 135, 11257– 11265,  DOI: 10.1021/ja404394z
      3c
      Interfacial Electric Field Effects on a Carbene Reaction Catalyzed by Rh Porphyrins
      Gorin, Craig F.; Beh, Eugene S.; Bui, Quan M.; Dick, Graham R.; Kanan, Matthew W.
      Journal of the American Chemical Society (2013), 135 (30), 11257-11265CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      An intramol. reaction catalyzed by Rh porphyrins was studied in the presence of interfacial elec. fields. 1-Diazo-3,3-dimethyl-5-phenylhex-5-en-2-one (2) reacts with Rh porphyrins via a putative carbenoid intermediate to form cyclopropanation product 3,3-dimethyl-5-phenylbicyclo[3.1.0]hexan-2-one (3) and insertion product 3,3-dimethyl-2,3-dihydro-[1,1'-biphenyl]-4(1H)-one (4). To study this reaction in the presence of an interfacial elec. field, Si electrodes coated with thin films of insulating dielec. layers were used as the opposing walls of a reaction vessel, and Rh porphyrin catalysts were localized to the dielec.-electrolyte interface. The charge d. was varied at the interface by changing the voltage across the two electrodes. The product ratio was analyzed as a function of the applied voltage and the surface chem. of the dielec. layer. In the absence of an applied voltage, the ratio of 3:4 was ∼10:1. With a TiO2 surface, application of a voltage induced a Rh porphyrin-TiO2 interaction that resulted in an increase in the 3:4 ratio to a max. in which 4 was nearly completely suppressed (>100:1). With an Al2O3 surface or an alkylphosphonate-coated surface, the voltage caused a decrease in the 3:4 ratio, with a max. effect of lowering the ratio to 1:2. The voltage-induced decrease in the 3:4 ratio in the absence of TiO2 was consistent with a field-dipole effect that changed the difference in activation energies for the product-detg. step to favor product 4. Effects were obsd. for porphyrin catalysts localized to the electrode-electrolyte interface either through covalent attachment or surface adsorption, enabling the selectivity to be controlled with unfunctionalized Rh porphyrins. The magnitude of the selectivity change was limited by the max. interfacial charge d. that could be attained before dielec. breakdown.
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      (d) Aragonès, A. C.; Haworth, N. L.; Darwish, N.; Ciampi, S.; Bloomfield, N. J.; Wallace, G. G.; Diez-Perez, I.; Coote, M. L. Electrostatic Catalysis of a Diels–Alder Reaction. Nature 2016, 531, 88– 91,  DOI: 10.1038/nature16989
      3d
      Electrostatic catalysis of a Diels-Alder reaction
      Aragones, Albert C.; Haworth, Naomi L.; Darwish, Nadim; Ciampi, Simone; Bloomfield, Nathaniel J.; Wallace, Gordon G.; Diez-Perez, Ismael; Coote, Michelle L.
      Nature (London, United Kingdom) (2016), 531 (7592), 88-91CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)
      It is often thought that the ability to control reaction rates with an applied elec. potential gradient is unique to redox systems. However, recent theor. studies suggest that oriented elec. fields could affect the outcomes of a range of chem. reactions, regardless of whether a redox system is involved. This possibility arises because many formally covalent species can be stabilized via minor charge-sepd. resonance contributors. When an applied elec. field is aligned in such a way as to electrostatically stabilize one of these minor forms, the degree of resonance increases, resulting in the overall stabilization of the mol. or transition state. This means that it should be possible to manipulate the kinetics and thermodn. of non-redox processes using an external elec. field, as long as the orientation of the approaching reactants with respect to the field stimulus can be controlled. Here, we provide exptl. evidence that the formation of carbon-carbon bonds is accelerated by an elec. field. We have designed a surface model system to probe the Diels-Alder reaction, and coupled it with a scanning tunnelling microscopy break-junction approach. This technique, performed at the single-mol. level, is perfectly suited to deliver an elec.-field stimulus across approaching reactants. We find a fivefold increase in the frequency of formation of single-mol. junctions, resulting from the reaction that occurs when the elec. field is present and aligned so as to favor electron flow from the dienophile to the diene. Our results are qual. consistent with those predicted by quantum-chem. calcns. in a theor. model of this system, and herald a new approach to chem. catalysis.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xjs1emtb4%253D&md5=77ec120490d732c961c028e6933fc879
      (e) Olavarría-Contreras, I. J.; Etcheverry-Berríos, A.; Qian, W.; Gutiérrez-Cerón, C.; Campos-Olguín, A.; Sañudo, E. C.; Duli, D.; Ruiz, E.; Aliaga-Alcalde, N.; Soler, M.; van der Zant, H. S. J. Electric-Field Induced Bistability in Single-Molecule Conductance Measurements for Boron Coordinated Curcuminoid Compounds. Chem. Sci. 2018, 9, 6988– 6996,  DOI: 10.1039/C8SC02337A
      3e
      Electric-field induced bistability in single-molecule conductance measurements for boron coordinated curcuminoid compounds
      Olavarria-Contreras, Ignacio Jose; Etcheverry-Berrios, Alvaro; Qian, Wenjie; Gutierrez-Ceron, Cristian; Campos-Olguin, Aldo; Sanudo, E. Carolina; Dulic, Diana; Ruiz, Eliseo; Aliaga-Alcalde, Nuria; Soler, Monica; van der Zant, Herre S. J.
      Chemical Science (2018), 9 (34), 6988-6996CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
      We have studied the single-mol. conductance of a family of curcuminoid mols. (CCMs) using the mech. controlled break junction (MCBJ) technique. The CCMs under study contain methylthio (MeS-) as anchoring groups: MeS-CCM (1), the free-ligand org. mol., and two coordination compds., MeS-CCM-BF2 (2) and MeS-CCM-Cu (3), where ligand 1 coordinates to a boron center (BF2 group) and to a CuII moiety, resp. We found that the three mols. present stable mol. junctions allowing detailed statistical anal. of their electronic properties. Compd. 3 shows a slight increase in the conductance with respect to free ligand 1, whereas incorporation of BF2 (compd. 2) promotes the presence of two conductance states in the measurements. Addnl. expts. with control mols. point out that this bistability is related to the combination of MeS- anchoring groups and the BF2 moiety within the structure of the mols. Theor. calcns. show that this can be explained by the presence of two conformers once compd. 2 is anchored between the gold electrodes. An energy min. is found for a flat structure but there is a dramatic change in the magnitude and orientation of dipole moment (favoring a non-flat conformer in the presence of an external elec. field) due to a conformational change of one of the terminal MeS- groups. The results thus point to an intricate interplay between the applied bias voltage and the mol. dipole moment which could be the basis for designing new mols. aiming at controlling their conformation in devices.
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      (f) Huang, X.; Tang, C.; Li, J.; Chen, L.-C.; Zheng, J.; Zhang, P.; Le, J.; Li, R.; Li, X.; Liu, J.; Yang, Y.; Shi, J.; Chen, Z.; Bai, M.; Zhang, H.-L.; Xia, H.; Cheng, J.; Tian, Z.-Q.; Hong, W. Electric Field–Induced Selective Catalysis of Single-Molecule Reaction. Sci. Adv. 2019, 5, eaaw3072  DOI: 10.1126/sciadv.aaw3072
      There is no corresponding record for this reference.
      (g) Zang, Y.; Zou, Q.; Fu, T.; Ng, F.; Fowler, B.; Yang, J.; Li, H.; Steigerwald, M. L.; Nuckolls, C.; Venkataraman, L. Directing Isomerization Reactions of Cumulenes with Electric Fields. Nat. Commun. 2019, 10, 4482  DOI: 10.1038/s41467-019-12487-w
      3g
      Directing isomerization reactions of cumulenes with electric fields
      Zang Yaping; Venkataraman Latha; Zou Qi; Fu Tianren; Ng Fay; Fowler Brandon; Yang Jingjing; Steigerwald Michael L; Nuckolls Colin; Venkataraman Latha; Zou Qi; Li Hexing
      Nature communications (2019), 10 (1), 4482 ISSN:.
      Electric fields have been proposed as having a distinct ability to catalyze chemical reactions through the stabilization of polar or ionic intermediate transition states. Although field-assisted catalysis is being researched, the ability to catalyze reactions in solution using electric fields remains elusive and the understanding of mechanisms of such catalysis is sparse. Here we show that an electric field can catalyze the cis-to-trans isomerization of [3]cumulene derivatives in solution, in a scanning tunneling microscope. We further show that the external electric field can alter the thermodynamics inhibiting the trans-to-cis reverse reaction, endowing the selectivity toward trans isomer. Using density functional theory-based calculations, we find that the applied electric field promotes a zwitterionic resonance form, which ensures a lower energy transition state for the isomerization reaction. The field also stabilizes the trans form, relative to the cis, dictating the cis/trans thermodynamics, driving the equilibrium product exclusively toward the trans.
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      (h) Tang, Y.; Zhou, Y.; Zhou, D.; Chen, Y.; Xiao, Z.; Shi, J.; Liu, J.; Hong, W. Electric Field-Induced Assembly in Single-Stacking Terphenyl Junctions. J. Am. Chem. Soc. 2020, 142, 19101– 19109,  DOI: 10.1021/jacs.0c07348
      3h
      Electric Field-Induced Assembly in Single-Stacking Terphenyl Junctions
      Tang, Yongxiang; Zhou, Yu; Zhou, Dahai; Chen, Yaorong; Xiao, Zongyuan; Shi, Jia; Liu, Junyang; Hong, Wenjing
      Journal of the American Chemical Society (2020), 142 (45), 19101-19109CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Mol. assembly is crucial in functional mol. materials and devices. Among the mol. interactions that can form assemblies, stacking among π-conjugated mol. backbones plays an essential role in charge transport through org. materials and devices. The single-mol. junction technique allows for the application of an elec. field of approx. 108 V/m to the nanoscale junctions and to investigate the elec. field-induced assembly at the single-stacking level. Here, we demonstrate an elec. field-induced stacking effect between two mols. using the scanning tunneling microscope break junction (STM-BJ) technique and we found an increase in the stacking probability with increasing intensity of the elec. field. The combined d. functional theory (DFT) calcns. suggest that the mols. become more planar under the elec. field, leading to the energetically preferred stacking configuration. Our study provides a new strategy for tuning mol. assembly by employing a strong elec. field.
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      (i) Gao, T.; Pan, Z.; Cai, Z.; Zheng, J.; Tang, C.; Yuan, S.; Zhao, S. q.; Bai, H.; Yang, Y.; Shi, J.; Xiao, Z.; Liu, J.; Hong, W. Electric Field-Induced Switching among Multiple Conductance Pathways in Single-Molecule Junctions. Chem. Commun. 2021, 57, 7160– 7163,  DOI: 10.1039/D1CC02111G
      3i
      Electric field-induced switching among multiple conductance pathways in single-molecule junctions
      Gao, Tengyang; Pan, Zhichao; Cai, Zhuanyun; Zheng, Jueting; Tang, Chun; Yuan, Saisai; Zhao, Shi qiang; Bai, Hua; Yang, Yang; Shi, Jia; Xiao, Zongyuan; Liu, Junyang; Hong, Wenjing
      Chemical Communications (Cambridge, United Kingdom) (2021), 57 (58), 7160-7163CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      Here, we report the switching among multiple conductance pathways achieved by sliding the scanning tunneling microscope tip among different binding sites under different elec. fields. With an increase in the elec. field, high mol. conductance states appear, suggesting the formation of different configurations in single-mol. junctions. The switch can be operated in situ and reversibly, which is also confirmed by the apparent conductance conversion in I-V measurements. Theor. simulations also agree well with the exptl. results, which implies that the elec. field enables the possibility to trigger switching in single-mol. junctions.
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    4. 4
      Meir, R.; Chen, H.; Lai, W.; Shaik, S. Oriented Electric Fields Accelerate Diels–Alder Reactions and Control the endo/exo Selectivity. ChemPhysChem 2010, 11, 301– 310,  DOI: 10.1002/cphc.200900848
      4
      Oriented Electric Fields Accelerate Diels-Alder Reactions and Control the endo/exo Selectivity
      Meir, Rinat; Chen, Hui; Lai, Wenzhen; Shaik, Sason
      ChemPhysChem (2010), 11 (1), 301-310CODEN: CPCHFT; ISSN:1439-4235. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Herein an external elec. field (EEF) acts as an accessory catalyst/inhibitor for Diels-Alder (DA) reactions. When the EEF is oriented along the reaction axis (the coordinate of approach of the reactants in the reaction path), the barrier of the DA reactions is lowered by a significant amt., equiv. to rate enhancements by 4-6 orders of magnitude. Simply flipping the EEF direction has the opposite effect, and the EEF acts as an inhibitor. Addnl., an EEF oriented perpendicular to the reaction axis in the direction of the individual mol. dipoles can change the endo/exo selectivity, favoring one or the other depending on the pos./neg. directions of the EEF vis-a-vis the individual mol. dipole. At some crit. value of the EEF along the reaction axis, there is a crossover to a stepwise mechanism that involves a zwitterionic intermediate. The valence bond diagram model is used to comprehend these trends and to derive a selection rule for EEF effects on chem. reactions: an EEF aligned in the direction of the electron flow between the reactants will lower the reaction barrier. The exo/endo control by the EEF is not assocd. with changes in secondary orbital interactions.
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    5. 5
      (a) Andrés, J. L.; Lledós, A.; Duran, M.; Bertrán, J. Electric Fields Acting as Catalysts in Chemical Reactions. An ab Initio Study of the Walden Inversion Reaction. Chem. Phys. Lett. 1988, 153, 82– 86,  DOI: 10.1016/0009-2614(88)80136-2
      5a
      Electric fields acting as catalysts in chemical reactions. An ab initio study of the Walden inversion reaction
      Andres, J. L.; Lledos, A.; Duran, M.; Bertran, J.
      Chemical Physics Letters (1988), 153 (1), 82-6CODEN: CHPLBC; ISSN:0009-2614.
      Ab initio SCF calcns. were carried out on the F- exchange reaction F- + CH3F → FCH3 + F-. An external uniform elec. field along the FCF axis was incorporated by proper changes in the 1-electron part of the Fock matrix. The reaction profile is dramatically modified with increase in strength of the applied field. The elec. field is essential to describe the potential energy hypersurface so that it intervenes in the reaction coordinate. Strong elec. fields therefore open a new way to catalyze reactions.
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      (b) Carbonell, E.; Duran, M.; Lledós, A.; Bertrán, J. Catalysis of Friedel-Crafts Reactions by Electric Fields. J. Phys. Chem. A. 1991, 95, 179– 183,  DOI: 10.1021/j100154a036
      5b
      Catalysis of Friedel-Crafts reactions by electric fields
      Carbonell, Emili; Duran, Miquel; Lledos, Agusti; Bertran, Juan
      Journal of Physical Chemistry (1991), 95 (1), 179-83CODEN: JPCHAX; ISSN:0022-3654.
      The effects of uniform and nonuniform elec. fields on the HF + CH4 reaction are examd. by using an ab initio RHF method with the 3-21+G basis set. Barrier heights and positions of stationary points along the reaction coordinate are dramatically altered upon introduction of such elec. fields. The changes are analyzed in terms of modifications in at. charges and variations of electron densities at the main bond crit. points. The elec. fields belong to the reaction coordinate of this chem. process.
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      (c) Bhattacharyya, K.; Karmakar, S.; Datta, A. External electric field control: driving the reactivity of metal-free azide–alkyne click reactions. Phys. Chem. Chem. Phys. 2017, 19, 22482– 22486,  DOI: 10.1039/C7CP04202G
      5c
      External electric field control: driving the reactivity of metal-free azide-alkyne click reactions
      Bhattacharyya, Kalishankar; Karmakar, Sharmistha; Datta, Ayan
      Physical Chemistry Chemical Physics (2017), 19 (33), 22482-22486CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      Recent reports have suggested that an external elec. field (EEF) can assist and even control product selectivity. In this work, we have shown that the barrier for the Huisgen reaction between alkyl (aryl) azide and cyclooctyne(biflurocyclooctyne) is reduced by ∼3-4 kcal mol-1 when an oriented EEF is applied along the reaction axis. As a consequence of their inherently polar transition-states (TSs), a parallel orientation of the EEF results in enhancement of the charge transfer (CT) between the fragments and concomitant increase in the dipole moment along the reaction axes. This leads to an increase in the reaction rate for moderate EEFs in the range of 0.3-0.5 V Å-1. Since highly polar and directional environments are omnipresent in biol. environments, metal-free click reactions can be further accelerated for non-invasive imaging of live-cells. Conceptually, elec. field control appears to be a novel tool (catalyst) to drive, and possibly even tune, the reactivity of org. mols.
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      (d) Gryn’ova, G.; Coote, M. L. Directionality and the Role of Polarization in Electric Field Effects on Radical Stability. Aust. J. Chem. 2017, 70, 367– 372,  DOI: 10.1071/CH16579
      5d
      Directionality and the Role of Polarization in Electric Field Effects on Radical Stability
      Gryn'ova, Ganna; Coote, Michelle L.
      Australian Journal of Chemistry (2017), 70 (4), 367-372CODEN: AJCHAS; ISSN:0004-9425. (CSIRO Publishing)
      Accurate quantum-chem. calcns. are used to analyze the effects of charges on the kinetics and thermodn. of radical reactions, with specific attention given to the origin and directionality of the effects. Conventionally, large effects of the charges are expected to occur in systems with pronounced charge-sepd. resonance contributors. The nature (stabilization or destabilization) and magnitude of these effects thus depend on the orientation of the interacting multipoles. However, we show that a significant component of the stabilizing effects of the external elec. field is largely independent of the orientation of external elec. field (e.g. a charged functional group, a point charge, or an electrode) and occurs even in the absence of any pre-existing charge sepn. This effect arises from polarization of the electron d. of the mol. induced by the elec. field. This polarization effect is greater for highly delocalized species such as resonance-stabilized radicals and transition states of radical reactions. We show that this effect on the stability of such species is preserved in chem. reaction energies, leading to lower bond-dissocn. energies and barrier heights. Finally, our simplified modeling of the diol dehydratase-catalyzed 1,2-hydroxyl shift indicates that such stabilizing polarization is likely to contribute to the catalytic activity of enzymes.
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      (e) Welborn, V. V.; Ruiz Pestana, L.; Head-Gordon, T. Computational Optimization of Electric Fields for Better Catalysis Design. Nat. Catal. 2018, 1, 649– 655,  DOI: 10.1038/s41929-018-0109-2
      There is no corresponding record for this reference.
      (f) Acosta-Silva, C.; Bertran, J.; Branchadell, V.; Oliva, A. Kemp Elimination Reaction Catalyzed by Electric Fields. ChemPhysChem 2020, 21, 295– 306,  DOI: 10.1002/cphc.201901155
      5f
      Kemp Elimination Reaction Catalyzed by Electric Fields
      Acosta-Silva, Carles; Bertran, Joan; Branchadell, Vicenc; Oliva, Antoni
      ChemPhysChem (2020), 21 (4), 295-306CODEN: CPCHFT; ISSN:1439-4235. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The Kemp elimination reaction is the most widely used in the de novo design of new enzymes. The effect of two different kinds of elec. fields in the reactions of acetate as a base with benzisoxazole and 5-nitrobenzisoxazole as substrates have been theor. studied. The effect of the solvent reaction field has been calcd. using the SMD continuum model for several solvents; we have shown that solvents inhibit both reactions, the decrease of the reaction rate being larger as far as the dielec. const. is increased. The diminution of the reaction rate is esp. remarkable between aprotic org. solvents and protic solvents as water, the electrostatic term of the hydrogen bonds being the main factor for the large inhibitory effect of water. The presence of an external elec. field oriented in the direction of the charge transfer (z axis) increases it and, so, the reaction rate. In the reaction of the nitro compd., if the elec. field is oriented in an orthogonal direction (x axis) the charge transfer to the NO2 group is favored and there is a subsequent increase of the reaction rate. However, this increase is smaller than the one produced by the field in the z axis. It is worthwhile mentioning that one of the main effects of external elec. fields of intermediate intensity is the reorientation of the reactants. Finally, the implications of our results in the de novo design of enzymes are discussed.
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      (g) Stuyver, T.; Shaik, S. Resolving Entangled Reactivity Modes through External Electric Fields and Substitution: Application to E2/SN2 Reactions. J. Org. Chem. 2021, 86, 9030– 9039,  DOI: 10.1021/acs.joc.1c01010
      5g
      Resolving Entangled Reactivity Modes through External Electric Fields and Substitution: Application to E2/SN2 Reactions
      Stuyver, Thijs; Shaik, Sason
      Journal of Organic Chemistry (2021), 86 (13), 9030-9039CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)
      In this study, we explore strategies to resolve entangled reactivity modes. More specifically, we consider the competition between SN2 and E2 reaction pathways for alkyl halides and nucleophiles/bases. We first demonstrate that the emergence of an E2-preference is assocd. with an enhancement of the magnitude of the resonance stabilization in the transition-state (TS) region, resulting from the improved mixing of electrostatically stabilized valence bond structures into the TS wavefunction. Subsequently, we show that the TS resonance energy can be tuned selectively and rationally either through the application of an oriented external elec. field directed along the C-C axis of the alkyl halide or through a regular substitution approach of the C-C moiety. We end our study by demonstrating that the insights gained from our anal. enable one to rationalize the main reactivity trends emerging from a recently published large database of competing SN2 and E2 reaction pathways.
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    6. 6
      Hill, N. S.; Coote, M. L. Internal Oriented Electric Fields as a Strategy for Selectively Modifying Photochemical Reactivity. J. Am. Chem. Soc. 2018, 140, 17800– 17804,  DOI: 10.1021/jacs.8b12009
      6
      Internal Oriented Electric Fields as a Strategy for Selectively Modifying Photochemical Reactivity
      Hill, Nicholas S.; Coote, Michelle L.
      Journal of the American Chemical Society (2018), 140 (50), 17800-17804CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Time-dependent d. functional theory calcns. were performed on acetophenone derivs. to explore the possibility of using charged functional groups as internal elec. fields, the orientation of which can be altered to change photochem. behavior at will. Nonconjugated charged groups can significantly alter, by up to -1.44 eV, the stabilities of excited states. Specifically, a nonconjugated neg. charged group in the para position will destabilize the nπ* and stabilize the ππ* transitions, while a pos. charged group will do the opposite. These electrostatic effects can be tuned by moving these substituents into the meta and ortho positions. Through use of acids and bases, these charged groups can be switched on or off with pH, allowing for selective alteration of the energy levels and photochem. reactivity. Solvent effects attenuate the elec. field effect with increasing dielec. permittivity; however electrostatic effects remain significant even in quite polar solvents. Using charged functional groups to deliver the position-dependent electrostatic (de)stabilization effects is therefore a potential route to improving the efficiency of desirable photochem. processes.
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    7. 7
      Jaroš, A.; Bonab, E. F.; Straka, M.; Foroutan-Nejad, C. Fullerene-Based Switching Molecular Diodes Controlled by Oriented External Electric Fields. J. Am. Chem. Soc. 2019, 141, 19644– 19654,  DOI: 10.1021/jacs.9b07215
      7
      Fullerene-Based Switching Molecular Diodes Controlled by Oriented External Electric Fields
      Jaros, Adam; Bonab, Esmaeil Farajpour; Straka, Michal; Foroutan-Nejad, Cina
      Journal of the American Chemical Society (2019), 141 (50), 19644-19654CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Employing multi-scale in silico modeling we propose switching mol. diodes on the basis of endohedral fullerenes (fullerene switching diode, FSD), encapsulated with polar mols. of general type MX (M: metal, X: non-metal) to be used for data storage and processing. Here, we demonstrate for MX@C70 systems that the relative orientation of enclosed MX with respect to a set of electrodes connected to the system can be controlled by application of oriented external elec. field(s). We suggest systems with two- and four-terminal electrodes, in which the source and drain electrodes help the current to pass through the device and help the switching between the conductive states of FSD via applied voltage. The gate electrodes then assist the switching by effectively lowering the energy barrier between local min. via stabilizing the transition state of switching process if the applied voltage between the source and drain is insufficient to switch the MX inside the fullerene. Using non-equil. Green's function combined with d. functional theory (DFT-NEGF) computations, we further show that cond. of the studied MX@C70 systems depends on the relative orientation of MX inside the cage with respect to the electrodes. Therefore, the orientation of the MX inside C70 can be both enforced ("written") and retrieved ("read") by applied voltage. The studied systems thus behave like voltage-sensitive switching mol. diodes, that is a reminiscent of a mol. memristor.
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    8. 8
      Kirshenboim, O.; Frenklah, A.; Kozuch, S. Switch Chemistry at Cryogenic Conditions: Quantum Tunnelling under Electric Fields. Chem. Sci. 2021, 12, 3179– 3187,  DOI: 10.1039/D0SC06295B
      8
      Switch chemistry at cryogenic conditions: quantum tunnelling under electric fields
      Kirshenboim, Omer; Frenklah, Alexander; Kozuch, Sebastian
      Chemical Science (2021), 12 (9), 3179-3187CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
      While the influence of intramol. elec. fields is a known feature in enzymes, the use of oriented external elec. fields (EEF) to enhance or inhibit mol. reactivity is a promising topic still in its infancy. Herein we will explore computationally the effects that EEF can provoke in simple mols. close to the abs. zero, where quantum tunnelling (QT) is the sole mechanistic option. We studied three exemplary systems, each one with different reactivity features and known QT kinetics: π bond-shifting in pentalene, Cope rearrangement in semibullvalene, and cycloreversion of diazabicyclohexadiene. The kinetics of these cases depend both on the field strength and its direction, usually giving subtle but remarkable changes. However, for the cycloreversion, which suffers large changes on the dipole through the reaction, we also obsd. striking results. Between the effects caused by the EEF on the QT we obsd. an inversion of the Arrhenius equation, deactivation of the mol. fluxionality, and stabilization or instantaneous decompn. of the system. All these effects may well be achieved, literally, at the flick of a switch.
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    9. 9
      (a) Lei, Y. K.; Zhang, J.; Zhang, Z.; Gao, Y. Q. Dynamic Electric Field Complicates Chemical Reactions in Solutions. J. Phys. Chem. Lett. 2019, 10, 2991– 2997,  DOI: 10.1021/acs.jpclett.9b01038
      9a
      Dynamic Electric Field Complicates Chemical Reactions in Solutions
      Lei, Yao Kun; Zhang, Jun; Zhang, Zhen; Gao, Yi Qin
      Journal of Physical Chemistry Letters (2019), 10 (11), 2991-2997CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      Chem. reactions can be strongly influenced by an external elec. field (EEF), but because the EEF is often time-dependent and in case it does not adapt quickly enough to the reaction progress, esp. during fast barrier crossing processes, dynamic effects could be important. Here we find that electrostatic interactions can reduce the height of the reaction barrier for a Claissen rearrangement reaction and accelerate the key motions for bonding. Meanwhile, strong electrostatic interactions can modify the barrier into an effective potential well, confining the system into the barrier until solvents adjust themselves to provide an appropriate EEF for charge redistribution. In this case, the otherwise concerted mechanism becomes a stepwise one. Consequently, the motion of solvents modulates the reaction dynamics and leads to heterogeneous reaction paths, even in a seemingly homogeneous aq. soln. In addn., an excessive stabilization of transition state retards the barrier crossing process, making the thermodynamically favorable pathway less favored dynamically.
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      (b) Mattioli, E. J.; Bottoni, A.; Zerbetto, F.; Calvaresi, M. Oriented External Electric Fields Affect Rate and Stereoselectivity of Electrocyclic Reactions. J. Phys. Chem. C 2019, 123, 26370– 26378,  DOI: 10.1021/acs.jpcc.9b07358
      9b
      Oriented External Electric Fields Affect Rate and Stereoselectivity of Electrocyclic Reactions
      Mattioli, Edoardo Jun; Bottoni, Andrea; Zerbetto, Francesco; Calvaresi, Matteo
      Journal of Physical Chemistry C (2019), 123 (43), 26370-26378CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      We carried out a computational investigation at the d. functional theory (M06-2X) level on the effects of oriented external elec. fields (OEEF) on activation barriers and stereochem. output of the thermal ring opening of 3-substituted cyclobutenes (C4H5X) to butadienes. It is well known that with π-electron-donor substituents (X = CH3, NH2), the conrotatory outward rotation is preferred, while with π-electron-acceptor substituents (X = CHO, NO, BH2), the conrotatory inward process becomes favored. In the presence of the OEEF applied along the three axes x, y, and z in either pos. or neg. direction, for both π-donor and π-acceptor substituents, we obsd. either catalysis or inhibition. Both effects were consistent with the change of the induced dipole along the direction of the applied field. An interesting effect was obsd. for X = CHO and NO. The simultaneous catalysis and inhibition of the outward and inward transformation leads to a reversed ratio between outward and inward transformation, with the former being favored (stereochem. inversion). Such effect was not obsd. for X = BH2 (the strongest π-acceptor examd. here). In this case, in the absence of the applied field, the difference between the inward and outward barriers is too large and the simultaneous catalysis and inhibition of the outward and inward transformation is not capable of detg. the stereochem. inversion.
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      (c) Shi, M. W.; Thomas, S. P.; Hathwar, V. R.; Edwards, A. J.; Piltz, R. O.; Jayatilaka, D.; Koutsantonis, G. A.; Overgaard, J.; Nishibori, E.; Iversen, B. B.; Spackman, M. A. Measurement of Electric Fields Experienced by Urea Guest Molecules in the 18-Crown-6/Urea (1:5) Host–Guest Complex: An Experimental Reference Point for Electric-Field-Assisted Catalysis. J. Am. Chem. Soc. 2019, 141, 3965– 3976,  DOI: 10.1021/jacs.8b12927
      9c
      Measurement of Electric Fields Experienced by Urea Guest Molecules in the 18-Crown-6/Urea (1:5) Host-Guest Complex: An Experimental Reference Point for Electric-Field-Assisted Catalysis
      Shi, Ming W.; Thomas, Sajesh P.; Hathwar, Venkatesha R.; Edwards, Alison J.; Piltz, Ross O.; Jayatilaka, Dylan; Koutsantonis, George A.; Overgaard, Jacob; Nishibori, Eiji; Iversen, Bo B.; Spackman, Mark A.
      Journal of the American Chemical Society (2019), 141 (9), 3965-3976CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      High-resoln. synchrotron and neutron single-crystal diffraction data of 18-crown-6/(pentakis)urea measured at 30 K are combined, with the aim of better appreciating the electrostatics assocd. with intermol. interactions in condensed matter. With two 18-crown-6 mols. and five different urea mols. in the crystal, this represents the most ambitious combined X-ray/synchrotron and neutron exptl. charge d. anal. to date on a cocrystal or host-guest system incorporating such a large no. of unique mols. The dipole moments of the five urea guest mols. in the crystal are enhanced considerably compared to values detd. for isolated mols., and 2D maps of the electrostatic potential and elec. field show clearly how the urea mols. are oriented with dipole moments aligned along the elec. field exerted by their mol. neighbors. Exptl. elec. fields in the range of 10-19 GV m-1, obtained for the five different urea environments, corroborate independent measurements of elec. fields in the active sites of enzymes and provide an important exptl. ref. point for recent discussions focused on elec.-field-assisted catalysis.
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      (d) Smolinsky, E. Z. B.; Neubauer, A.; Kumar, A.; Yochelis, S.; Capua, E.; Carmieli, R.; Paltiel, Y.; Naaman, R.; Michaeli, K. Electric Field-Controlled Magnetization in GaAs/AlGaAs Heterostructures–Chiral Organic Molecules Hybrids. J. Phys. Chem. Lett. 2019, 10, 1139– 1145,  DOI: 10.1021/acs.jpclett.9b00092
      9d
      Electric Field-Controlled Magnetization in GaAs/AlGaAs Heterostructures-Chiral Organic Molecules Hybrids
      Smolinsky, Eilam Z. B.; Neubauer, Avner; Kumar, Anup; Yochelis, Shira; Capua, Eyal; Carmieli, Raanan; Paltiel, Yossi; Naaman, Ron; Michaeli, Karen
      Journal of Physical Chemistry Letters (2019), 10 (5), 1139-1145CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      We study GaAs/AlGaAs devices hosting a two-dimensional electron gas and coated with a monolayer of chiral org. mols. We observe clear signatures of room-temp. magnetism, which is induced in these systems by applying a gate voltage. We explain this phenomenon as a consequence of the spin-polarized charges that are injected into the semiconductor through the chiral mols. The orientation of the magnetic moment can be manipulated by low gate voltages, with a switching rate in the megahertz range. Thus, our devices implement an efficient, elec. field-controlled magnetization, which has long been desired for their tech. prospects.
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      (e) Wang, C.; Danovich, D.; Chen, H.; Shaik, S. Oriented External Electric Fields: Tweezers and Catalysts for Reactivity in Halogen-Bond Complexes. J. Am. Chem. Soc. 2019, 141, 7122– 7136,  DOI: 10.1021/jacs.9b02174
      9e
      Oriented External Electric Fields: Tweezers and Catalysts for Reactivity in Halogen-Bond Complexes
      Wang, Chao; Danovich, David; Chen, Hui; Shaik, Sason
      Journal of the American Chemical Society (2019), 141 (17), 7122-7136CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      This theor. study establishes ways of controlling and enabling an uncommon chem. reaction, the displacement reaction, B:---(X-Y) → (B-X)+ + :Y-, which is nascent from a B:---(X-Y) halogen bond (XB) by nucleophilic attack of the base, B:, on the halogen, X. In most of the 14 cases examd., these reactions possess high barriers either in the gas phase (where the X-Y bond dissocs. to radicals) or in solvents such as CH2Cl2 and CH3CN (which lead to endothermic processes). Thus, generally, the XB species are trapped in deep min., and their reactions are not allowed without catalysis. However, when an oriented-external elec. field (OEEF) is directed along the B---X---Y reaction axis, the field acts as elec. tweezers that orient the XB along the field's axis, and intensely catalyze the process, by tens of kcal/mol, thus rendering the reaction allowed. Flipping the OEEF along the reaction axis inhibits the reaction and weakens the interaction of the XB. Furthermore, at a crit. OEEF, each XB undergoes spontaneous and barrier-free reaction. As such, OEEF achieves quite tight control of the structure and reactivity of XB species. Valence bond modeling is used to elucidate the means whereby OEEFs exert their control.
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      (f) Yeh, C.-H.; Pham, T. M. L.; Nachimuthu, S.; Jiang, J.-C. Effect of External Electric Field on Methane Conversion on IrO2(110) Surface: A Density Functional Theory Study. ACS Catal. 2019, 9, 8230– 8242,  DOI: 10.1021/acscatal.9b01910
      9f
      Effect of External Electric Field on Methane Conversion on IrO2(110) Surface: A Density Functional Theory Study
      Yeh, Chen-Hao; Pham, Thong Minh Le; Nachimuthu, Santhanamoorthi; Jiang, Jyh-Chiang
      ACS Catalysis (2019), 9 (9), 8230-8242CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      Catalytic conversion of methane to value-added chems. is a promising application for gas versatility. In this work, we have investigated the methane oxidn. over oxygen-rich IrO2 (110) surface by DFT calcns., as IrO2 is reported to be an effective catalyst for activating the C-H bond of methane. Compared to the methane reaction on the surface of stoichiometric IrO2 (110), the reaction barrier for each step of forming formaldehyde on the oxygen-rich IrO2 (110) is small. The calcns. show that formaldehyde formation is the most favorable route in methane oxidn., but this process is limited by the high desorption energy of formaldehyde. To modify the reactivity of IrO2 (110), we conducted a study of the influence of an external elec. field on the methane conversion reaction. The calcns. show that the effects of external elec. field on methane dehydrogenation and C-O coupling reactions are not so apparent. However, it is found that the desorption energy of the adsorbates can be regulated by applying an external elec. field. Our study indicates that the use of an external elec. field is crucial in regulating the catalytic reaction, and esp. the application of a pos. elec. field promotes the oxidn. of methane to formaldehyde over oxygen-rich IrO2 (110) surface.
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      (g) Zhang, M.-X.; Xu, H.-L. A Greener Catalyst for Hydroboration of Imines─External Electric Field Modify the Reaction Mechanism. J. Comput. Chem. 2019, 40, 1772– 1779,  DOI: 10.1002/jcc.25830
      9g
      A greener catalyst for hydroboration of imines-external electric field modify the reaction mechanism
      Zhang, Ming-Xia; Xu, Hong-Liang
      Journal of Computational Chemistry (2019), 40 (19), 1772-1779CODEN: JCCHDD; ISSN:0192-8651. (John Wiley & Sons, Inc.)
      Usually, an extra catalyst (for example, the transition metal complexes) need to be used in catalyzing hydroboration, which involved the cost, environment, and so forth. Here, a greener and controllable catalyst-external elec. field (EEF) was used to study its effect on hydroboration of N-(4-methylbenzyl)aniline (PhN=CHPhMe) with pinacolboane (HBPin). The results demonstrated that EEF could affect the barrier heights of both two pathways of this reaction. More significantly, flipping the direction of EEF could modify the reaction mechanism to induce a dominant inverse hydroboration at some field strength. That is to say, oriented EEF is a controlling switch for the anti- or Markovnikov hydroboration reaction of imines. This investigation is meaningful for the exploration of greener catalyst for chem. reaction and guide a new method for the Markovnikov hydroboration addn.
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      (h) He, C. Q.; Lam, C. C.; Yu, P.; Song, Z.; Chen, M.; Lam, Y.-h.; Chen, S.; Houk, K. N. Catalytic Effects of Ammonium and Sulfonium Salts and External Electric Fields on Aza-Diels–Alder Reactions. J. Org. Chem. 2020, 85, 2618– 2625,  DOI: 10.1021/acs.joc.9b03446
      9h
      Catalytic Effects of Ammonium and Sulfonium Salts and External Electric Fields on Aza-Diels-Alder Reactions
      He, Cyndi Qixin; Lam, Ching Ching; Yu, Peiyuan; Song, Zhihui; Chen, Maggie; Lam, Yu-hong; Chen, Shuming; Houk, K. N.
      Journal of Organic Chemistry (2020), 85 (4), 2618-2625CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)
      The mechanism of the aza-Diels-Alder reaction catalyzed by tetraalkylammonium or trialkylsulfonium salts is explored with d. functional theory. Favorable electrostatic interactions between the dienophile and the charged catalyst stabilize the highly polar transition state, leading to lower free energy barriers and higher dipole moments. Endo selectivity is predicted for both uncatalyzed and catalyzed systems. We also computationally evaluate the effects of oriented external elec. fields (EEFs) on the same aza-Diels-Alder reaction, demonstrating that very strong EEFs would be needed to achieve the catalytic strength of these cationic catalysts.
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      (i) Wang, W.-W.; Shang, F.-L.; Zhao, X. Curved Carbon Skeleton in Oriented External Electric Fields: Modulated Curvature, Directional Bowl Inversion, and Face-Selective Cycloadditions of Corannulene. Org. Lett. 2020, 22, 4786– 4791,  DOI: 10.1021/acs.orglett.0c01595
      9i
      Curved Carbon Skeleton in Oriented External Electric Fields: Modulated Curvature, Directional Bowl Inversion, and Face-Selective Cycloadditions of Corannulene
      Wang, Wei-Wei; Shang, Fu-Lin; Zhao, Xiang
      Organic Letters (2020), 22 (12), 4786-4791CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
      We introduced the oriented-external-elec.-field-induced modification of bowl-shaped corannulene using d. functional theory calcns. The results show that the elec. field is capable of significantly modulating the polarization and electrostatic characteristics of the concave and convex surfaces of buckybowls. The structure-energy-reactivity relation can be precisely controlled, leading to a variety of unconventional properties for practical applications.
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      (j) Zhang, R.; Warren, J. J. Controlling the Oxygen Reduction Selectivity of Asymmetric Cobalt Porphyrins by Using Local Electrostatic Interactions. J. Am. Chem. Soc. 2020, 142, 13426– 13434,  DOI: 10.1021/jacs.0c03861
      9j
      Controlling the Oxygen Reduction Selectivity of Asymmetric Cobalt Porphyrins by Using Local Electrostatic Interactions
      Zhang, Rui; Warren, Jeffrey J.
      Journal of the American Chemical Society (2020), 142 (31), 13426-13434CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      The development and improvement of electrocatalysts for the 4H+/4e- redn. of O2 to H2O is an ongoing challenge. The addn. of ancillary groups (e.g., hydrogen bonding, Bronsted acid/base) near the active site of metal-contg. catalysts is an effective way to improve selectivity and kinetics of the oxygen redn. reaction (ORR). In this regard, iron porphyrins are among the most researched ORR catalysts. Closely related cobalt porphyrin ORR catalysts can function closer to the O2/H2O thermodn. potential, but they tend to be less selective and follow a different mechanism than for the iron porphyrins. Herein, strategies are explored to extend the ideas about ancillary groups that have been developed for iron porphyrin ORR electrocatalysts to improve the performance of the corresponding cobalt complexes. A series of porphyrin electrocatalysts are described that are modified versions of Co(5,10,15,20-tetraphenylporphyrin), where the 2-position of one of the Ph groups contains -NH2, -N(CH3)2, and -N(CH3)3+. Investigations using cyclic voltammetry and hydrodynamic electrochem. show that the presence of a cationic ancillary group gives rise to a catalyst that is selective for the conversion of O2 to H2O across a wide pH range. In contrast, the other catalysts are selective for redn. of O2 to H2O at pH 0, but produce H2O2 at higher pH. The ORR rate (~ 106 M-1 s-1) and selectivity of the -N(CH3)3+-modified catalyst are invariant between pH 0 and 7. Quantum chem. calcns. support the hypothesis that the enhancement of selectivity can be attributed to the distinct mechanism of O2 redn. by Co-porphyrins. Specifically, the mechanism relies on anionic, peroxide-bound intermediates. While protic ancillary groups are important in the performance of iron porphyrin ORR catalysts, it is suggested that electrostatic stabilizers of O2-bound intermediates are more crucial for cobalt porphyrin ORR catalysts.
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      (k) Gheorghiu, A.; Coveney, P. V.; Arabi, A. A. The Influence of External Electric Fields on Proton Transfer Tautomerism in the Guanine–Cytosine Base Pair. Phys. Chem. Chem. Phys. 2021, 23, 6252– 6265,  DOI: 10.1039/D0CP06218A
      9k
      The influence of external electric fields on proton transfer tautomerism in the guanine-cytosine base pair
      Gheorghiu, Alexander; Coveney, Peter V.; Arabi, Alya A.
      Physical Chemistry Chemical Physics (2021), 23 (10), 6252-6265CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      The Watson-Crick base pair proton transfer tautomers would be widely considered as a source of spontaneous mutations in DNA replication if not for their short lifetimes and thermodn. instability. This work investigates the effects external elec. fields have on the stability of the guanine-cytosine proton transfer tautomers within a realistic strand of aq. DNA using a combination of ensemble-based classical mol. dynamics (MD) coupled to quantum mechanics/mol. mechanics (QM/MM). Performing an ensemble of calcns. accounts for the stochastic aspects of the simulations while allowing for easier identification of systematic errors. The methodol. applied in this work has previously been shown to est. base pair proton transfer rate coeffs. that are in good agreement with recent exptl. data. A range of elec. fields in the order of 104 to 109 V m-1 is investigated based on their real-life medicinal applications which include gene therapy and cancer treatments. The MD trajectories confirm that elec. fields up to 1.00 x 109 V m-1 have a negligible influence on the structure of the base pairs within DNA. The QM/MM results show that the application of large external elec. fields (1.00 x 109 V m-1) parallel to the hydrogen bonds increases the thermodn. population of the tautomers by up to one order of magnitude; moreover, the lifetimes of the tautomers remain insignificant when compared to the timescale of DNA replication.
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      (l) Hennefarth, M. R.; Alexandrova, A. N. Heterogeneous Intramolecular Electric Field as a Descriptor of Diels–Alder Reactivity. J. Phys. Chem. A 2021, 125, 1289– 1298,  DOI: 10.1021/acs.jpca.1c00181
      9l
      Heterogeneous Intramolecular Electric Field as a Descriptor of Diels-Alder Reactivity
      Hennefarth, Matthew R.; Alexandrova, Anastassia N.
      Journal of Physical Chemistry A (2021), 125 (5), 1289-1298CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
      External elec. fields have proven to be an effective tool in catalysis, on par with pressure and temp., affecting the thermodn. and kinetics of a reaction. However, fields in mols. are complicated heterogeneous vector objects, and there is no universal recipe for grasping the exact features of these fields that implicate reactivity. Herein, we demonstrate that topol. features of the heterogeneous elec. field within the reactant state and of the quantum mech. electron d. - a scalar reporter on the field experienced by the system - can be identified as rigorous descriptors of the reactivity to follow. We scrutinize specifically the Diels-Alder reaction. Its 3D nature and the lack of a singular directionality of charge movement upon barrier crossing make the effect of the elec. field not obvious. We show that the elec. field topol. around the dienophile double bond and the assocd. changes in the topol. of the electron d. in this bond are predictors of the reaction barrier. They are also the metrics to rationalize and predict how the external field would inhibit or enhance the reaction. The findings pave the way toward designing external fields for catalysis and reading the reactivity without an explicit mechanistic interrogation, for a variety of reactions.
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      (m) Martin, D. J.; Mayer, J. M. Oriented Electrostatic Effects on O2 and CO2 Reduction by a Polycationic Iron Porphyrin. J. Am. Chem. Soc. 2021, 143, 11423– 11434,  DOI: 10.1021/jacs.1c03132
      9m
      Oriented Electrostatic Effects on O2 and CO2 Reduction by a Polycationic Iron Porphyrin
      Martin, Daniel J.; Mayer, James M.
      Journal of the American Chemical Society (2021), 143 (30), 11423-11434CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Next-generation energy technologies require improved methods for rapid and efficient chem.-to-elec. energy transformations. One new approach has been to include atomically positioned, electrostatic motifs in mol. catalysts to stabilize high-energy, charged intermediates. For example, an iron porphyrin bearing four cationic, o-N,N,N-trimethylanilinium groups (o-[N(CH3)3]+) has recently been used to catalyze the complex, multistep O2 and CO2 redn. reactions (ORR and CO2RR) with fast rates and at low overpotentials. The success of this catalyst is attributed, at least in part, to specific charge-charge interactions between the atomically positioned o-[N(CH3)3]+ groups and the bound substrate. However, by nature of the mono-ortho substitution pattern, there are four possible atropisomers of this metalloporphyrin and thus four unique electrostatic environments. This work reports that each of the four individual atropisomers catalyzes both the ORR and CO2RR with fast rates and low overpotentials. The max. turnover frequencies vary among the atropisomers, by a factor of 60 for the ORR and a factor of 5 for CO2RR. For the ORR, the αβαβ isomer is the fastest and has the highest overpotential, while for the CO2RR the αααα isomer is the fastest and has the highest overpotential. The role of charge positioning is complex and can affect more than a single step such as CO2 binding. These data offer a first-of-a-kind perspective on atomically positioned charge and highlight the significance of high charge d., rather than orientation, on the thermodn. and kinetics of multistep mol. electrochem. transformations.
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      (n) Mejía, L.; Garay-Ruiz, D.; Franco, I. Diels–Alder Reaction in a Molecular Junction. J. Phys. Chem. C 2021, 125, 14599– 14606,  DOI: 10.1021/acs.jpcc.1c01901
      9n
      Diels-Alder Reaction in a Molecular Junction
      Mejia, Leopoldo; Garay-Ruiz, Diego; Franco, Ignacio
      Journal of Physical Chemistry C (2021), 125 (27), 14599-14606CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      We computationally investigate the utility of mol. junctions to probe chem. reactivity at the single-mol. limit. To do so, we employ mol. dynamics (MD) coupled to quantum transport simulations to investigate the classic Diels-Alder reaction but in the context of nanoscale junctions where the reactants are nanoconfined and the reactive pair is mech. brought to proximity. To capture reactive events, the MD employs the d. functional tight binding method to account for interat. interactions. To understand the thermodn. driving forces behind the reaction in this novel chem. environment, we reconstruct the potential of mean force along the reaction coordinate and decomp. it into energetic and entropic contributions. The anal. demonstrates that the process is entropically penalized, which makes the reaction barrier sensitive to changes in the temp. and reactant rigidity. The simulations further show that in nanojunctions the degree of reactivity can be mech. manipulated simply by controlling the proximity of the electrodes. Surprisingly, for optimal electrode sepns., the entropic and energetic cost in the nanoconfined reaction coincides with that obsd. in bulk, establishing a clear connection between measurements performed in these two vastly different reactive environments. Finally, we show how conductance measurements can be used to exptl. monitor the process at the single-entity limit.
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      (o) Wang, W.-W.; Shang, F.-L.; Zhao, X. Switchable (2 + 2) and (4 + 2) Cycloadditions on Boron Nitride Nanotubes under Oriented External Electric Fields: A Mechanistic Study. J. Org. Chem. 2021, 86, 3785– 3791,  DOI: 10.1021/acs.joc.0c02590
      9o
      Switchable (2 + 2) and (4 + 2) Cycloadditions on Boron Nitride Nanotubes under Oriented External Electric Fields: A Mechanistic Study
      Wang, Wei-Wei; Shang, Fu-Lin; Zhao, Xiang
      Journal of Organic Chemistry (2021), 86 (5), 3785-3791CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)
      The (2 + 2) and (4 + 2) cycloaddns. are important approaches for the functional derivatizations of nanocarbon and hexagonal boron nitride (hBN) materials. However, as two competing reactions with similar reactivity, it is difficult to control the type of reactions and the corresponding adducts in practice. Here, we introduced a mechanistic study of the oriented external elec. field (OEEF)-modulated cycloaddns. of pristine and substituted benzynes on the zigzag boron nitride nanotubes. Owing to the distinct charge transfer directions between the competing (2 + 2) and (4 + 2) reactions and the resultant distinct responses of the barriers to the fields along the tube axis, we found that OEEF plays opposing catalytic roles in these two types of reactions and the effect of elec. field as a catalyst or inhibitor can be easily reversed by flipping the field vector to achieve selective reactions and products at will.
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    10. 10
      (a) Ciampi, S.; Darwish, N.; Aitken, H. M.; Díez-Pérez, I.; Coote, M. L. Harnessing Electrostatic Catalysis in Single Molecule, Electrochemical and Chemical Systems: a Rapidly Growing Experimental Tool Box. Chem. Soc. Rev. 2018, 47, 5146– 5164,  DOI: 10.1039/C8CS00352A
      10a
      Harnessing electrostatic catalysis in single molecule, electrochemical and chemical systems: a rapidly growing experimental tool box
      Ciampi, Simone; Darwish, Nadim; Aitken, Heather M.; Diez-Perez, Ismael; Coote, Michelle L.
      Chemical Society Reviews (2018), 47 (14), 5146-5164CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      Static electricity is central to many day-to-day practical technologies, from sepn. methods in the recycling of plastics to transfer inks in photocopying, but the exploration of how electrostatics affects chem. bonding is still in its infancy. As shown in the Companion Tutorial, the presence of an appropriately-oriented elec. field can enhance the resonance stabilization of transition states by lowering the energy of ionic contributors, and the effect that follows on reaction barriers can be dramatic. However, the electrostatic effects are strongly directional and harnessing them in practical expts. has proven elusive until recently. This tutorial outlines some of the exptl. platforms through which we have sought to translate abstr. theor. concepts of electrostatic catalysis into practical chem. technologies. We move step-wise from the nano to the macro, using recent examples drawn from single-mol. STM expts., surface chem. and pH-switches in soln. chem. The expts. discussed in the tutorial will educate the reader in some of the viable solns. to gain control of the orientation of reagents in that field; from pH-switchable bond-dissocns. using charged functional groups to the use of surface chem. and surface-probe techniques. All of these recent works provide proof-of-concept of electrostatic catalysis for specific sets of chem. reactions. They overturn the long-held assumption that static electricity can only affect rates and equil. position of redox reactions, but most importantly, they provide glimpses of the wide-ranging potential of external elec. fields for controlling chem. reactivity and selectivity.
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      (b) Simpson, G. J.; García-López, V.; Daniel Boese, A.; Tour, J. M.; Grill, L. How to control single-molecule rotation. Nat. Commun. 2019, 10, 4631  DOI: 10.1038/s41467-019-12605-8
      10b
      How to control single-molecule rotation
      Simpson Grant J; Grill Leonhard; Garcia-Lopez Victor; Tour James M; Daniel Boese A
      Nature communications (2019), 10 (1), 4631 ISSN:.
      The orientation of molecules is crucial in many chemical processes. Here, we report how single dipolar molecules can be oriented with maximum precision using the electric field of a scanning tunneling microscope. Rotation is found to occur around a fixed pivot point that is caused by the specific interaction of an oxygen atom in the molecule with the Ag(111) surface. Both directions of rotation are realized at will with 100% directionality. Consequently, the internal dipole moment of an individual molecule can be spatially mapped via its behavior in an applied electric field. The importance of the oxygen-surface interaction is demonstrated by the addition of a silver atom between a single molecule and the surface and the consequent loss of the pivot point.
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    11. 11
      Bandrauk, A. D.; Sedik, E.-W. S.; Matta, C. F. Effect of Absolute Laser Phase on Reaction Paths in Laser-Induced Chemical Reactions. J. Chem. Phys. 2004, 121, 7764– 7775,  DOI: 10.1063/1.1793931
      11
      Effect of absolute laser phase on reaction paths in laser-induced chemical reactions
      Bandrauk, Andre D.; Sedik, El-Wallid S.; Matta, Cherif F.
      Journal of Chemical Physics (2004), 121 (16), 7764-7775CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      Potential surfaces, dipole moments, and polarizabilities are calcd. by ab initio methods [unrestricted MP2(full)/6-311++G(2d,2p)] along the reaction paths of the F + CH4 and Cl + CH4 reaction systems. It is found that in general dipole moments and polarizabilities exhibit peaks near the transition state. In the case of X = F these peaks are on the products side and in the case of X = Cl they are on the reactants side indicating an early transition state in the case of fluorine and a late transition state in the case of chlorine. An anal. of the geometric changes along the reaction paths reveals a one-to-one correspondence between the peaks in the elec. properties and peaks in the rate of change of certain internal geometric coordinates along the reaction path. Interaction with short IR intense laser fields pulses leads to the possibility of interferences between the dipole and polarizability laser-mol. interactions as a function of laser phase. The larger dipole moment in the Cl + CH4 reaction can lead to the creation of deep wells (instead of energy barriers) and new strongly bound states in the transition state region. This suggests possible coherent control of the reaction path as a function of the abs. phase of the incident field, by significant modification of the potential surfaces along the reaction path and, in particular, in the transition state region.
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    12. 12
      Climent, C.; Galego, J.; Garcia-Vidal, F. J.; Feist, J. Plasmonic Nanocavities Enable Self-Induced Electrostatic Catalysis. Angew. Chem., Int. Ed. 2019, 58, 8698– 8702,  DOI: 10.1002/anie.201901926
      12
      Plasmonic Nanocavities Enable Self-Induced Electrostatic Catalysis
      Climent, Claudia; Galego, Javier; Garcia-Vidal, Francisco J.; Feist, Johannes
      Angewandte Chemie, International Edition (2019), 58 (26), 8698-8702CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The potential of strong interactions between light and matter remains to be further explored within a chem. context. Towards this end herein the authors study the electromagnetic interaction between mols. and plasmonic nanocavities. By electronic structure calcns., self-induced catalysis emerges without any external stimuli through the interaction of the mol. permanent and fluctuating dipole moments with the plasmonic cavity modes. This scheme was exploited to modify the transition temp. T1/2 of spin-crossover complexes as an example of how strong light-matter interactions can ultimately be used to control a materials responses.
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    13. 13
      (a) Li, A.; Zi, Y.; Guo, H.; Wang, Z. L.; Fernández, F. M. Triboelectric Nanogenerators for Sensitive Nano-Coulomb Molecular Mass Spectrometry. Nat. Nanotechnol. 2017, 12, 481– 487,  DOI: 10.1038/nnano.2017.17
      13a
      Triboelectric nanogenerators for sensitive nano-coulomb molecular mass spectrometry
      Li, Anyin; Zi, Yunlong; Guo, Hengyu; Wang, Zhong Lin; Fernandez, Facundo M.
      Nature Nanotechnology (2017), 12 (5), 481-487CODEN: NNAABX; ISSN:1748-3387. (Nature Publishing Group)
      Ion sources for mol. mass spectrometry are usually driven by d.c. power supplies with no user control over the total charges generated. Here, we show that the output of triboelec. nanogenerators (TENGs) can quant. control the total ionization charges in mass spectrometry. The high output voltage of TENGs can generate single- or alternating-polarity ion pulses, and is ideal for inducing nanoelectrospray ionization (nanoESI) and plasma discharge ionization. For a given nanoESI emitter, accurately controlled ion pulses ranging from 1.0 to 5.5 nC were delivered with an onset charge of 1.0 nC. Spray pulses can be generated at a high frequency of 17 Hz (60 ms in period) and the pulse duration is adjustable on-demand between 60 ms and 5.5 s. Highly sensitive (∼0.6 zeptomole) mass spectrometry anal. using minimal sample (18 pl per pulse) was achieved with a 10 pg ml-1 cocaine sample. We also show that native protein conformation is conserved in TENG-ESI, and that patterned ion deposition on conductive and insulating surfaces is possible.
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      (b) Xia, H.; Wang, Z. Piezoelectricity Drives Organic Synthesis. Science 2019, 366, 1451– 1452,  DOI: 10.1126/science.aaz9758
      13b
      Piezoelectricity drives organic synthesis
      Xia, Hesheng; Wang, Zhenhua
      Science (Washington, DC, United States) (2019), 366 (6472), 1451-1452CODEN: SCIEAS; ISSN:1095-9203. (American Association for the Advancement of Science)
      The coupling of mech. and chem. phenomena on a mol. scale, mechanochem., is undergoing an exciting period of rediscovery and renaissance (). Mechanochem. research can provide deep insight into the rupture mechanism of chem. bonds (). Mechanochem. routes for chem. synthesis can minimize the use of hazardous or undesirable solvents. They also can generate materials along reaction pathways that are inaccessible through thermal or light-activated processes. On page 1500 of this issue, Kubota et al. demonstrate that piezoelec. materials can be used as mechanoredox catalysts for org. synthesis ().
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      (c) Zhang, J.; Ciampi, S. Shape and Charge: Faraday’s Ice Pail Experiment Revisited. ACS Cent. Sci. 2020, 6, 611– 612,  DOI: 10.1021/acscentsci.0c00298
      13c
      Shape and Charge: Faraday's Ice Pail Experiment Revisited
      Zhang, Jinyang; Ciampi, Simone
      ACS Central Science (2020), 6 (5), 611-612CODEN: ACSCII; ISSN:2374-7951. (American Chemical Society)
      A review. Faraday pail measurements of charged dielecs. are not as straightforward as previously thought.
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    14. 14
      Grahame, D. C. The Electrical Double Layer and the Theory of Electrocapillarity. Chem. Rev. 1947, 41, 441– 501,  DOI: 10.1021/cr60130a002
      14
      The electrical double layer and the theory of electro-capillarity
      Grahame, David C.
      Chemical Reviews (Washington, DC, United States) (1947), 41 (), 441-501CODEN: CHREAY; ISSN:0009-2665.
      A review with 95 references.
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    15. 15
      Heo, J.; Ahn, H.; Won, J.; Son, J. G.; Shon, H. K.; Lee, T. G.; Han, S. W.; Baik, M. H. Electro-inductive effect: Electrodes as functional groups with tunable electronic properties. Science 2020, 370, 214– 219,  DOI: 10.1126/science.abb6375
      15
      Electro-inductive effect: Electrodes as functional groups with tunable electronic properties
      Heo, Joon; Ahn, Hojin; Won, Joonghee; Son, Jin Gyeong; Shon, Hyun Kyong; Lee, Tae Geol; Han, Sang Woo; Baik, Mu-Hyun
      Science (Washington, DC, United States) (2020), 370 (6513), 214-219CODEN: SCIEAS; ISSN:1095-9203. (American Association for the Advancement of Science)
      In place of functional groups that impose different inductive effects, we immobilize mols. carrying thiol groups on a gold electrode. By applying different voltages, the properties of the immobilized mols. can be tuned. The base-catalyzed sapon. of benzoic esters is fully inhibited by applying a mildly neg. voltage of -0.25 V vs. open circuit potential. Furthermore, the rate of a Suzuki-Miyaura cross-coupling reaction can be changed by applying a voltage when the arylhalide substrate is immobilized on a gold electrode. Finally, a two-step carboxylic acid amidation is shown to benefit from a switch in applied voltage between addn. of a carbodiimide coupling reagent and introduction of the amine.
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    16. 16
      Patrow, J. G.; Sorenson, S. A.; Dawlaty, J. M. Direct Spectroscopic Measurement of Interfacial Electric Fields near an Electrode under Polarizing or Current-Carrying Conditions. J. Phys. Chem. C 2017, 121, 11585– 11592,  DOI: 10.1021/acs.jpcc.7b03134
      16
      Direct Spectroscopic Measurement of Interfacial Electric Fields near an Electrode under Polarizing or Current-Carrying Conditions
      Patrow, Joel G.; Sorenson, Shayne A.; Dawlaty, Jahan M.
      Journal of Physical Chemistry C (2017), 121 (21), 11585-11592CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      Interfacial elec. fields and the related mol. polarization are the central quantities that govern charge transfer between an electrode and a mol. The presence of the interfacial field is often inferred indirectly through transport and capacitance measurements. It is desirable to measure such fields directly via the Stark shift that they induce on mol. vibrations. We report the Stark shift of a well-known vibrational chromophore tethered near an electrochem. interface measured using vibrational sum frequency generation spectroscopy. We have two important findings. First, we observe that the measured local field scales with respect to the ionic concn. in the electrolyte according to a model that combines the Gouy-Chapman theory with the capacitive response of a mol. layer. This behavior holds over 3 orders of magnitude in ionic concn., therefore lending support to the validity of the model. Our results along with this model allow for estn. of the elec. field near the electrode as the potential and ionic concn. are varied. Second, we observe that the mentioned variation of the local field with changing potential only occurs for pos. potentials, for which the electrode is polarized but negligible current flows. For neg. potentials, a sustained electrochem. current is obsd. that likely arises due to electron transfer and subsequent redn. of protons in the electrolyte. Interestingly, we observe that, under this condition, the local field does not vary with increasingly neg. applied potential, reminiscent of the field within a leaky capacitor. The important consequence of this observation is that an increase in the thermodn. drive for an electrochem. reaction does not necessarily translate to increased mol. polarization near the surface when a sustained current is passing. This study will serve as a baseline in all areas of chem. in which understanding the role of local fields near interfaces is important and will provide a new perspective for interfacial charge transfer theories.
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    17. 17
      (a) Ge, A.; Videla, P. E.; Lee, G. L.; Rudshteyn, B.; Song, J.; Kubiak, C. P.; Batista, V. S.; Lian, T. Interfacial Structure and Electric Field Probed by in Situ Electrochemical Vibrational Stark Effect Spectroscopy and Computational Modeling. J. Phys. Chem. C 2017, 121, 18674– 18682,  DOI: 10.1021/acs.jpcc.7b05563
      17a
      Interfacial Structure and Electric Field Probed by in Situ Electrochemical Vibrational Stark Effect Spectroscopy and Computational Modeling
      Ge, Aimin; Videla, Pablo E.; Lee, Gwendolynne L.; Rudshteyn, Benjamin; Song, Jia; Kubiak, Clifford P.; Batista, Victor S.; Lian, Tianquan
      Journal of Physical Chemistry C (2017), 121 (34), 18674-18682CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      Interfacial elec. fields play crucial roles in electrochem., catalysis, and solar energy conversion. Understanding of the interfacial elec. field effects was hindered by the lack of a direct spectroscopic method to probe of the interfacial field at the mol. level. Here, the authors report the characterization of the field and interfacial structure at Au/diisocyanide/aq. electrolyte interfaces, using a combination of in situ electrochem. vibrational sum frequency generation (SFG) spectroscopy, d. functional theory (DFT) calcns., and mol. dynamics (MD) simulations. For 1,4-phenylene diisocyanide (PDI), 4,4'-biphenyl diisocyanide (BPDI), and 4,4''-p-terphenyl diisocyanide (TPDI), the authors' results reveal that the frequency of the Au-bound NC stretch mode of the diisocyanide self-assembled monolayer (SAM) increases linearly with the applied potential, suggesting that SFG can be an in situ probe of the strength of the elec. field at electrode/electrolyte interfaces. Using DFT-computed Stark tuning rates of model complexes, the elec. field strength at the metal/SAM/electrolyte interfaces is 108-109 V/m. The linear dependence of the vibrational frequency (and field) with applied potential is consistent with an electrochem. double-layer structure that consists of a Helmholtz layer in contact with a diffused layer. The Helmholtz layer thickness is approx. the same as the mol. length for PDI, suggesting a well-ordered SAM with negligible electrolyte penetration. For BPDI and TPDI, the Helmholtz layer is thinner than the monolayer of mol. adsorbates, indicating that the electrolyte percolates into the SAM, as shown by mol. dynamics simulations of the Au/PDI/electrolyte interface. The reported anal. demonstrates that a combination of in situ SFG probes and computational modeling provides a powerful approach to elucidate the structure of electrochem. interfaces at the detailed mol. level.
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      (b) Clark, M. L.; Ge, A.; Videla, P. E.; Rudshteyn, B.; Miller, C. J.; Song, J.; Batista, V. S.; Lian, T.; Kubiak, C. P. CO2 Reduction Catalysts on Gold Electrode Surfaces Influenced by Large Electric Fields. J. Am. Chem. Soc. 2018, 140, 17643– 17655,  DOI: 10.1021/jacs.8b09852
      17b
      CO2 Reduction Catalysts on Gold Electrode Surfaces Influenced by Large Electric Fields
      Clark, Melissa L.; Ge, Aimin; Videla, Pablo E.; Rudshteyn, Benjamin; Miller, Christopher J.; Song, Jia; Batista, Victor S.; Lian, Tianquan; Kubiak, Clifford P.
      Journal of the American Chemical Society (2018), 140 (50), 17643-17655CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Attaching mol. catalysts to metal and semiconductor electrodes is a promising approach to developing new catalytic electrodes with combined advantages of mol. and heterogeneous catalysts. However, the effect of the interfacial elec. field on the stability, activity, and selectivity of the catalysts is often poorly understood due to the complexity of interfaces. The authors examine the strength of the interfacial field at the binding site of CO2 redn. catalysts including Re(S-2,2'-bipyridine)(CO)3Cl and Mn(S-2,2'-bipyridine)(CO)3Br immobilized on Au electrodes. The vibrational spectra are probed by sum frequency generation spectroscopy (SFG), showing pronounced potential-dependent frequency shifts of the carbonyl stretching modes. Calcns. of SFG spectra and Stark tuning rates based on d. functional theory allow for direct interpretation of the configurations of the catalysts bound to the surfaces and the influence of the interfacial elec. field. Electrocatalysts supported on Au electrodes have tilt angles of ∼65-75° relative to the surface normal with one of the carbonyl ligands in direct contact with the surface. Large interfacial elec. fields of 108-109 V/m are detd. through the anal. of exptl. frequency shifts and theor. Stark tuning rates of the sym. CO stretching mode. These large elec. fields thus significantly influence the CO2 binding site.
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      (c) Ge, A.; Rudshteyn, B.; Videla, P. E.; Miller, C. J.; Kubiak, C. P.; Batista, V. S.; Lian, T. Heterogenized Molecular Catalysts: Vibrational Sum-Frequency Spectroscopic, Electrochemical, and Theoretical Investigations. Acc. Chem. Res. 2019, 52, 1289– 1300,  DOI: 10.1021/acs.accounts.9b00001
      17c
      Heterogenized Molecular Catalysts: Vibrational Sum-Frequency Spectroscopic, Electrochemical, and Theoretical Investigations
      Ge, Aimin; Rudshteyn, Benjamin; Videla, Pablo E.; Miller, Christopher J.; Kubiak, Clifford P.; Batista, Victor S.; Lian, Tianquan
      Accounts of Chemical Research (2019), 52 (5), 1289-1300CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
      A review. Rhenium and manganese bipyridyl tricarbonyl complexes have attracted intense interest for their promising applications in photocatalytic and electrocatalytic CO2 redn. in both homogeneous and heterogenized systems. To date, there have been extensive studies on immobilizing Re catalysts on solid surfaces for higher catalytic efficiency, reduced catalyst loading, and convenient product sepn. However, in order for the heterogenized mol. catalysts to achieve the combination of the best aspects of homogeneous and heterogeneous catalysts, it is essential to understand the fundamental physicochem. properties of such heterogeneous systems, such as surface-bound structures of Re/Mn catalysts, substrate-adsorbate interactions, and photoinduced or elec.-field-induced effects on Re/Mn catalysts. For example, the surface may act to (un)block substrates, (un)trap charges, (de)stabilize particular intermediates (and thus affect scaling relations), and shift potentials in different directions, just as protein environments do. The close collaboration between the Lian, Batista, and Kubiak groups has resulted in an integrated approach to investigate how the semiconductor or metal surface affects the properties of the attached catalyst. Synthetic strategies to achieve stable and controlled attachment of Re/Mn mol. catalysts have been developed. Steady-state, time-resolved, and electrochem. vibrational sum-frequency generation (SFG) spectroscopic studies have provided insight into the effects of interfacial structures, ultrafast vibrational energy relaxation, and elec. field on the Re/Mn catalysts, resp. Various computational methods utilizing d. functional theory (DFT) have been developed and applied to det. the mol. orientation by direct comparison to spectroscopy, unravel vibrational energy relaxation mechanisms, and quantify the interfacial elec. field strength of the Re/Mn catalyst systems.This Account starts with a discussion of the recent progress in detg. the surface-bound structures of Re catalysts on semiconductor and Au surfaces by a combined vibrational SFG and DFT study. The effects of crystal facet, length of anchoring ligands, and doping of the semiconductor on the bound structures of Re catalysts and of the substrate itself are discussed. This is followed by a summary of the progress in understanding the vibrational relaxation (VR) dynamics of Re catalysts covalently adsorbed on semiconductor and metal surfaces. The VR processes of Re catalysts on TiO2 films and TiO2 single crystals and a Re catalyst tethered on Au, particularly the role of electron-hole pair (EHP)-induced coupling on the VR of the Re catalyst bound on Au, are discussed. The Account also summarizes recent studies in quantifying the elec. field strength experienced by the catalytically active site of the Re/Mn catalyst bound on a Au electrode based on a combined electrochem. SFG and DFT study of the Stark tuning of the CO stretching modes of these catalysts. Finally, future research directions on surface-immobilized mol. catalyst systems are discussed.
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    18. 18
      (a) Fried, S. D.; Boxer, S. G. Electric Fields and Enzyme Catalysis. Annu. Rev. Biochem. 2017, 86, 387– 415,  DOI: 10.1146/annurev-biochem-061516-044432
      18a
      Electric Fields and Enzyme Catalysis
      Fried, Stephen D.; Boxer, Steven G.
      Annual Review of Biochemistry (2017), 86 (), 387-415CODEN: ARBOAW; ISSN:0066-4154. (Annual Reviews)
      A review. What happens inside an enzyme's active site to allow slow and difficult chem. reactions to occur so rapidly. This question has occupied biochemists' attention for a long time. Computer models of increasing sophistication have predicted an important role for electrostatic interactions in enzymic reactions, yet this hypothesis has proved vexingly difficult to test exptl. Recent expts. utilizing the vibrational Stark effect make it possible to measure the elec. field a substrate mol. experiences when bound inside its enzyme's active site. These expts. have provided compelling evidence supporting a major electrostatic contribution to enzymic catalysis. Here, we review these results and develop a simple model for electrostatic catalysis that enables us to incorporate disparate concepts introduced by many investigators to describe how enzymes work into a more unified framework stressing the importance of elec. fields at the active site.
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      (b) Vaissier Welborn, V.; Head-Gordon, T. Computational Design of Synthetic Enzymes. Chem. Rev. 2019, 119, 6613– 6630,  DOI: 10.1021/acs.chemrev.8b00399
      18b
      Computational Design of Synthetic Enzymes
      Vaissier Welborn, Valerie; Head-Gordon, Teresa
      Chemical Reviews (Washington, DC, United States) (2019), 119 (11), 6613-6630CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. We review the std. model for de novo computational design of enzymes, which primarily focuses on the development of an active site geometry, composed of protein functional groups in orientations optimized to stabilize the transition state, for a novel chem. reaction not found in nature. Its emphasis is placed on the structure and energetics of the active site embedded in an accommodating protein that serves as a phys. support that shields the reaction chem. from solvent, which is typically improved upon using lab. directed evolution. We also provide a review of design strategies that move beyond the std. model, by placing more emphasis on the designed enzyme as a whole catalytic construct. Starting with complete de novo enzyme design examples, we consider addnl. design factors such as entropy of individual residues, correlated motion between side chains (mutual information), dynamical correlations of the enzyme motions that could aid the reaction, reorganization energy, and elec. fields as a way to exploit the entire protein scaffold to improve upon the catalytic rate, thereby providing directed evolution with better starting sequences for increasing the biocatalytic performance.
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      (c) Bím, D.; Alexandrova, A. N. Electrostatic Regulation of Blue Copper Sites. Chem. Sci. 2021, 12, 11406– 11413,  DOI: 10.1039/D1SC02233D
      18c
      Electrostatic regulation of blue copper sites
      Bim, Daniel; Alexandrova, Anastassia N.
      Chemical Science (2021), 12 (34), 11406-11413CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
      In the last 50 years, the blue copper proteins became central targets of investigation. Extensive expts. focused on the Cu coordination to probe the effect of local perturbations on its properties. We found that local elec. fields, generated by charged residues evolutionarily placed throughout the protein edifice, mainly second sphere, but also more remotely, constitute an addnl. significant factor regulating blue copper proteins. These fields are not random, but exhibit a highly specific directionality, neg. with respect to the .vector.(Cu - SCys) and .vector.(Cu - SMet) vectors in the Cu first shell. The field magnitude contributes to fine-tuning of the geometric and electronic properties of Cu sites in individual blue copper proteins. Specifically, the local elec. fields evidently control the Cu-SMet bond distance, Cu(II)-SCys bond covalency, and the energies of the frontier MOs, which, in turn, govern the Cu(II/I) redn. potential and the relative absorption intensities at 450 nm and 600 nm.
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    19. 19
      (a) Shaik, S.; de Visser, S. P.; Kumar, D. External Electric Field Will Control the Selectivity of Enzymatic-Like Bond Activations. J. Am. Chem. Soc. 2004, 126, 11746– 11749,  DOI: 10.1021/ja047432k
      19a
      External Electric Field Will Control the Selectivity of Enzymatic-Like Bond Activations
      Shaik, Sason; de Visser, Sam P.; Kumar, Devesh
      Journal of the American Chemical Society (2004), 126 (37), 11746-11749CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Controlling the selectivity of a chem. reaction is a Holy Grail in chem. This paper reports theor. results of unprecedented effects induced by moderately strong elec. fields on the selectivity of two competing nonpolar bond activation processes, C-H hydroxylation vs. C:C epoxidn., promoted by an active species that is common to heme-enzymes and to metallo-org. catalysts. The mol. system by itself shows no selectivity whatsoever. However, the presence of an elec. field induces abs. selectivity that can be controlled at will. Thus, the choice of the orientation and direction of the field vis-a-vis the mol. axes drives the reaction in the direction of complete C-H hydroxylation or complete C:C epoxidn.
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      (b) Schyman, P.; Lai, W.; Chen, H.; Wang, Y.; Shaik, S. The Directive of the Protein: How Does Cytochrome P450 Select the Mechanism of Dopamine Formation?. J. Am. Chem. Soc. 2011, 133, 7977– 7984,  DOI: 10.1021/ja201665x
      19b
      The Directive of the Protein: How Does Cytochrome P450 Select the Mechanism of Dopamine Formation?
      Schyman, Patric; Lai, Wenzhen; Chen, Hui; Wang, Yong; Shaik, Sason
      Journal of the American Chemical Society (2011), 133 (20), 7977-7984CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Dopamine can be generated from tyramine via arene hydroxylation catalyzed by a cytochrome P 450 enzyme (CYP2D6). Our quantum mech./mol. mech. (QM/MM) results reveal the decisive impact of the protein in selecting the best' reaction mechanism. Instead of the traditional Meisenheimer-complex mechanism, the study reveals a mechanism involving an initial hydrogen atom transfer from the phenolic hydroxyl group of the tyramine to the iron-oxo of the compd. I (Cpd I), followed by a ring-π radical rebound that eventually leads to dopamine by keto-enol rearrangement. This mechanism is not viable in the gas phase since the O-H bond activation by Cpd I is endothermic and the process does not form a stable intermediate. By contrast, the in-protein reaction has a low barrier and is exothermic. It is shown that the local elec. field of the protein environment serves as a template that stabilizes the intermediate of the H-abstraction step and thereby mediates the catalysis of dopamine formation at a lower energy cost. Furthermore, it is shown that external elec. fields can either catalyze or inhibit the process depending on their directionality.
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      (c) Stuyver, T.; Ramanan, R.; Mallick, D.; Shaik, S. Oriented (Local) Electric Fields Drive the Millionfold Enhancement of the H-Abstraction Catalysis Observed for Synthetic Metalloenzyme Analogues. Angew. Chem., Int. Ed. 2020, 59, 7915– 7920,  DOI: 10.1002/anie.201916592
      19c
      Oriented (Local) Electric Fields Drive the Millionfold Enhancement of the H-Abstraction Catalysis Observed for Synthetic Metalloenzyme Analogues
      Stuyver, Thijs; Ramanan, Rajeev; Mallick, Dibyendu; Shaik, Sason
      Angewandte Chemie, International Edition (2020), 59 (20), 7915-7920CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      This contribution follows the recent remarkable catalysis obsd. by Groves et al. in hydrogen-abstraction reactions by (a) an oxoferryl porphyrin radical-cation complex [Por.++FeIV(O)Lax] and (b) a hydroxoiron porphyrazine ferric complex [PyPzFeIII(OH)Lax], both of which involve pos. charged substituents on the outer circumference of the resp. macrocyclic ligands. These charge-coronated complexes are analogs of the biol. important Compd. I (Cpd I) and synthetic hydroxoferric species, resp. We demonstrate that the obsd. enhancement of the H-abstraction catalysis for these systems is a purely electrostatic effect, elicited by the local charges embedded on the peripheries of the resp. macrocyclic ligands. Our findings provide new insights into how electrostatics can be employed to tune the catalytic activity of metalloenzymes and can thus contribute to the future design of new and highly efficient hydrogen-abstraction catalysts.
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      (d) Bím, D.; Alexandrova, A. N. Local Electric Fields As a Natural Switch of Heme-Iron Protein Reactivity. ACS Catal. 2021, 11, 6534– 6546,  DOI: 10.1021/acscatal.1c00687
      19d
      Local Electric Fields As a Natural Switch of Heme-Iron Protein Reactivity
      Bim, Daniel; Alexandrova, Anastassia N.
      ACS Catalysis (2021), 11 (11), 6534-6546CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      Heme-iron oxidoreductases operating through the high-valent FeIVO intermediates perform crucial and complicated transformations, such as oxidns. of unreactive satd. hydrocarbons. These enzymes share the same Fe coordination, only differing by the axial ligation, e.g., Cys in P 450 oxygenases, Tyr in catalases, and His in peroxidases. By examg. ~ 200 heme-iron proteins, the protein hosts exert highly specific intramol. elec. fields on the active sites, and there is a strong correlation between the direction and magnitude of this field and the protein function. In all heme proteins, the field is preferentially aligned with the Fe-O bond (Fz). The Cys-ligated P 450 oxygenases have the highest av. Fz of 28.5 MV cm-1, i.e., most enhancing the oxyl-radical character of the oxo group, and consistent with the ability of these proteins to activate strong C-H bonds. In contrast, in Tyr-ligated proteins, the av. Fz is only 3.0 MV cm-1, apparently suppressing single-electron off-pathway oxidns., and in His-ligated proteins, Fz is -8.7 MV cm-1. The operational field range is given by the trade-off between the low reactivity of the FeIVO compd. I at the more neg. Fz and the low selectivity at the more pos. Fz. Consequently, a heme-iron site placed in the field characteristic of another heme-iron protein class loses its canonical function and gains an adverse one. Thus, elec. fields produced by the protein scaffolds, together with the nature of the axial ligand, control all heme-iron chem.
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      (e) Ramanan, R.; Waheed, S. O.; Schofield, C. J.; Christov, C. Z. What Is the Catalytic Mechanism of Enzymatic Histone N-Methyl Arginine Demethylation and Can It Be Influenced by an External Electric Field?. Chem.─Eur. J. 2021, 27, 11827– 11836,  DOI: 10.1002/chem.202101174
      19e
      What is the Catalytic Mechanism of Enzymatic Histone N-Methyl Arginine Demethylation and Can It be Influenced by an External Electric Field?
      Ramanan, Rajeev; Waheed, Sodiq O.; Schofield, Christopher J.; Christov, Christo Z.
      Chemistry - A European Journal (2021), 27 (46), 11827-11836CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Arginine methylation is an important mechanism of epigenetic regulation. Some Fe(II) and 2-oxoglutarate dependent Jumonji-C (JmjC) Nε-Me lysine histone demethylases also have N-Me arginine demethylase activity. We report combined mol. dynamic (MD) and Quantum Mech./Mol. Mech. (QM/MM) studies on the mechanism of N-Me arginine demethylation by human KDM4E and compare the results with those reported for N-Me lysine demethylation by KDM4A. At the KDM4E active site, Glu191, Asn291, and Ser197 form a conserved scaffold that restricts substrate dynamics; substrate binding is also mediated by an out of active site hydrogen-bond between the substrate Ser1 and Tyr178. The calcns. imply that in either C-H or N-H potential bond cleaving pathways for hydrogen atom transfer (HAT) during N-Me arginine demethylation, electron transfer occurs via a σ-channel; the transition state for the N-H pathway is ∼10 kcal/mol higher than for the C-H pathway due to the higher bond dissocn. energy of the N-H bond. The results of applying external elec. fields (EEFs) reveal EEFs with pos. field strengths parallel to the Fe=O bond have a significant barrier-lowering effect on the C-H pathway, by contrast, such EEFs inhibit the N-H activation rate. The overall results imply that KDM4 catalyzed N-Me arginine demethylation and N-Me lysine demethylation occur via similar C-H abstraction and rebound mechanisms leading to Me group hydroxylation, though there are differences in the interactions leading to productive binding of intermediates.
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    20. 20
      Li, W.-L.; Head-Gordon, T. Catalytic Principles from Natural Enzymes and Translational Design Strategies for Synthetic Catalysts. ACS Cent. Sci. 2021, 7, 72– 80,  DOI: 10.1021/acscentsci.0c01556
      20
      Catalytic Principles from Natural Enzymes and Translational Design Strategies for Synthetic Catalysts
      Li, Wan-Lu; Head-Gordon, Teresa
      ACS Central Science (2021), 7 (1), 72-80CODEN: ACSCII; ISSN:2374-7951. (American Chemical Society)
      A review. As biocatalysts, enzymes are characterized by their high catalytic efficiency and strong specificity but are relatively fragile by requiring narrow and specific reactive conditions for activity. Synthetic catalysts offer an opportunity for more chem. versatility operating over a wider range of conditions but currently do not reach the remarkable performance of natural enzymes. Here we consider some new design strategies based on the contributions of nonlocal elec. fields and thermodn. fluctuations to both improve the catalytic step and turnover for rate acceleration in arbitrary synthetic catalysts through bioinspired studies of natural enzymes. With a focus on the enzyme as a whole catalytic construct, we illustrate the translational impact of natural enzyme principles to synthetic enzymes, supramol. capsules, and electrocatalytic surfaces. Designed strategies based on elec. fields and thermodn. fluctuations are considered to improve the catalytic step and turnover in synthetic catalysts through bioinspired studies of natural enzymes.
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    21. 21
      Liu, C. T.; Layfield, J. P.; Stewart, R. J.; French, J. B.; Hanoian, P.; Asbury, J. B.; Hammes-Schiffer, S.; Benkovic, S. J. Probing the Electrostatics of Active Site Microenvironments along the Catalytic Cycle for Escherichia coli Dihydrofolate Reductase. J. Am. Chem. Soc. 2014, 136, 10349– 10360,  DOI: 10.1021/ja5038947
      21
      Probing the electrostatics of active site microenvironments along the catalytic cycle for Escherichia coli dihydrofolate reductase
      Liu, C. Tony; Layfield, Joshua P.; Stewart, Robert J.; French, Jarrod B.; Hanoian, Philip; Asbury, John B.; Hammes-Schiffer, Sharon; Benkovic, Stephen J.
      Journal of the American Chemical Society (2014), 136 (29), 10349-10360CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Electrostatic interactions play an important role in enzyme catalysis by guiding ligand binding and facilitating chem. reactions. These electrostatic interactions are modulated by conformational changes occurring over the catalytic cycle. Here, the changes in active site electrostatic microenvironments were examd. for all enzyme complexes along the catalytic cycle of Escherichia coli dihydrofolate reductase (ecDHFR) by incorporation of thiocyanate probes at 2 site-specific locations in the active site. The electrostatics and degree of hydration of the microenvironments surrounding the probes were investigated with spectroscopic techniques and mixed quantum mech./mol. mech. (QM/MM) calcns. Changes in the electrostatic microenvironments along the catalytic environment led to different nitrile (CN) vibrational stretching frequencies and 13C NMR chem. shifts. These environmental changes arose from protein conformational rearrangements during catalysis. The QM/MM calcns. reproduced the exptl. measured vibrational frequency shifts of the thiocyanate probes across the catalyzed hydride transfer step, which spans the closed and occluded conformations of the enzyme. Anal. of the mol. dynamics trajectories provided insight into the conformational changes occurring between these 2 states and the resulting changes in classical electrostatics and specific H-bonding interactions. The elec. fields along the CN axes of the probes were decompd. into contributions from specific residues, ligands, and solvent mols. that make up the microenvironments around the probes. Moreover, calcn. of the elec. field along the hydride donor-acceptor axis, along with decompn. of this field into specific contributions, indicateds that the cofactor and substrate, as well as the enzyme, impose a substantial elec. field that facilitates hydride transfer. Overall, exptl. and theor. data provided evidence for significant electrostatic changes in the active site microenvironments due to conformational motion occurring over the catalytic cycle of ecDHFR.
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    22. 22
      (a) Bhowmick, A.; Sharma, S. C.; Head-Gordon, T. The Importance of the Scaffold for de Novo Enzymes: A Case Study with Kemp Eliminase. J. Am. Chem. Soc. 2017, 139, 5793– 5800,  DOI: 10.1021/jacs.6b12265
      22a
      The Importance of the Scaffold for de Novo Enzymes: A Case Study with Kemp Eliminase
      Bhowmick, Asmit; Sharma, Sudhir C.; Head-Gordon, Teresa
      Journal of the American Chemical Society (2017), 139 (16), 5793-5800CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      We report elec. field values relevant to the reactant and transition states of designed Kemp eliminases KE07 and KE70, and their improved variants from lab. directed evolution (LDE), using atomistic simulations with the AMOEBA polarizable force field. We find that catalytic base residue contributes the most to the elec. field stabilization of the transition state of the LDE variants of the KE07 and KE70 enzymes, whereas the elec. fields of the remainder of the enzyme and solvent disfavor the catalytic reaction in both cases. By contrast, we show that the electrostatic environment play a large stabilizing role for the naturally occurring enzyme ketosteroid isomerase. These results suggest that LDE is ultimately a limited strategy for improving de novo enzymes since it is largely restricted to optimization of chem. positioning in the active site, thus yielding a ∼3 order magnitude improvement over the uncatalyzed reaction, an upper bound est. based on LDE applied to comparable de novo Kemp Eliminases and other enzymes. Instead de novo enzymic reactions would most productively benefit from optimization of the electrostatics of the protein scaffold in early stages of the computational design, utilizing elec. field optimization as guidance.
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      (b) Welborn, V. V.; Head-Gordon, T. Fluctuations of Electric Fields in the Active Site of the Enzyme Ketosteroid Isomerase. J. Am. Chem. Soc. 2019, 141, 12487– 12492,  DOI: 10.1021/jacs.9b05323
      22b
      Fluctuations of Electric Fields in the Active Site of the Enzyme Ketosteroid Isomerase
      Welborn, Valerie Vaissier; Head-Gordon, Teresa
      Journal of the American Chemical Society (2019), 141 (32), 12487-12492CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      We report the effect of conformational dynamics on the fluctuations of elec. fields in the active site of the enzyme ketosteroid isomerase (KSI). While KSI is considered to be a rigid enzyme with little conformational variation to support different stages of the catalytic cycle, we show that KSI utilizes cooperative side chain motions of the entire protein scaffold outside the active site to modulate elec. fields in the active site. We find that while the active site residues Asp-40 and Tyr-16 maintain their elec. field contributions at all effective time scales, the conformational dynamics of a single active residue, Asp-103, promotes large elec. field fluctuations that contribute to different stages of the catalytic cycle, including the catalytic step and product release.
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    23. 23
      Vaissier, V.; Sharma, S. C.; Schaettle, K.; Zhang, T.; Head-Gordon, T. Computational Optimization of Electric Fields for Improving Catalysis of a Designed Kemp Eliminase. ACS Catal. 2018, 8, 219– 227,  DOI: 10.1021/acscatal.7b03151
      23
      Computational Optimization of Electric Fields for Improving Catalysis of a Designed Kemp Eliminase
      Vaissier, Valerie; Sharma, Sudhir C.; Schaettle, Karl; Zhang, Taoran; Head-Gordon, Teresa
      ACS Catalysis (2018), 8 (1), 219-227CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      Here we report a computational method to improve efficiency of a de novo designed Kemp Eliminase enzyme KE15, by identifying mutations that enhance elec. fields and chem. positioning of the substrate that contribute to free energy stabilization of the transition state. Starting from the design that has a kcat/KM of 27 M-1s-1, the most improved variant introduced 4 computationally targeted mutations to yield a kcat/KM of 403 M-1s-1, with almost all of the enzyme improvement realized through a 43-fold improvement in kcat, indicative of a direct impact on the chem. step. This work raises the prospect of computationally designing enzymes that achieve better efficiency with more minimal exptl. intervention using elec. field optimization as guidance.
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    24. 24
      Stuyver, T.; Huang, J.; Mallick, D.; Danovich, D.; Shaik, S. TITAN: A Code for Modeling and Generating Electric Fields─Features and Applications to Enzymatic Reactivity. J. Comput. Chem. 2020, 41, 74– 82,  DOI: 10.1002/jcc.26072
      24
      TITAN: A Code for Modeling and Generating Electric Fields-Features and Applications to Enzymatic Reactivity
      Stuyver, Thijs; Huang, Jing; Mallick, Dibyendu; Danovich, David; Shaik, Sason
      Journal of Computational Chemistry (2020), 41 (1), 74-82CODEN: JCCHDD; ISSN:0192-8651. (John Wiley & Sons, Inc.)
      We present here a versatile computational code named "elec. fIeld generaTion And maNipulation (TITAN)," capable of generating various types of external elec. fields, as well as quantifying the local (or intrinsic) elec. fields present in proteins and other biol. systems according to Coulomb's Law. The generated elec. fields can be coupled with quantum mechanics (QM), mol. mechanics (MM), QM/MM, and mol. dynamics calcns. in most available software packages. The capabilities of the TITAN code are illustrated throughout the text with the help of examples. We end by presenting an application, in which the effects of the local elec. field on the hydrogen transfer reaction in cytochrome P 450 OleTJE enzyme and the modifications induced by the application of an oriented external elec. field are examd. We find that the protein matrix in P 450 OleTJE acts as a moderate catalyst and that orienting an external elec. field along the Fe-O bond of compd. I has the biggest impact on the reaction barrier. The induced catalysis/inhibition correlates with the calcd. spin d. on the O-atom. © 2019 Wiley Periodicals, Inc.
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    25. 25
      Shaik, S.; Danovich, D.; Dubey, K. D.; Stuyver, T. The Impact of Electric Fields on Chemical Structure and Reactivity. In Effects of Electric Fields on Structure and Reactivity: New Horizons in Chemistry; Shaik, S.; Stuyver, T., Eds.; Royal Society of Chemistry: Cambridge, 2021; Chapter 2, pp 12– 70.
      There is no corresponding record for this reference.
    26. 26
      (a) Luis, J. M.; Duran, M.; Andrés, J. L. A Systematic and Feasible Method for Computing Nuclear Contributions to Electrical Properties of Polyatomic Molecules. J. Chem. Phys. 1997, 107, 1501– 1512,  DOI: 10.1063/1.474503
      26a
      A systematic and feasible method for computing nuclear contributions to electrical properties of polyatomic molecules
      Luis, Josep M.; Duran, Miquel; Andres, Jose L.
      Journal of Chemical Physics (1997), 107 (5), 1501-1512CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      An analytic method to evaluate nuclear contributions to elec. properties (dipole moment, polarizability, hyperpolarizability) of polyat. mols. is presented. Such contributions control changes induced by an elec. field on equil. geometry (nuclear relaxation contribution) and vibrational motion (vibrational contribution) of a mol. system. Expressions to compute the nuclear contributions have been derived from a power series expansion of the potential energy. These contributions to the elec. properties are given in terms of energy derivs. with respect to normal coordinates, elec. field intensity or both. Only one calcn. of such derivs. at the field-free equil. geometry is required. To shown the useful efficiency of the anal. evaluation of elec. properties (the so-called AEEP method), results for calcns. on water and pyridine at the SCF/TZ2P and the MP2/TZ2P levels of theory are reported. The results obtained are compared with previous theor. calcns. and with exptl. values.
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      (b) Kirtman, B.; Luis, J. M.; Bishop, D. M. Simple Finite Field Method for Calculation of Static and Dynamic Vibrational Hyperpolarizabilities: Curvature Contributions. J. Chem. Phys. 1998, 108, 10008– 10012,  DOI: 10.1063/1.476460
      26b
      Simple finite field method for calculation of static and dynamic vibrational hyperpolarizabilities: Curvature contributions
      Kirtman, Bernard; Luis, Josep M.; Bishop, David M.
      Journal of Chemical Physics (1998), 108 (24), 10008-10012CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      In the static field limit, the vibrational hyperpolarizability consists of two contributions due to: (1) the shift in the equil. geometry (known as nuclear relaxation), and (2) the change in the shape of the potential energy surface (known as curvature). Simple finite field methods were previously developed for evaluating these static field contributions and also for detg. the effect of nuclear relaxation on dynamic vibrational hyperpolarizabilities in the infinite frequency approxn. In this paper the finite field approach is extended to include, within the infinite frequency approxn., the effect of curvature on the major dynamic nonlinear optical processes.
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      (c) Luis, J. M.; Martí, J.; Duran, M.; Andrés, J. L.; Kirtman, B. Nuclear Relaxation Contribution to Static and Dynamic (Infinite Frequency Approximation) Nonlinear Optical Properties by means of Electrical Property Expansions: Application to HF, CH4, CF4, and SF6. J. Chem. Phys. 1998, 108, 4123– 4130,  DOI: 10.1063/1.475810
      26c
      Nuclear relaxation contribution to static and dynamic (infinite frequency approximation) nonlinear optical properties by means of electrical property expansions: Application to HF, CH4, CF4, and SF6
      Luis, Josep M.; Marti, Josep; Duran, Miquel; Andres, Jose L.; Kirtman, Bernard
      Journal of Chemical Physics (1998), 108 (10), 4123-4130CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      Elec. property deriv. expressions are presented for the nuclear relaxation contribution to static and dynamic (infinite frequency approxn.) nonlinear optical properties. For CF4 and SF6, as opposed to HF and CH4, a term that is quadratic in the vibrational anharmonicity (and not previously evaluated for any mol.) makes an important contribution to the static 2nd vibrational hyperpolarizability of CF4 and SF6. A comparison between calcd. and exptl. values for the difference between the (anisotropic) Kerr effect and elec. field induced 2nd-harmonic generation shows that, at the Hartree-Fock level, the nuclear relaxation/infinite frequency approxn. gives the correct trend (in the series CH4, CF4, SF6) but is of the order of 50% too small.
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    27. 27
      (a) Torrent-Sucarrat, M.; Solà, M.; Duran, M.; Luis, J. M.; Kirtman, B. Initial Convergence of the Perturbation Series Expansion for Vibrational Nonlinear Optical Properties. J. Chem. Phys. 2002, 116, 5363– 5373,  DOI: 10.1063/1.1453953
      27a
      Initial convergence of the perturbation series expansion for vibrational nonlinear optical properties
      Torrent-Sucarrat, Miquel; Sola, Miquel; Duran, Miquel; Luis, Josep M.; Kirtman, Bernard
      Journal of Chemical Physics (2002), 116 (13), 5363-5373CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      Ab initio Hartree-Fock and MP2 calcns. of the longitudinal (hyper)polarizability - including the static electronic, static zero-point vibrational av. (ZPVA), and pure vibrational (static and dynamic) contributions - were carried out on a set of 7 typical medium size conjugated nonlinear optical (NLO) mols. The ZPVA is obtained through 1st-order in mech. plus elec. anharmonicity. Based on phys. nuclear relaxation considerations the individual (square bracket) terms that contribute to the pure vibrational (hyper)polarizability are then taken into account through 3rd-, 4th-, or 5th-order depending upon the type of term. In order to carry out the correlated treatment, field-induced coordinates and a special finite field technique are used. Correlation leads to very substantial differences in the abs. and relative values of the various contributions. In comparison to the electronic term the ZPVA correction is usually small but in 1 case is over 2/3 as large. Both static and dynamic pure vibrational contributions are commonly of a magnitude that is comparable to, or are larger than, the electronic term. The higher-order pure vibration terms are often large. For dynamic processes they can be almost as important as the lowest-order terms; for static (hyper)polarizabilities they can be more important. For typical NLO mols., the initial convergence behavior of the perturbation series in mech. and elec. anharmonicity requires further study.
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      (b) Torrent-Sucarrat, M.; Solà, M.; Duran, M.; Luis, J. M.; Kirtman, B. Basis Set and Electron Correlation Effects on ab Initio Electronic and Vibrational Nonlinear Optical Properties of Conjugated Organic Molecules. J. Chem. Phys. 2003, 118, 711– 718,  DOI: 10.1063/1.1521725
      27b
      Basis set and electron correlation effects on ab initio electronic and vibrational nonlinear optical properties of conjugated organic molecules
      Torrent-Sucarrat, Miquel; Sola, Miquel; Duran, Miquel; Luis, Josep M.; Kirtman, Bernard
      Journal of Chemical Physics (2003), 118 (2), 711-718CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      We have studied how the calcn. of electronic and vibrational contributions to nonlinear optical properties of three representative π-conjugated org. mols. is affected by the choice of basis set and the inclusion of electron correlation effects. The 6-31G basis does not always provide even qual. accuracy. For semiquant. accuracy a 6-31+G(d) basis is sufficient. Although, as compared to QCISD, a second-order Moller-Plesset (MP2) treatment often yields a substantial fraction of the electron correlation contribution, our MP2 results for the sep. electronic and vibrational terms are not consistently of semiquant. accuracy. Nevertheless, at the MP2 level the ratio between the vibrational and electronic contributions is satisfactorily reproduced.
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      (c) Torrent-Sucarrat, M.; Solà, M.; Duran, M.; Luis, J. M.; Kirtman, B. Basis Set and Electron Correlation Effects on Initial Convergence for Vibrational Nonlinear Optical Properties of Conjugated Organic Molecules. J. Chem. Phys. 2004, 120, 6346– 6355,  DOI: 10.1063/1.1667465
      27c
      Basis set and electron correlation effects on initial convergence for vibrational nonlinear optical properties of conjugated organic molecules
      Torrent-Sucarrat, Miquel; Sola, Miquel; Duran, Miquel; Luis, Josep M.; Kirtman, Bernard
      Journal of Chemical Physics (2004), 120 (14), 6346-6355CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      Using three typical π-conjugated mols. (1,3,5-hexatriene, 1-formyl-6-hydroxyhexa-1,3,5-triene, and 1,1-diamino-6,6-dinitrohexa-1,3,5-triene) we investigate the level of ab initio theory necessary to produce reliable values for linear and nonlinear optical properties, with emphasis on the vibrational contributions that are known to be important or potentially important. These calcns. are made feasible by employing field-induced coordinates in combination with a finite field procedure. For many, but not all, purposes the MP2/6-31+G(d) level is adequate. Based on our results the convergence of the usual perturbation treatment for vibrational anharmonicity was examd. Although this treatment is initially convergent in most circumstances, a problematic situation has been identified.
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      (d) Torrent-Sucarrat, M.; Luis, J. M.; Kirtman, B. Variational Calculation of Vibrational Linear and Nonlinear Optical Properties. J. Chem. Phys. 2005, 122, 204108  DOI: 10.1063/1.1909031
      27d
      Variational calculation of vibrational linear and nonlinear optical properties
      Torrent-Sucarrat, Miquel; Luis, Josep M.; Kirtman, Bernard
      Journal of Chemical Physics (2005), 122 (20), 204108/1-204108/10CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      A variational approach for reliably calcg. vibrational linear and nonlinear optical properties of mols. with large elec. and/or mech. anharmonicity is introduced. This approach utilizes a self-consistent soln. of the vibrational Schrodinger equation for the complete field-dependent potential-energy surface and, then, adds higher-level vibrational correlation corrections as desired. An initial application is made to static properties for three mols. of widely varying anharmonicity using the lowest-level vibrational correlation treatment (i.e., vibrational Moller-Plesset perturbation theory). Our results indicate when the conventional Bishop-Kirtman perturbation method can be expected to break down and when high-level vibrational correlation methods are likely to be required. Future improvements and extensions are discussed.
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    28. 28
      Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Petersson, G. A.; Nakatsuji, H.; Li, X.; Caricato, M.; Marenich, A. V.; Bloino, J.; Janesko, B. G.; Gomperts, R.; Mennucci, B.; Hratchian, H. P.; Ortiz, J. V.; Izmaylov, A. F.; Sonnenberg, J. L.; Williams; ; Ding, F.; Lipparini, F.; Egidi, F.; Goings, J.; Peng, B.; Petrone, A.; Henderson, T.; Ranasinghe, D.; Zakrzewski, V. G.; Gao, J.; Rega, N.; Zheng, G.; Liang, W.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Throssell, K.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M. J.; Heyd, J. J.; Brothers, E. N.; Kudin, K. N.; Staroverov, V. N.; Keith, T. A.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A. P.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Millam, J. M.; Klene, M.; Adamo, C.; Cammi, R.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Farkas, O.; Foresman, J. B.; Fox, D. J. Gaussian 16, revision C.01; Gaussian, Inc.: Wallingford, CT, 2016.
      There is no corresponding record for this reference.
    29. 29
      (a) Vosko, S. H.; Wilk, L.; Nusair, M. Accurate Spin-Dependent Electron Liquid Correlation Energies for Local Spin Density Calculations: a Critical Analysis. Can. J. Phys. 1980, 58, 1200– 1211,  DOI: 10.1139/p80-159
      29a
      Accurate spin-dependent electron liquid correlation energies for local spin density calculations: a critical analysis
      Vosko, S. H.; Wilk, L.; Nusair, M.
      Canadian Journal of Physics (1980), 58 (8), 1200-11CODEN: CJPHAD; ISSN:0008-4204.
      Various approx. forms for the correlation energy per particle of the spin-polarized homogeneous electron gas that have frequently been used in applications of the local spin d. approxn. to the exchange-correlation energy functional are assessed. By accurately recalcg. the RPA correlation energy as a function of electron d. and spin polarization, the inadequacies of the usual approxn. for interpolating between the para- and ferro-magnetic states are demonstrated and an accurate new interpolation formula is presented. A Pade approximant technique was used to accurately interpolate the recent Monte Carlo results. These results can be combined with the RPA spin-dependence so as to produce a correlation energy for a spin-polarized homogeneous electron gas with an estd. max. error of 1 mRy and thus should reliably det. the magnitude of non-local corrections to the local spin d. approxn. in real systems.
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      (b) Lee, C.; Yang, W.; Parr, R. G. Development of the Colle-Salvetti Correlation-Energy Formula into a Functional of the Electron Density. Phys. Rev. B 1988, 37, 785– 789,  DOI: 10.1103/PhysRevB.37.785
      29b
      Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density
      Lee, Chengteh; Yang, Weitao; Parr, Robert G.
      Physical Review B: Condensed Matter and Materials Physics (1988), 37 (2), 785-9CODEN: PRBMDO; ISSN:0163-1829.
      A correlation-energy formula due to R. Colle and D. Salvetti (1975), in which the correlation energy d. is expressed in terms of the electron d. and a Laplacian of the 2nd-order Hartree-Fock d. matrix, is restated as a formula involving the d. and local kinetic-energy d. On insertion of gradient expansions for the local kinetic-energy d., d.-functional formulas for the correlation energy and correlation potential are then obtained. Through numerical calcns. on a no. of atoms, pos. ions, and mols., of both open- and closed-shell type, it is demonstrated that these formulas, like the original Colle-Salvetti formulas, give correlation energies within a few percent.
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      (c) Becke, A. D. Density-Functional Thermochemistry. III. The Role of Exact Exchange. J. Chem. Phys. 1993, 98, 5648– 5652,  DOI: 10.1063/1.464913
      29c
      Density-functional thermochemistry. III. The role of exact exchange
      Becke, Axel D.
      Journal of Chemical Physics (1993), 98 (7), 5648-52CODEN: JCPSA6; ISSN:0021-9606.
      Despite the remarkable thermochem. accuracy of Kohn-Sham d.-functional theories with gradient corrections for exchange-correlation, the author believes that further improvements are unlikely unless exact-exchange information is considered. Arguments to support this view are presented, and a semiempirical exchange-correlation functional (contg. local-spin-d., gradient, and exact-exchange terms) is tested for 56 atomization energies, 42 ionization potentials, 8 proton affinities, and 10 total at. energies of first- and second-row systems. This functional performs better than previous functionals with gradient corrections only, and fits expt. atomization energies with an impressively small av. abs. deviation of 2.4 kcal/mol.
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    30. 30
      Ditchfield, R.; Hehre, W. J.; Pople, J. A. Self-Consistent Molecular-Orbital Methods. IX. An Extended Gaussian-Type Basis for Molecular-Orbital Studies of Organic Molecules. J. Chem. Phys. 1971, 54, 724– 728,  DOI: 10.1063/1.1674902
      30
      Self-consistent molecular-orbital methods. IX. Extended Gaussian-type basis for molecular-orbital studies of organic molecules
      Ditchfield, R.; Hehre, Warren J.; Pople, John A.
      Journal of Chemical Physics (1971), 54 (2), 724-8CODEN: JCPSA6; ISSN:0021-9606.
      An extended basis set of at. functions expressed as fixed linear combinations of Gaussian functions is presented for H and the first-row atoms C to F. In this set. described as 4-31 G, each inner shell is represented by a single basis function taken as a sum of 4 Gaussians, and each valence orbital is split into inner and outer parts described by 3 and 1 Gaussian function, resp. The expansion coeffs. and Gaussian exponents are detd. by minimizing the total calcd. energy of the at. ground state. This basis set is then used in single-determinant MO studies of a group of small polyat. mols. Optimization of valence-shell scaling factors shows that considerable rescaling of at. functions occurs in mols., the largest effects being obsd. for H and C. However, the range of optimum scale factors for each atom is small enough to allow the selection of a std. mol. set. The use of this std. basis gives theoretical equil. geometries in reasonable agreement with expt.
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    31. 31
      Grimme, S.; Antony, J.; Ehrlich, S.; Krieg, H. A Consistent and Accurate ab Initio Parametrization of Density Functional Dispersion Correction (DFT-D) for the 94 Elements H-Pu. J. Chem. Phys. 2010, 132, 154104  DOI: 10.1063/1.3382344
      31
      A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu
      Grimme, Stefan; Antony, Jens; Ehrlich, Stephan; Krieg, Helge
      Journal of Chemical Physics (2010), 132 (15), 154104/1-154104/19CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      The method of dispersion correction as an add-on to std. Kohn-Sham d. functional theory (DFT-D) has been refined regarding higher accuracy, broader range of applicability, and less empiricism. The main new ingredients are atom-pairwise specific dispersion coeffs. and cutoff radii that are both computed from first principles. The coeffs. for new eighth-order dispersion terms are computed using established recursion relations. System (geometry) dependent information is used for the first time in a DFT-D type approach by employing the new concept of fractional coordination nos. (CN). They are used to interpolate between dispersion coeffs. of atoms in different chem. environments. The method only requires adjustment of two global parameters for each d. functional, is asymptotically exact for a gas of weakly interacting neutral atoms, and easily allows the computation of at. forces. Three-body nonadditivity terms are considered. The method has been assessed on std. benchmark sets for inter- and intramol. noncovalent interactions with a particular emphasis on a consistent description of light and heavy element systems. The mean abs. deviations for the S22 benchmark set of noncovalent interactions for 11 std. d. functionals decrease by 15%-40% compared to the previous (already accurate) DFT-D version. Spectacular improvements are found for a tripeptide-folding model and all tested metallic systems. The rectification of the long-range behavior and the use of more accurate C6 coeffs. also lead to a much better description of large (infinite) systems as shown for graphene sheets and the adsorption of benzene on an Ag(111) surface. For graphene it is found that the inclusion of three-body terms substantially (by about 10%) weakens the interlayer binding. We propose the revised DFT-D method as a general tool for the computation of the dispersion energy in mols. and solids of any kind with DFT and related (low-cost) electronic structure methods for large systems. (c) 2010 American Institute of Physics.
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    32. 32
      (a) Johnson, E. R.; Becke, A. D. A Post-Hartree-Fock Model of Intermolecular Interactions: Inclusion of Higher-Order Corrections. J. Chem. Phys. 2006, 124, 174104  DOI: 10.1063/1.2190220
      32a
      A post-Hartree-Fock model of intermolecular interactions: Inclusion of higher-order corrections
      Johnson, Erin R.; Becke, Axel D.
      Journal of Chemical Physics (2006), 124 (17), 174104/1-174104/9CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      We have previously demonstrated that the dipole moment of the exchange hole can be used to derive intermol. C6 dispersion coeffs. [J. Chem. Phys. 122, 154104 (2005)]. This was subsequently the basis for a novel post-Hartree-Fock model of intermol. interactions [J. Chem. Phys. 123, 024101 (2005)]. In the present work, the model is extended to include higher-order dispersion coeffs. C8 and C10. The extended model performs very well for prediction of intermonomer sepns. and binding energies of 45 van der Waals complexes. In particular, it performs twice as well as basis-set extrapolated MP2 theory for dispersion-bound complexes, with minimal computational cost.
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      (b) Grimme, S.; Ehrlich, S.; Goerigk, L. Effect of the Damping Function in Dispersion Corrected Density Functional Theory. J. Comput. Chem. 2011, 32, 1456– 1465,  DOI: 10.1002/jcc.21759
      32b
      Effect of the damping function in dispersion corrected density functional theory
      Grimme, Stefan; Ehrlich, Stephan; Goerigk, Lars
      Journal of Computational Chemistry (2011), 32 (7), 1456-1465CODEN: JCCHDD; ISSN:0192-8651. (John Wiley & Sons, Inc.)
      It is shown by an extensive benchmark on mol. energy data that the math. form of the damping function in DFT-D methods has only a minor impact on the quality of the results. For 12 different functionals, a std. "zero-damping" formula and rational damping to finite values for small interat. distances according to Becke and Johnson (BJ-damping) has been tested. The same (DFT-D3) scheme for the computation of the dispersion coeffs. is used. The BJ-damping requires one fit parameter more for each functional (three instead of two) but has the advantage of avoiding repulsive interat. forces at shorter distances. With BJ-damping better results for nonbonded distances and more clear effects of intramol. dispersion in four representative mol. structures are found. For the noncovalently-bonded structures in the S22 set, both schemes lead to very similar intermol. distances. For noncovalent interaction energies BJ-damping performs slightly better but both variants can be recommended in general. The exception to this is Hartree-Fock that can be recommended only in the BJ-variant and which is then close to the accuracy of cor. GGAs for non-covalent interactions. According to the thermodn. benchmarks BJ-damping is more accurate esp. for medium-range electron correlation problems and only small and practically insignificant double-counting effects are obsd. It seems to provide a phys. correct short-range behavior of correlation/dispersion even with unmodified std. functionals. In any case, the differences between the two methods are much smaller than the overall dispersion effect and often also smaller than the influence of the underlying d. functional. © 2011 Wiley Periodicals, Inc.; J. Comput. Chem., 2011.
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    33. 33
      (a) Perdew, J. P. Density-Functional Approximation for the Correlation Energy of the Inhomogeneous Electron Gas. Phys. Rev. B 1986, 33, 8822– 8824,  DOI: 10.1103/PhysRevB.33.8822
      33a
      Density-functional approximation for the correlation energy of the inhomogeneous electron gas
      Perdew
      Physical review. B, Condensed matter (1986), 33 (12), 8822-8824 ISSN:0163-1829.
      There is no expanded citation for this reference.
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      (b) Becke, A. D. Density-Functional Exchange-Energy Approximation with Correct Asymptotic Behavior. Phys. Rev. A 1988, 38, 3098– 3100,  DOI: 10.1103/PhysRevA.38.3098
      33b
      Density-functional exchange-energy approximation with correct asymptotic behavior
      Becke, A. D.
      Physical Review A: Atomic, Molecular, and Optical Physics (1988), 38 (6), 3098-100CODEN: PLRAAN; ISSN:0556-2791.
      Current gradient-cor. d.-functional approxns. for the exchange energies of at. and mol. systems fail to reproduce the correct 1/r asymptotic behavior of the exchange-energy d. A gradient-cor. exchange-energy functional is given with the proper asymptotic limit. This functional, contg. only one parameter, fits the exact Hartree-Fock exchange energies of a wide variety of at. systems with remarkable accuracy, surpassing the performance of previous functionals contg. two parameters or more.
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    34. 34
      Murgida, D. H.; Hildebrandt, P. Electron-Transfer Processes of Cytochrome c at Interfaces. New Insights by Surface-Enhanced Resonance Raman Spectroscopy. Acc. Chem. Res. 2004, 37, 854– 861,  DOI: 10.1021/ar0400443
      34
      Electron-Transfer Processes of Cytochrome c at Interfaces. New Insights by Surface-Enhanced Resonance Raman Spectroscopy
      Murgida, Daniel H.; Hildebrandt, Peter
      Accounts of Chemical Research (2004), 37 (11), 854-861CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
      A review. The heme protein cytochrome c acts as an electron carrier at the mitochondrial-membrane interface and thus exerts its function under the influence of strong elec. fields. To assess possible consequences of elec. fields on the redox processes of cytochrome c, the protein can be immobilized to self-assembled monolayers on electrodes and studied by surface-enhanced resonance Raman spectroscopy. Such model systems may mimic some essential features of biol. interfaces including local elec. field strengths. It is shown that physiol. relevant elec. field strengths can effectively modulate the electron-transfer dynamics and induce conformational transitions.
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    35. 35
      Dubey, K. D.; Stuyver, T.; Kalita, S.; Shaik, S. Solvent Organization and Rate Regulation of a Menshutkin Reaction by Oriented External Electric Fields are Revealed by Combined MD and QM/MM Calculations. J. Am. Chem. Soc. 2020, 142, 9955– 9965,  DOI: 10.1021/jacs.9b13029
      There is no corresponding record for this reference.
    36. 36
      Fernández, S.; Franco, F.; Casadevall, C.; Martin-Diaconescu, V.; Luis, J. M.; Lloret-Fillol, J. A Unified Electro- and Photocatalytic CO2 to CO Reduction Mechanism with Aminopyridine Cobalt Complexes. J. Am. Chem. Soc. 2020, 142, 120– 133,  DOI: 10.1021/jacs.9b06633
      36
      A Unified Electro- and Photocatalytic CO2 to CO Reduction Mechanism with Aminopyridine Cobalt Complexes
      Fernandez, Sergio; Franco, Federico; Casadevall, Carla; Martin-Diaconescu, Vlad; Luis, Josep M.; Lloret-Fillol, Julio
      Journal of the American Chemical Society (2020), 142 (1), 120-133CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      A mechanistic understanding of electro- and photocatalytic CO2 redn. is crucial to develop strategies to overcome catalytic bottlenecks. In this regard, for a new CO2-to-CO redn. cobalt aminopyridine catalyst, a detailed exptl. and theor. mechanistic study is herein presented toward the identification of bottlenecks and potential strategies to alleviate them. The combination of electrochem. and in situ spectroelectrochem. together with spectroscopic techniques led us to identify elusive key electrocatalytic intermediates derived from complex [LN4Co(OTf)2] (1) (LN4 = 1-[2-pyridylmethyl]-4,7-dimethyl-1,4,7-triazacyclononane) such as a highly reactive cobalt(I) (1(I)) and a cobalt(I) carbonyl (1(I)-CO) species. The combination of spectroelectrochem. studies under CO2, 13CO2, and CO with DFT disclosed that 1(I) reacts with CO2 to form the pivotal 1(I)-CO intermediate at the 1(II/I) redox potential. However, at this redn. potential, the formation of 1(I)-CO restricts the electrocatalysis due to the endergonicity of the CO release step. In agreement with the exptl. obsd. CO2-to-CO electrocatalysis at the CoI/0 redox potential, computational studies suggested that the electrocatalytic cycle involves striking metal carbonyls. In contrast, under photochem. conditions, the catalysis smoothly proceeds at the 1(II/I) redox potential. Under the latter conditions, it is proposed that the electron transfer to form 1(I)-CO from 1(II)-CO is under diffusion control. Then, the CO release from 1(II)-CO is kinetically favored, facilitating the catalysis. Finally, we have found that visible-light irradn. has a pos. impact under electrocatalytic conditions. We envision that light irradn. can serve as an effective strategy to circumvent the CO poisoning and improve the performance of CO2 redn. mol. catalysts.