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Subphthalocyanines Axially Substituted with a Tetracyanobuta-1,3-diene–Aniline Moiety: Synthesis, Structure, and Physicochemical Properties

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† Departamento de Química Orgánica, Universidad Autónoma de Madrid, 28049 Madrid, Spain
‡ IMDEA-Nanociencia, Campus de Cantoblanco, 28049 Madrid, Spain
§ Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, 28049 Madrid, Spain
⊥ Department of Chemistry and Pharmacy, Interdisciplinary Center for Molecular Materials (ICMM), Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen, Germany
*[email protected]
*[email protected]
*[email protected]
Cite this: J. Am. Chem. Soc. 2017, 139, 15, 5520–5529
Publication Date (Web):March 21, 2017
https://doi.org/10.1021/jacs.7b01460

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Abstract

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A 1,1,4,4-tetracyanobuta-1,3-diene (TCBD)–aniline moiety has been introduced, for the first time, at the axial position of two subphthalocyanines (SubPcs) peripherally substituted with hydrogen (H12SubPc) or fluorine atoms (F12SubPc). Single-crystal X-ray analysis of both SubPc–TCBD–aniline systems showed that each conjugate is a racemic mixture of two atropisomers resulting from the almost orthogonal geometry adopted by the axial TCBD unit, which were separated by chiral high-performance liquid chromatography. Remarkably, the single-crystal X-ray structure of one atropisomer of each SubPc–TCBD–aniline conjugate has been solved, allowing to unambiguously assign the atropisomers’ absolute configuration, something, to the best of our knowledge, unprecedented in TCBD-based conjugates. Moreover, the physicochemical properties of both SubPc–TCBD–aniline racemates have been investigated using a wide range of electrochemical as well as steady-state and time-resolved spectroscopic techniques. Each of the two SubPc–TCBD–aniline conjugates presents a unique photophysical feature never observed before in SubPc chemistry. As a matter of fact, H12SubPc–TCBD–aniline showed significant ground-state charge transfer interactions between the H12SubPc macrocycle and the electron-withdrawing TCBD unit directly attached at its axial position. In contrast, F12SubPc–TCBD–aniline gave rise to an intense, broad emission, which red shifts upon increasing the solvent polarity and stems from an excited complex (i.e., an exciplex). Such an exciplex emission, which has also no precedent in TCBD chemistry, results from intramolecular interactions in the excited state between the electron-rich aniline and the F12SubPc π-surface, two molecular fragments kept in spatial proximity by the “unique” three-dimensional geometry adopted by the F12SubPc–TCBD–aniline. Complementary transient absorption studies were carried out on both SubPc–TCBD–aniline derivatives, showing the occurrence, in both cases, of photoinduced charge separation and corroborating the formation of the aforementioned intramolecular exciplex in terms of a radical ion pair stabilized through-space.

Introduction

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During the past decades, the preparation and study of light-responsive electron donor–acceptor (D–A) systems have gained increasing interest. Controlling electron transfer, one of the primary events responsible for the conversion of solar energy into chemical energy in natural photosynthetic systems, (1) and understanding the factors that ultimately govern such process are fundamental issues. These need to be addressed for profiting from these conjugates in technologically relevant fields related to light-to-energy conversion and organic electronics. (2)
Among the molecular building blocks used for the construction of such light-powered, electroactive ensembles, subphthalocyanines (SubPcs) hold a privileged position due to their outstanding photophysical properties. These singular cone-shaped, aromatic molecules show a strong absorption in the 550–650 nm region with excitation energies above 2.0 eV, high fluorescence quantum yields, a rich redox chemistry, and low reorganization energies. (3) To date, several SubPc-based architectures have been prepared, in which the macrocycle has been connected, either covalently through functionalization at the SubPc’s peripheral and/or axial positions or via supramolecular interactions, to electroactive moieties such as fullerenes, (4) ferrocenes, (5) porphyrins, (6) or phthalocyanines. (6a, 7) In these systems, the SubPc can act as electron donor or acceptor, depending on the macrocycle’s redox features, which are mostly determined by the nature of its peripheral substituents and the redox properties of its electroactive partner. For most of these SubPc-based D–A ensembles, photophysical studies in solution have shown the occurrence of photoinduced electron transfer resulting in the formation of intra- or intermolecular charge-separated species. Moreover, some SubPc-containing D–A couples have also been incorporated in organic solar cells showing excellent photovoltaic performances. (8)
As part of our systematic investigation of the preparation and study of novel SubPc-based D–A systems, we decided to use 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) as a partner for SubPcs. TCBD is a cyano-rich moiety, which, in the past, has been covalently linked to electroactive units such as anilines, (9) porphyrins, (10) corannulenes, (11) or phthalocyanines. (12) In most of these TCBD-based D–A conjugates, photoinduced energy and electron transfer has been observed, resulting from the coupling between the strong electron-accepting TCBD and its electron-rich counterpart. Besides its remarkable electron-withdrawing features, TCBD also exhibits some interesting structural features, namely, a quasi-orthogonal arrangement of its two dicyanovinyl (DCV) halves (9) and the restricted rotation around the C2–C3 carbon bond of the TCBD moiety, which results in the formation of atropisomers. (13)
In light of the aforementioned, we report here on the preparation and study of two novel derivatives, in which a TCBD–aniline moiety has been introduced, for the first time, at the axial position of two SubPcs peripherally substituted with hydrogen (H12SubPc) or fluorine atoms (F12SubPc). Each of the two SubPc–TCBD–aniline conjugates is de facto a racemic mixture of two atropisomers, which are also enantiomers that have been separated using chiral high-performance liquid chromatography (HPLC). Interestingly, the X-ray crystal structure of one atropisomer of each SubPc–TCBD–aniline conjugate was determined, allowing us to unambiguously assign the atropisomers’ absolute configuration, which is, to the best of our knowledge, unprecedented in TCBD-based conjugates. Moreover, the two SubPc–TCBD–aniline conjugates present some unusual photophysical features as corroborated in steady-state and time-resolved spectroscopic assays. On one hand, strong ground-state charge transfer interactions occur between H12SubPc and its axially substituted TCBD ligand in H12SubPc–TCBD–aniline. On the other hand, an intense exciplex emission resulting from the intramolecular π-stacking between the electron-rich aniline and the π-deficient F12SubPc surface is observed for its perfluorinated analogue. Both features, which have never been observed in any SubPc derivative before, are a consequence of the unique three-dimensional geometry adopted by the SubPc–TCBD–aniline conjugates and the different redox features of the H12SubPc and F12SubPc macrocycles.

Results and Discussion

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Synthesis, X-ray Diffraction, Chiral HPLC, and Circular Dichroism Studies

SubPc–TCBD–aniline conjugates 1 and 2 were prepared in a two-step synthesis starting from SubPc–Cl 5 and 6, respectively. In these SubPcs, the replacement of the axial chlorido ligand at the boron atom was readily achieved by their reaction with the Grignard of 4-ethynyl-N,N′-dimethylaniline (14) to give SubPc–ethynyl–aniline derivatives 3 and 4, respectively. Subsequent cycloaddition–retroelectrocyclization (CA–RE) reaction of the alkynyl-functionalized SubPcs with tetracyanoethylene afforded SubPc–TCBD–aniline conjugates 1 and 2, respectively, in excellent yields (Scheme 1).

Scheme 1

Scheme 1. Synthesis of SubPc–TCBD–Aniline Conjugates 1 and 2a
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Scheme aConditions: (i) 4-ethynyl-N,N′-dimethylaniline, EtMgBr, anhydrous THF, 60 °C; (ii) tetracyanoethylene, anhydrous THF, room temperature.

Conjugates 1 and 2 as well as precursors 3–6 were fully characterized by a wide range of spectroscopic, spectrometric, and electrochemical techniques (see Supporting Information). In the case of SubPc–TCBD–aniline conjugates 1 and 2, single crystals suitable for X-ray diffraction analysis were obtained by slow diffusion of n-hexane into a chloroform solution of the corresponding SubPc derivative. (15) The crystal structures of 1 and 2 show that, in both derivatives, the axial TCBD unit is highly nonplanar, as previously observed in other TCBD-based compounds. (9) The torsion angle (ϑ) between the four carbon atoms, which constitute the butadiene backbone, is close to 85° (Figures S3.1 and S3.7, respectively). As a consequence of the nonplanar geometry adopted by the two DCV moieties of the TCBD unit, two atropisomers are formed both in 1 and 2, namely, Ra-1 and Sa-1 (Figure S3.1), and Ra-2 (Figure 1a) and Sa-2 (Figure 1b), respectively (see section 4 in the Supporting Information). An interesting feature of the crystal structure of 1 and 2 is the vicinal and quasi-parallel arrangement adopted by one of the SubPc isoindole units with respect to the aniline moiety at the macrocycle’s axial position (Figures S3.1 and S3.7, respectively). This geometrical feature is important to rationalize some of the photophysical behaviors of these conjugates (vide infra). Although SubPc–TCBD–aniline conjugates 1 and 2 possess similar geometrical features in terms of their molecular structure, they show a significantly different crystal packing. H12SubPc–TCBD–aniline 1 organizes in the form of heterochiral Ra-1/Sa-1 dimers through π-stacking, concave–concave SubPc interactions (Figure S3.2). Additionally, each H12SubPc–TCBD–aniline in the dimer gives rise to two CN···H(aniline aryl ring) interactions with another molecule of opposite chirality of a vicinal dimer (Figure S3.3). In contrast, the two atropisomers of F12SubPc–TCBD–aniline 2 are arranged in a concave–convex fashion, forming heterochiral columnar stacks (Figure S3.8), which run both parallel (Figure S3.9) and antiparallel (Figure S3.10a) between them. For each SubPc in the column, stabilizing intermolecular N···B interactions between stacked SubPcs of opposite chirality are discernible. In addition, π-stacking, F···H(aniline methyl group), and CN···H(aniline methyl group) interactions between F12SubPc–TCBD–aniline molecules belonging to vicinal antiparallel columns are observed in the crystal structure (Figure S3.10b). A similar solid-state arrangement of F12SubPc and H12SubPc derivatives, forming columnar and dimeric structures, respectively, has previously been observed. (16)

Figure 1

Figure 1. Lateral view (with respect to the SubPc–TCBD–aniline B–C bond) of the X-ray crystal structure of atropisomers (a) Ra-2 and (b) Sa-2 in F12SubPc–TCBD–aniline racemate 2. Lateral (top) and top view (bottom) (with respect to the SubPc–TCBD–aniline B–C bond) of the X-ray crystal structure of atropisomers (c) Sa-1 and (d) Ra-2 (for a detailed account on how to determine the atropisomers’ absolute configuration, see section 4 in the Supporting Information). In the top view representations, in order to facilitate the visualization of the atropisomers, (i) one of the two atropisomers was colored in red (in b), and (ii) solid colors have been used to fill the SubPcs (light red in b, light blue in b and c) and the aniline ring (light purple). Carbon atoms are in light blue, nitrogen atoms in dark blue, boron atoms in light pink, hydrogen atoms in white, and fluorine atoms in yellow. In (c), chloroform molecules of crystallization have been omitted for clarity.

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The separation of axially chiral Sa and Ra atropisomers from a racemic mixture of SubPc–TCBD–aniline 1 and 2 was achieved by using semipreparative chiral HPLC (Figures S5.1, and 2a and S5.2, respectively). The mirror-image circular dichroism (CD) spectra of the isolated atropisomers of 1 (Figure S6.1) and 2 (Figures 2b and S6.2) provide conclusive evidence of the enantiomeric relationship between the Sa and Ra species. (17) Single crystals grown out of one of the two isolated atropisomers of SubPc–TCBD–aniline 1 (blue trace in Figure S5.1) and 2 (red trace in Figure 2a) were obtained, corresponding to atropisomers Sa-1 (Figure S3.4) and Ra-2 (Figure S3.11), respectively. (15) The X-ray crystal structure of the enantiopure atropisomers shows that, at the molecular level, they share, as expected, important structural similarities with Sa-1 and Ra-2 in racemates 1 and 2, respectively. However, the crystal packing of enantiopure Sa-1 and Ra-2 bears appreciable differences relative to those of the racemic mixtures. A close look at the three-dimensional crystal structure of Sa-1 shows that this atropisomer forms Sa-1/Sa-1 dimers (Figures 1c and S3.5). Compared to the heterochiral Ra-1/Sa-1 dimers in racemate 1, they feature (i) longer SubPc-to-SubPc distances (4.26 vs 3.74 Å) and (ii) a different packing arrangement (Figure S3.6). For atropisomer Ra-2, its crystal packing shows the formation of columnar structures (Figures 1d and S3.12), which run both parallel (Figure S3.13) and antiparallel (Figure S3.14a) between them, as observed for racemate 2. A comparison of the solid-state arrangement of atropisomer Ra-2 and racemate 2 indicates, in the former, (i) a more straight alignment of the SubPc macrocycles within the columns, (ii) a shorter intermolecular CN···B distance between stacked F12SubPc–TCBD–aniline (3.32 vs 3.72 Å), and (iii) a different packing arrangement (Figure S3.14b). While few examples of X-ray crystal structures of TCBD-based racemates have been reported to date, (18) this is the first time that, to the best of our knowledge, the absolute configuration of enantiopure samples of TCBD-based atropisomers, such as Sa-1 and Ra-2, has been unequivocally determined.

Figure 2

Figure 2. (a) HPLC chromatogram of F12SubPc–TCBD–aniline racemate 2 with peaks corresponding to atropisomers Sa-2 (blue trace) and Ra-2 (red trace). The area underneath the blue and red traces is 50.2 and 49.8%, respectively. (b) Circular dichroism spectra of atropisomers Sa-2 (blue spectrum) and Ra-2 (red spectrum) in CHCl3 (atropisomers’ concentration = 3.5 × 10–5 M).

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Photophysical and Electrochemical Studies

UV/Vis Absorption Studies

The absorption features of SubPc–TCBD–aniline conjugates 1 and 2 (Figure 3a,b) and SubPc precursors 3–6 (Figure S10.1) were then investigated. The absorption spectra of SubPc–ethynyl–aniline conjugates 3 and 4 in toluene are dominated by distinct Q-band absorptions at 567/576 nm, respectively, along with less intense Soret band absorptions at 304/303 nm, respectively. The similarity between the absorption spectra of SubPc–ethynyl–aniline conjugates 3 and 4 and the ones of SubPc–Cl 5 and 6 suggests negligible ground-state interactions between the SubPc and the axial ethynyl–aniline moiety (Figure S10.1 and Table S10.1). In contrast, and to our surprise, the absorption spectra of SubPc–TCBD–aniline conjugates 1 and 2 showed significant differences with respect to the spectra of their respective SubPc precursors (Figure S10.1). For 1 and 2, characteristic Soret and Q-band absorptions are noted at 303/315 and 587/598 nm, respectively. The latter bands are bathochromically shifted (∼22 nm) and slightly broadened with respect to the Q-band absorptions of their precursors 3 and 4. The significant red shift in 1 and 2 is especially remarkable considering that, in the SubPcs, the position of the Q-band absorption is mainly dictated by the nature of the peripheral substituents and is only slightly influenced by changes in the axial ligand. (19) To rule out that any of the aforementioned trends are associated with the aggregation of 1 or 2 in solution, dilution assays in toluene were performed (Figures S10.5 and S10.6, respectively). The lack of any appreciable changes upon dilution, as far as the position and shape of the main absorptions is concerned, leads us to conclude that the aforementioned Q-band red shifts observed in 1 and 2 are due to intramolecular electronic communications between the SubPc and the axial TCBD moiety in the ground state rather than intermolecular electronic effects.

Figure 3

Figure 3. Normalized steady-state absorption (black) and fluorescence spectra (red) of (a) H12SubPc–TCBD–aniline conjugate 1 (λex = 530 nm, c = 2.05 × 10–6 M) and (b) F12SubPc–TCBD–aniline conjugate 2 (λex = 550 nm, c = 8.90 × 10–6 M) recorded in toluene.

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Beside the SubPc Soret and Q-bands, an additional absorption feature is noted for 1 and 2 at 440 and 461 nm, respectively. Valuable insights into the nature of these absorptions came from analyzing the absorption spectrum of TCBD–aniline derivative 7 (see Supporting Information for its structure): A broad absorption is maximized at 463 nm with a shoulder at 410 nm (Figure S10.2). Such transitions are attributable to a charge transfer (CT) absorption resulting from ground-state interactions between the electron-donating aniline and the electron-withdrawing TCBD (Figure S7.1), similarly to what is observed in analogous TCBD–aniline derivatives. (10a, 20) The CT nature of this transition was further confirmed by positive solvatochromism, resulting in a red shift of the absorption maximum moving from toluene (463 nm) to a more polar solvent such as benzonitrile (477 nm) (Table S10.1). Similarly to 7, conjugates 1 and 2 show a bathochromic shift of the TCBD–aniline-based absorptions upon increasing the solvent polarity (i.e., 440/461 nm in toluene and 459/473 nm in benzonitrile) (Figures S10.3a and S10.4a, and Table S10.1). (12) In light of the aforementioned results, these transitions relate to the ground-state absorption of the highly polarized TCBD–aniline fragment. A closer look at the solvent-dependent absorption spectra of 1 reveals a slight broadening in the low-energy transition upon increasing the solvent polarity (Figure S10.3b). A possible rationale includes an underlying ground CT state between the electron-donating SubPc and the electron-withdrawing TCBD (vide infra). In stark contrast, the Q-band absorption in F12SubPc–TCBD–aniline 2 lacks any dependence on the solvent polarity (Figure S10.4b). We conclude a lack of ground-state CT interactions between SubPc and TCBD, probably due to the electron-withdrawing nature of the fluorinated SubPc (Figure S10.4b).

Fluorescence Studies

Next, fluorescence studies with 1–4 were carried out, and the most relevant data are summarized in Table S10.2. The fluorescence spectra of SubPc–ethynyl–aniline conjugates 3 and 4 in toluene evolve as mirror images of the respective absorption spectra with maxima at 574 and 583 nm, respectively, and small Stokes shifts of 7 nm (Figure S10.7). However, significant differences between 3 and 4 were observed in terms of their fluorescence quantum yield (ΦF). For 3, its ΦF in toluene (0.16) is nearly identical to that of SubPc reference compound 8 (0.17) (see Supporting Information for its structure), whereas it significantly decreases to 5 × 10–3 in benzonitrile, that is, a fluorescence quenching of about 97% (Table S10.2). In contrast, ΦF of 4 ranges from 2 × 10–4 (toluene) to 1.4 × 10–3 (chlorobenzene), which correlates with a fluorescence quenching of more than 99%. A singlet excited-state energy of aniline, which is higher (4.30 eV) (21) than that of the SubPc (2.17 and 2.14 eV in 3 and 4, respectively), (22) renders an energy transfer unfeasible. Thus, we assume that the observed fluorescence quenching of 3 (in a polar solvent such as benzonitrile) and 4 (in all the investigated solvents, independently on their polarity) is due to an intramolecular charge separation (CS). In line with this conclusion, the stronger quenching in 4 in low polar solvents is rationalized on the basis that F12SubPc is a much stronger electron acceptor than H12SubPc, resulting in more favorable CS thermodynamics than in 3.
Turning to H12SubPc–TCBD–aniline 1, we see that its fluorescence spectrum is dominated by a maximum at 584 nm (Figure 3a). Notably, an “inverted” Stokes shift of 3 nm is derived when comparing the SubPc Q-band absorption and fluorescence maxima. To shed light on such unusual behavior, an excitation spectrum of 1 (λem = 630 nm) was recorded in toluene (Figure 4a). A comparison between the excitation and absorption spectra of 1 reveals (i) a hypsochromic shift (15 nm) of the SubPc Q-band absorption in the former spectrum and (ii) a negligible contribution from the TCBD–aniline CT band to the emission at 630 nm. Conversely, the excitation Q-band absorption of 1 matches quite well, both in its position and shape, to those of precursors H12SubPc–ethynyl–aniline 3 and H12SubPc–Cl 5 (Figure S10.9b). (23) Worthy of notice is also the red shift (12 nm) observed when comparing the SubPc excitation and emission band maxima of 1 (Figure S10.9a). At this point, we hypothesize that the SubPc Q-band absorption in 1 results from an overlap of two transitions, namely, a “pure” SubPc Q-band and a CT absorption band. We believe that a push–pull effect between SubPc and TCBD in 1, as already postulated in the context of the solvent-dependent absorption studies (vide supra), is responsible for such CT. Further support for this hypothesis comes from the quenching of ΦF of 1, when going from toluene (7.7 × 10–3) to a more polar solvent such as benzonitrile (6 × 10–4) (Table S10.2).

Figure 4

Figure 4. Normalized steady-state absorption (black) and excitation spectra (red) of (a) H12SubPc–TCBD–aniline conjugate 1 (λem = 630 nm, c = 1.09 × 10–6 M) and (b) F12SubPc–TCBD–aniline conjugate 2 (λem = 680 nm, c = 1.09 × 10–6 M) recorded in toluene.

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To our surprise, the fluorescence of F12SubPc–TCBD–aniline 2 differs significantly with respect to that of the structurally analogous 1. Its fluorescence spectrum in toluene is dominated by a broad, featureless low-energy band maximizing at 675 nm and a shoulder at around 612 nm, emission bands which are red-shifted by 77 and 14 nm, respectively, relative to the SubPc Q-band absorption (Figure 3b). Insights into the origin of such a dual fluorescence came from solvent-dependent studies (Figure S10.10a,b). On one hand, a strong quenching (>99%) and a large red shift (35 nm) of the intense, lower-energy emission band are observed upon increasing the solvent polarity from toluene to benzonitrile (Table S10.2). On the other hand, negligible changes were noted in the position of the high-energy emission at around 612 nm upon increasing the solvent polarity. The solvent independence and the relatively small Stokes shift of 14 nm suggest that the latter fluorescence stems from a nonpolar excited state, such as the locally excited SubPc state. Turning to the broad and featureless low-energy emission, which can be detected in toluene by the naked eye (Figure S10.10c), the strong positive solvatochromism and the intense fluorescence quenching upon increasing the solvent polarity infer a “polarized” excited state. These findings, together with the lack of any ground CT state absorptions (vide supra), point out the formation of an excited complex (i.e., an exciplex). This species results from the electrostatic interactions between closely spaced electron donors (D) and electron acceptors (A) in their excited and ground states through a partial CT (see section 11 in the Supporting Information). (24, 25) Excitation studies (λem = 680 nm) further supported the exciplex hypothesis. In contrast to 1, the excitation spectrum of 2 strongly resembles its absorption spectrum (Figure 4b). In other words, regardless of photoexciting the SubPc Q-band or the TCBD–aniline CT band, a radiative state is generated. As a matter of fact, we hypothesize that ground-state and excited-state interactions between the SubPc and the TCBD–aniline moiety are involved. Decisive support for the exciplex hypothesis comes from the X-ray crystal structure of 2, which shows that the aniline is arranged nearly parallel and at short distances (i.e., ∼4.0 Å) with respect to F12SubPc (vide supra) (Figure 1a,b). As a result, an intramolecular orbital overlap between the electron-rich aniline and the electron-accepting F12SubPc can occur in the excited state, giving rise to a partial CT from the D to the A, that is, a [(SubPc–TCBD)δ−–anilineδ+]* species (vide infra).
Additionally, temperature-dependent fluorescence studies were carried out with the aim of investigating in 2 the effect of the temperature on the SubPc local and exciplex emission. Fluorescence measurements in chlorobenzene and toluene, where both emissive features are distinguishable, show that upon increasing the temperature from 5 to 65 °C the localized SubPc fluorescence remains constant at 612 nm (inset Figure 5 and Figure S10.12b). Conversely, its intensity increases by a factor of 4 in both solvents (Figures 5 and S10.12a). Concomitantly, a decrease of the exciplex emission relative to the SubPc localized fluorescence is observed (inset Figure 5 and Figure S10.12b) together with a blue-shifting exciplex emission maximum (∼32 nm in chlorobenzene and ∼24 nm in toluene). The hypsochromic shift upon increasing the temperature has already been observed for other D–A conjugates and rationalized on the basis of a destabilization of the polarized exciplex state. (26) Such changes are triggered by temperature-induced changes in the conformation of the compound and/or viscosity and dielectric constant of the solvent. The presence of an isoemissive point at ∼710 nm in chlorobenzene and ∼712 nm in toluene (Figures 5 and S10.12a, respectively) suggests that the two emissive processes are somehow linked to each other. At this point, we have no clear understanding regarding the factors that govern/influence the interplay between the SubPc localized and exciplex excited states. Further studies are needed in order to shed light on this singular behavior. The temperature dependence seen for 2 is fully reversible, and the original emission spectra in chlorobenzene and toluene are recovered upon cooling back to 5 °C.

Figure 5

Figure 5. Fluorescence and (inset) normalized (with respect to the SubPc local emission at 612 nm) fluorescence spectra of F12SubPc–TCBD–aniline conjugate 2 (λex = 550 nm, c = 2.0 × 10–5 M) recorded upon heating up from 5 to 65 °C in chlorobenzene.

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A different behavior was noted in temperature-dependent studies with H12SubPc–TCBD–aniline 1, a structural analogue of 2, and F12SubPcCl 6 in toluene (Figures S10.13a and S10.13b, respectively). In stark contrast to what is seen in 2, increasing the temperature from 5 to 65 °C leads to a small decrease of the SubPc localized fluorescence, which is the only emissive state in both SubPcs. A likely rationale infers that fluorescence decreases, in general, with increasing temperature due to higher collision rates with solvent molecules and, in turn, to enhanced fluorescence deactivation via external conversion. (27)

Electrochemical Studies

Next, the redox properties of SubPc–TCBD–aniline conjugates 1 and 2 and their SubPc–ethynyl–aniline precursors 3 and 4 were probed by means of cyclic voltammetry (CV) and square wave voltammetry (SWV). These data are summarized in Table 1. H12SubPc–ethynyl–aniline 3 reveals two one-electron reductions at −1.46 and −2.03 V and three one-electron oxidations at +0.38, +0.46, and +1.00 V (Figure S8.1). While the first oxidation is aniline-centered, all the remaining redox processes are SubPc-centered. Turning to H12SubPc–TCBD–aniline 1, two one-electron reductions at −1.16 and −1.85 V as well as two coalescing one-electron reductions at −1.24 V are observed (Figure S8.2). A comparison of the redox features of 1 with those of TCBD–aniline 7, which presents two TCBD-centered, one-electron reductions at −0.94 and −1.26 V, (12) suggests that the first two reductions are also TCBD-centered in 1. Actually, it is reasonable to assume that the first reduction at −1.16 V is mainly centered on the DCV adjacent to the H12SubPc, whereas the second reduction at −1.24 V is centered on the DCV closer to the aniline. (28) On the other hand, the remaining two electron reductions at −1.24 and −1.85 V are occurring at H12SubPc. It is worth noticing that the H12SubPc-centered reduction at −1.24 V is anodically shifted by 0.22 V with respect to the analogous reduction of precursor 3 due to the strong electron-withdrawing effect exerted by the TCBD moiety in 1. Turning to the oxidative region of 1, two one-electron processes are observed at +0.68 and +0.92 V. While the latter oxidation is assigned as aniline-centered as is the case for the TCBD–aniline in reference 7, which features an oxidation at the same potential, the former oxidation occurs at H12SubPc.
Table 1. Electrochemical Oxidation and Reduction Data (V vs Fc+/Fc) and Electrochemical HOMO–LUMO Gap for Derivatives 1–4 and TCBD–Aniline Reference 7 Detected by SWV at Room Temperature in 0.2 M (for 1–4) and 0.1 M (for 7) Solutions of n-Bu4NPF6 in Dichloromethane
compoundEox3Eox2Eox1Ered1Ered2Ered3Ered4Ered5HOMO–LOMO gap
1 +0.92a+0.68b–1.16c–1.24c–1.24b–1.85b 1.84
2 +0.99b+0.92a–0.84b–1.24c–1.42c–1.88b–2.22b1.76
3+1.00b+0.46b+0.38a–1.46b–2.03b   1.84
4 +0.98b+0.47a–1.04b–1.62b–2.20b  1.51
7 (12)  +0.92a–0.94c–1.26c   1.86
a

Aniline-centered process.

b

SubPc-centered process.

c

TCBD-centered process.

In the next step, the redox features of 2 and its precursor 4 were studied. F12SubPc–ethynyl–aniline 4 undergoes three SubPc-centered, one-electron reductions at −1.04, −1.62, and −2.20 V and two one-electron oxidations at +0.47 and +0.98 V. The latter potentials are attributable to processes involving aniline and the SubPc, respectively (Figure S8.3). Turning to F12SubPc–TCBD–aniline 2, two one-electron oxidations are registered at +0.92 and +0.99 V, which are aniline- and F12SubPc-centered, respectively (Figure S8.4). It is important to note that the latter oxidation occurs in 2 at the same potential as that in its precursor 4; differently to what was observed for 1 (vide supra), the axial, electron-withdrawing TCBD exerts in 2 no profound perturbation of the oxidative features of F12SubPc.
Electrochemical reduction of 2 gives rise to five one-electron reductions at −0.84, −1.24, −1.42, −1.88, and −2.22 V. Hereby, the process at −0.84 V is assigned to the F12SubPc reduction, whereas the second and third reductions are located at the DCVs adjacent to aniline and adjacent to F12SubPc, respectively. Compared to precursor 4, the F12SubPc-centered reduction in 2 is anodically shifted by 0.20 V. A similar shift was observed when comparing the H12SubPc-centered reductions in 1 and 3 (vide supra). This anodic shift is due to directly connecting the electron-accepting TCBD to the SubPc, which renders the macrocycle in 2 more electron-deficient.
Finally, several conclusions should be drawn upon comparing the redox features of 1 and 2. On one hand, an anodic shift of the SubPc-centered oxidation (0.31 V) evolves for 1 versus 2. This shift testifies the higher ionization potential of F12SubPc relative to H12SubPc. On the other hand, a cathodic shift (0.40 V) is observed when comparing the first SubPc-centered reductions of 1 versus 2, which is in sound agreement with the anodic shift (0.42 V) in 3 versus 4 (vide supra). It results from a significantly higher electron affinity of F12SubPc. At this point, it is worth mentioning that the first reduction and oxidation in 1 and 2 occur, however, at different locations. In 1, the first reduction and oxidation are TCBD- and H12SubPc-centered, respectively, whereas in 2, they are F12SubPc- and aniline-centered, respectively. Taking into account that the first reduction and oxidation in 3 and 4 are located at SubPc and aniline, respectively (as in the case of 2), we infer that the different redox behavior of 1 and 2 is a direct consequence of the different electronic effects exerted by the TCBD in the two conjugates, which ultimately depend on the electronic character of the SubPc macrocycle.
The electrochemical HOMO–LUMO band gap for 1–4, which corresponds to the approximate energy level of the radical ion pair states, was then determined as the potential difference between the first oxidation and first reduction (Table 1). For 1–4, values lower than their respective singlet excited-state energies were found, (22) suggesting that, in principle, photoinduced CS can occur for all of these conjugates.

Spectroelectrochemical Studies

As a complement to the absorption, fluorescence, and electrochemical studies, spectroelectrochemical measurements were performed with 3, 6, and 7. This was meant to characterize the spectral features of the one-electron reduced form of F12SubPc, H12SubPc, and TCBD as well as the one-electron oxidized form of aniline. The electrochemical reduction of H12SubPc–ethynyl–aniline 3 at −0.7 V (vs Ag wire) in a toluene/acetonitrile mixture (4:1 v/v) leads to the generation of the H12SubPc•– radical anion, which shows differential absorption features in the form of a distinct minimum at 567 nm as well as maxima at 457, 615, and 677 nm (Figure S9.1). Similarly, electrochemical reduction of F12SubPc–Cl 6 at −0.5 V (vs Ag wire) in ortho-dichlorobenzene results in distinct minima at 535 and 577 nm attributable to the F12SubPc•– radical anion. In addition, a sharp maximum at 500 nm, a shoulder around 470 nm, and three maxima at 615, 675, and 742 nm are discernible (Figure S9.2). Upon electrochemical reduction of 7 at −0.45 V (vs Ag wire) in dichloromethane, an intense minimum at 470 nm together with a shoulder around 432 nm evolves due to the decrease of the characteristic CT band (Figure S9.3a). In parallel, a prominent, broad absorption maximizing around 660 nm and a sharp maximum at 370 nm are observed. On the other hand, electrochemical oxidation of 7 at +1.5 V (vs Ag wire) involves the appearance of a minimum at 478 nm, complemented by a shoulder at 432 nm and a maximum at 370 nm (Figure S9.3b). The spectroelectrochemical features observed upon the reduction and oxidation of 7 correspond to the optical fingerprints of the reduced TCBD and oxidized aniline species, respectively. (12)

Transient Absorption Studies

Details regarding the excited-state deactivation pathways of SubPc–TCBD–aniline conjugates 1 and 2, as well as their precursors 3 and 4, came from transient absorption measurements following femtosecond and nanosecond excitation. H12SubPc–ethynyl–aniline 3 reveals, upon excitation at 550 nm in argon-saturated toluene, differential absorption changes, which include maxima at 433, 612, and 635 nm as well as minima at 525 and 568 nm (Figures S10.14 and S10.15), in addition to a broad differential absorption spanning from 650 to 900 nm. These features relate to the SubPc singlet excited state (2.17 eV), which transforms via intersystem crossing within 1.9 ns into the corresponding triplet excited state with maxima at 460 and 610 nm as well as minima at 525 and 570 nm. Interestingly, a different deactivation mechanism of the SubPc singlet excited state of 3 is observed upon increasing the solvent polarity (Figures S10.16 and S10.17). In this case, the decay of the SubPc singlet excited state, which is formed immediately after the laser pulse, is accompanied by the formation of maxima at 455, 612, and 678 nm as well as minima at 525 and 570 nm in argon-saturated anisole. As a matter of fact, such newly formed transients resemble the spectral changes obtained upon electrochemical reduction of 3 (Figure S9.1). Taking the aforementioned into account, we postulate an electron transfer from aniline to SubPc to afford the metastable H12SubPc•––ethynyl–aniline•+ radical ion pair state (1.84 eV). The underlying charge separation occurs rapidly within 95 ps in chlorobenzene, 73 ps in anisole, and 9.4 ps in benzonitrile, whereas the charge recombination is one-order of magnitude slower with 579 ps in chlorobenzene, 200 ps in anisole, and 56 ps in benzonitrile. A closer look at the differential absorption spectra reveals, on the nanosecond time scale, maxima at 455 and 610 nm and minima at 530 and 570 nm, which attest the formation of the SubPc triplet excited state. The formation of the latter species was also supported by singlet oxygen quantum yield (ΦΔ) experiments. As a matter of fact, a ΦΔ as high as 0.30 is observed in toluene, (29, 30) a value which decreases upon increasing the solvent polarity (i.e., 0.22 in chlorobenzene, 0.12 in anisole, and 0.04 in benzonitrile). This finding can be rationalized considering that, upon increasing the solvent polarity, the H12SubPc•––ethynyl–aniline•+ radical ion pair state becomes more stabilized than the SubPc triplet excited state and, thus, represents the preferred deactivation pathway for the SubPc singlet excited state (Figure S11.3).
Upon 550 nm photoexcitation of F12SubPc–ethynyl–aniline 4 in argon-saturated toluene, transient maxima at 479, 504, 614, 675, and 755 nm as well as transient minima at 535 and 576 nm are discernible attesting the SubPc singlet excited-state formation (Figures S10.18 and S10.19). Next to a slight intensity increase of the 504 and 675 nm maxima, a monoexponential decay of all transients sets in. In light of the electrochemical studies on 4 (vide supra), we infer an intramolecular charge separation. However, a comparison with the literature and the transient features of the F12SubPc•– radical anion in the form of a distinct maximum at 594 nm and a minimum at 517 nm fails to corroborate our hypothesis. (31) As a matter of fact, the instantaneously formed signatures match the spectral features seen upon electrochemical reduction of reference 6 (Figure S9.2). (32) On the basis of these results, we assign the observed transients to a polarized F12SubPcδ−–ethynyl–anilineδ+ CT excited state, in which charge density is redistributed from the aniline to the SubPc, and which deactivates directly into the singlet ground state. Multiwavelength and global analysis yielded ultrafast formation and decay kinetics (4.9/44 ps in toluene, 4.4/15 ps in chlorobenzene, and 4.3/11 ps in anisole). A change in the transient absorption features of 4 is discernible in a more polar solvent such as benzonitrile. In the latter, similar to toluene, transient minima at 535 and 577 nm and maxima at 479, 501, 620, 644, and 755 nm emerge immediately after the conclusion of the laser pulse (Figures S10.20 and S10.21). In contrast to what happens in less polar solvents, these initially formed signatures do not decay; they rather transform into new transients including a sharp maximum at 594 nm as well as a minimum at 517 nm due to the formation of the F12SubPc•– radical anion. (31) The aforementioned result suggests the involvement of the SubPc singlet excited state (2.14 eV) in an intramolecular charge separation affording the formation of a F12SubPc•––ethynyl–aniline•+ radical ion pair state (1.51 eV). In particular, three lifetimes were derived from multiwavelength and global analyses, namely, 1.2, 4.6, and 13 ps. The short-lived component is attributed to the deactivation of the SubPc singlet excited state, giving rise to a polarized CT state. The latter subsequently converts into the fully separated F12SubPc•––ethynyl–aniline•+ radical ion pair state, which finally deactivates to the singlet ground state (Figure S11.4).
In the case of 1, differential absorption changes in the form of transient maxima at 515, 635, and 786 nm evolve immediately after the 550 nm laser excitation in argon-saturated toluene. These are accompanied by a broad absorption reaching into the near-infrared (NIR), as well as transient minima at 439 and 588 nm (Figures S10.22 and S10.23). On one hand, the features at 635 and 786 nm together with the broad absorption extending into the NIR are assigned to the SubPc singlet excited state (2.15 eV) (vide supra). On the other hand, the minima at 439 and 588 nm stem from the bleaching of the ground CT absorption band between SubPc and the axial TCBD (vide supra). Notably, while the broad absorption extending in the NIR decreases, the transient maxima at 515 and 635 nm increase and a new signature maximizing around 660 nm arises with monoexponential kinetics. A comparison with the results obtained from spectroelectrochemistry suggests that the featureless transient around 660 nm and the bleaching are due to the one-electron reduced TCBD (Figure S9.3a). Based on these results, we assume an electron transfer from H12SubPc to TCBD forming a metastable H12SubPc•+–TCBD•––aniline radical ion pair state (1.84 eV). To this end, multiwavelength and global analysis afforded ultrafast charge separation and charge recombination kinetics (7.5/82 ps in toluene, 7.3/24 ps in chlorobenzene, 5.6/23 ps in anisole, and 2.9/16 ps in benzonitrile). At longer times, new transients at 574 and 620 nm are observed, which indicate the formation of the SubPc triplet excited state as a minor deactivation pathway with a ΦΔ of 0.05 in all solvents. It is important to notice that photoexciting 1 at 458 nm, that is mainly into the TCBD–aniline transition, afforded the same kinetics as in the case of the 550 nm photostimulation (Figure S10.24). From this, we infer that, regardless of whether the excitation occurs into the SubPc Q-band or the TCBD–aniline CT band absorptions, the metastable H12SubPc•+–TCBD•––aniline radical ion pair state is populated (Figure S11.2).
When we turn to F12SubPc–TCBD–aniline 2, 550 nm excitation in argon-saturated toluene results in the instantaneous formation of a maximum at 786 nm, a broad absorption reaching into the NIR region, as well as a minimum at 598 nm (Figures 6, S10.26 and S10.27). These fingerprint absorptions, which were also observed in the case of F12SubPc–Cl 6 (Figure S10.25), are assigned to the singlet excited state of F12SubPc (2.05 eV). The decay of these transients is accompanied by the formation of new maxima at 500, 660, and 742 nm and a minimum at 460 nm. Importantly, the underlying dynamics, which are strictly monoexponential, are linked to each other. A spectral comparison with the spectroelectrochemical data suggests that the transients at 500 and 742 nm are attributable to the F12SubPc•– radical anion (Figure S9.2), whereas the broad transient around 660 nm is due to the TCBD•– radical anion (Figure S9.3a). In other words, the negative charge is seemingly delocalized over SubPc and TCBD. Further support for such electronic distribution stems from the bleaching of the ground-state TCBD–aniline CT band absorption at 460 nm, reflecting the TCBD reduction and/or the aniline oxidation (Figure S9.3). Taking the aforementioned data into account, we postulate the formation of an [(F12SubPc–TCBD)δ−–anilineδ+]* exciplex species, in which redistribution of charge density characterizes the excited state.

Figure 6

Figure 6. Evolution associated spectra and associated time-dependent amplitudes (inset) obtained upon femtosecond flash photolysis (550 nm, 150 nJ) of F12SubPc–TCBD–aniline conjugate 2 (2 × 10–5 M) in argon-saturated toluene monitoring the exciplex formation and decay processes.

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Multiwavelength and global analysis yielded formation and decay kinetics of 3.5/1300 ps in toluene, 4.7/648 ps in chlorobenzene, and 4.3/505 ps in anisole. Interestingly, these values are quite close to those obtained by time-resolved fluorescence measurements (λem = 650 nm) with 1.3 ns in toluene, 0.6 ns in chlorobenzene, and 0.5 ns in anisole (Figure S10.28). Our findings support the radiative exciplex deactivation hypothesis. On the other hand, the lack of any radiative exciplex feature of 2 in benzonitrile (vide supra) leads us to hypothesize that, in this solvent, the (F12SubPc–TCBD)•––aniline•+ radical ion pair state (1.76 eV) is formed with charge separation and charge recombination kinetics of 3.5 and 61 ps, respectively. At the end of the femtosecond experiments, maxima at 443, 488, and 660 nm and minima at 467, 535, and 598 nm are still observed. Complementary nanosecond experiments confirm that the origin of such long-lived transients is the SubPc triplet excited state, with ΦΔ decreasing upon increasing the solvent polarity (0.18 in toluene, 0.14 in chlorobenzene, 0.11 in anisole, and 0.00 in benzonitrile). In other words, two different scenarios take place depending on the polarity of the medium. In low polar solvents, the SubPc singlet excited state deactivates forming the exciplex species, which eventually decays to the ground state through an energetically lower-lying SubPc triplet excited state (Figure 7a).

Figure 7

Figure 7. Energy level diagrams of F12SubPc–TCBD–aniline conjugate 2 reflecting the energetic pathways in (a) toluene and (b) benzonitrile after excitation of the F12SubPc (λex = 550 nm, green arrow) and TCBD–aniline band (λex = 458 nm, blue arrow). Red wavy arrow refers to fluorescence emission, whereas black lines refer to nonradiative processes.

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Conversely, in high polar solvents, the SubPc singlet excited state mainly deactivates by populating the radical ion pair state, which lies energetically below that of the exciplex and the SubPc triplet excited state and transforms directly into the singlet ground state (Figure 7b). Worthy of mention is that the same kinetics are also observed upon 458 nm excitation in the four investigated solvents, which indicates that the formation of the exciplex and/or radical ion pair state also proceeds upon excitation of the TCBD–aniline ground-state CT band (Figure S10.30).

Conclusions

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In this work, we have reported two novel D–A conjugates, in which an electroactive TCBD–aniline has been connected, for the first time, at the axial position of either electron-donating H12SubPc or electron-accepting F12SubPc. In-depth structural, electrochemical, as well as photophysical characterization of both SubPc–TCBD–aniline derivatives, synthesized in excellent yields by CA–RE reaction of alkynyl-functionalized SubPcs with tetracyanoethylene, provided several interesting features never observed before in any SubPc- or TCBD-based derivative.
While both conjugates were fully characterized by a wide range of spectroscopic and spectrometric techniques, decisive information about their structural features was obtained by X-ray analysis. To this end, H12SubPc–TCBD–aniline and F12SubPc–TCBD–aniline crystallize in a dimeric and columnar packing arrangement, respectively. They are racemic mixtures of two atropisomers resulting from the nonplanar geometry adopted by the axial TCBD. Both atropisomers of each SubPc–TCBD–aniline conjugate were separated by chiral HPLC. Although several TCBD-based systems have been reported to date, only one of them, which is based on TCBD directly attached to a methyl-substituted C60 fullerene, has been separated into its constitutive atropisomers. (18) In our case, single crystals suitable for X-ray analysis were grown out of enantiopure samples of H12SubPc–TCBD–aniline and F12SubPc–TCBD–aniline allowing us to unequivocally assign, for the first time, the absolute configuration of TCBD-based atropisomers.
Besides their interesting structural features, SubPc–TCBD–aniline conjugates exhibit unique photophysical properties. On one hand, H12SubPc–TCBD–aniline presents ground-state CT interactions between H12SubPc and the axial TCBD, something never observed before in SubPc chemistry. Ground-state CT interactions have been postulated to mediate the charge separation in D–A blends of organic materials in terms of a real state, which assists in charge separation and recombination with a beneficial effect in photovoltaic performances. (33) On the other hand, F12SubPc–TCBD–aniline gave rise to an intense and broad emission extending into the NIR region due to the formation of an intramolecular exciplex. Such exciplex emission stems from a polarized CT state, which is a direct result of the geometry adopted by the F12SubPc–TCBD–aniline allowing for intramolecular interactions in the excited state between the spatially close electron-rich aniline and F12SubPc. The formation of an exciplex, which was corroborated by time-dependent absorption and fluorescence studies, is, to the best of our knowledge, a finding completely peerless in the context of SubPc- and TCBD-based chemistry. Finally, for both SubPc–TCBD–aniline derivatives, complementary transient absorption studies demonstrated the occurrence of photoinduced charge separation processes, which, together with the aforementioned ground- and excited-state features, render these systems promising materials for applications in the field of molecular photovoltaics.

Supporting Information

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The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/jacs.7b01460.

  • Details of the synthesis of compounds 1–7 and their electrochemical and photophysical characterization, chiral HPLC profiles, CD data, and X-ray structure of racemates 1 and 2 and atropisomers Sa-1 and Ra-2 (PDF)

  • X-ray data of Sa-1 (CIF)

  • X-ray data of 1 (CIF)

  • X-ray data of Ra-2 (CIF)

  • X-ray data of 2 (CIF)

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Author Information

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  • Corresponding Authors
    • Dirk M. Guldi - Department of Chemistry and Pharmacy, Interdisciplinary Center for Molecular Materials (ICMM), Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen, Germany;  Orcidhttp://orcid.org/0000-0002-3960-1765;  Email: [email protected]
    • Tomás Torres - Departamento de Química Orgánica, Universidad Autónoma de Madrid, 28049 Madrid, Spain;  IMDEA-Nanociencia, Campus de Cantoblanco, 28049 Madrid, Spain;  Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, 28049 Madrid, Spain;  Email: [email protected]
    • Giovanni Bottari - Departamento de Química Orgánica, Universidad Autónoma de Madrid, 28049 Madrid, Spain;  IMDEA-Nanociencia, Campus de Cantoblanco, 28049 Madrid, Spain;  Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, 28049 Madrid, Spain;  Orcidhttp://orcid.org/0000-0001-6141-7027;  Email: [email protected]
  • Authors
    • Kim A. Winterfeld - Department of Chemistry and Pharmacy, Interdisciplinary Center for Molecular Materials (ICMM), Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen, Germany
    • Giulia Lavarda - Departamento de Química Orgánica, Universidad Autónoma de Madrid, 28049 Madrid, Spain
    • Julia Guilleme - Departamento de Química Orgánica, Universidad Autónoma de Madrid, 28049 Madrid, Spain
    • Michael Sekita - Department of Chemistry and Pharmacy, Interdisciplinary Center for Molecular Materials (ICMM), Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen, Germany
  • Notes
    The authors declare no competing financial interest.

Acknowledgment

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Financial support from Solar Technologies Go Hybrid (Sol-Tech), SFB953, Comunidad de Madrid, Spain (S2013/MIT-2841, FOTOCARBON), and Spanish MICINN (CTQ2014-52869-P) is acknowledged.

References

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This article references 33 other publications.

  1. 1
    Molecular Mechanisms of Photosynthesis; Blankenship, R. E., Ed.; Blackwell Science: Oxford, UK, 2002.
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  2. 2
    (a) Special Issue on Artificial Photosynthesis and Solar Fuels. Acc. Chem. Res. 2009, 42, 1859– 2029.
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
    (b) Mishra, A.; Bäuerle, P. Angew. Chem., Int. Ed. 2012, 51, 2020– 2067 DOI: 10.1002/anie.201102326
    [Crossref], [CAS], Google Scholar
    2b
    Small Molecule Organic Semiconductors on the Move: Promises for Future Solar Energy Technology
    Mishra, Amaresh; Baeuerle, Peter
    Angewandte Chemie, International Edition (2012), 51 (9), 2020-2067CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A review. This article, written from an org. chemist's point of view, provides an up-to-date overview of org. solar cells based on small mols. or oligomers as absorbers and describes devices that incorporate planar-heterojunctions and bulk heterojunctions between a donor (p-type semiconductor) and an acceptor (n-type semiconductor) material. The article pays particular attention to the design and development of mol. materials and their performance in corresponding devices. In recent years, a substantial amt. of both, academic and industrial research, has been directed towards org. solar cells, in an effort to develop new materials and to improve their tunability, processability, power conversion efficiency, and stability. On the eve of commercialization of org. solar cells, this review provides an overview of efficiencies attained with small mols./oligomers in org. solar cells and summarizes materials and device concepts developed over the last decade. Approaches to enhancing the efficiency of org. solar cells are analyzed.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xitlygs7g%253D&md5=3bd032ed84f6c2a11c7f6d8efb770901
    (c) Fukuzumi, S.; Ohkubo, K.; Suenobu, T. Acc. Chem. Res. 2014, 47, 1455– 1464 DOI: 10.1021/ar400200u
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    2c
    Long-Lived Charge Separation and Applications in Artificial Photosynthesis
    Fukuzumi, Shunichi; Ohkubo, Kei; Suenobu, Tomoyoshi
    Accounts of Chemical Research (2014), 47 (5), 1455-1464CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
    A review. Researchers have long been interested in replicating the reactivity that occurs in photosynthetic organisms. To mimic the long-lived charge sepns. characteristic of the reaction center in photosynthesis, researchers have applied the Marcus theory to design synthetic multistep electron-transfer (ET) systems. In this Account, the authors describe their recent research on the rational design of ET control systems, based on models of the photosynthetic reaction center that rely on the Marcus theory of ET. The key to obtaining a long-lived charge sepn. is the careful choice of electron donors and acceptors that have small reorganization energies of ET. In these cases, the driving force of back ET is located in the Marcus inverted region, where the lifetime of the charge-sepd. state lengthens as the driving force of back ET increases. The authors chose porphyrins as electron donors and fullerenes as electron acceptors, both of which have small ET reorganization energies. By linking electron donor porphyrins and electron acceptor fullerenes at appropriate distances, we achieved charge-sepd. states with long lifetimes. The authors could further lengthen the lifetimes of charge-sepd. states by mixing a variety of components, such as a terminal electron donor, an electron mediator, and an electron acceptor, mimicking both the photosynthetic reaction center and the multistep photoinduced ET that occurs there. However, each step in multistep ET loses a fraction of the initial excitation energy during the long-distance charge sepn. To overcome this drawback in multistep ET systems, the authors used designed new systems where we could finely control the redox potentials and the geometry of simple donor-acceptor dyads. These modifications resulted in a small ET reorganization energy and a high-lying triplet excited state. The authors most successful example, 9-mesityl-10-methylacridinium ion (Acr+-Mes), can undergo a fast photoinduced ET from the mesityl (Mes) moiety to the singlet excited state of the acridinium ion moiety (Acr+) with extremely slow back ET. The high-energy triplet charge-sepd. state is located deep in the Marcus inverted region, and the authors have detected the structural changes during the photoinduced ET in this system using x-ray crystallog. To increase the efficiency of both the light-harvesting and photoinduced ET, the authors assembled the Acr+-Mes dyads on gold nanoparticles to bring them in closer proximity to one another. The authors can also incorporate Acr+-Mes mols. within nanosized mesoporous silica-alumina. In contrast to the densely assembled dyads on gold nanoparticles, each Acr+-Mes mol. in silica-alumina is isolated in the mesopore, which inhibits the bimol. back ET and leads to longer lifetimes in soln. at room temp. than the natural photosynthetic reaction center. Acr+-Mes and related compds. act as excellent org. photocatalysts and facilitate a variety of reactions such as oxygenation, bromination, carbon-carbon bond formation, and hydrogen evolution reactions.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXntlKnsb8%253D&md5=483d15654c5ed67b268b97396d092527
    (d) Hammarström, L. Acc. Chem. Res. 2015, 48, 840– 850 DOI: 10.1021/ar500386x
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    2d
    Accumulative charge separation for solar fuels production: coupling light-induced single electron transfer to multielectron catalysis
    Hammarstrom Leif
    Accounts of chemical research (2015), 48 (3), 840-50 ISSN:.
    The conversion and storage of solar energy into a fuel holds promise to provide a significant part of the future renewable energy demand of our societies. Solar energy technologies today generate heat or electricity, while the large majority of our energy is used in the form of fuels. Direct conversion of solar energy to a fuel would satisfy our needs for storable energy on a large scale. Solar fuels can be generated by absorbing light and converting its energy to chemical energy by electron transfer leading to separation of electrons and holes. The electrons are used in the catalytic reduction of a cheap substrate with low energy content into a high-energy fuel. The holes are filled by oxidation of water, which is the only electron source available for large scale solar fuel production. Absorption of a single photon typically leads to separation of a single electron-hole pair. In contrast, fuel production and water oxidation are multielectron, multiproton reactions. Therefore, a system for direct solar fuel production must be able to accumulate the electrons and holes provided by the sequential absorption of several photons in order to complete the catalytic reactions. In this Account, the process is termed accumulative charge separation. This is considerably more complicated than charge separation on a single electron level and needs particular attention. Semiconductor materials and molecular dyes have for a long time been optimized for use in photovoltaic devices. Efforts are made to develop new systems for light harvesting and charge separation that are better optimized for solar fuel production than those used in the early devices presented so far. Significant progress has recently been made in the discovery and design of better homogeneous and heterogeneous catalysts for solar fuels and water oxidation. While the heterogeneous ones perform better today, molecular catalysts based on transition metal complexes offer much greater tunability of electronic and structural properties, they are typically more amenable to mechanistic analysis, and they are small and therefore require less material. Therefore, they have arguably greater potential as future efficient catalysts but must be efficiently coupled to accumulative charge separation. This Account discusses accumulative charge separation with focus on molecular and molecule-semiconductor hybrid systems. The coupling between charge separation and catalysis involves many challenges that are often overlooked, and they are not always apparent when studying water oxidation and fuel formation as separate half-reactions with sacrificial agents. Transition metal catalysts, as well as other multielectron donors and acceptors, cycle through many different states that may quench the excited sensitizer by nonproductive pathways. Examples where this has been shown, often with ultrafast rates, are reviewed. Strategies to avoid these competing energy-loss reactions and still obtain efficient coupling of charge separation to catalysis are discussed. This includes recent examples of dye-sensitized semiconductor devices with molecular catalysts and dyes that realize complete water splitting, albeit with limited efficiency.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC2MrkslGqsw%253D%253D&md5=653b29826f7380d895c143a83c96a684
  3. 3
    (a) Claessens, C. G.; Gonzalez-Rodríguez, D.; Torres, T. Chem. Rev. 2002, 102, 835– 853 DOI: 10.1021/cr0101454
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
    (b) Claessens, C. G.; Gonzalez-Rodríguez, D.; Rodríguez-Morgade, M. S.; Medina, A.; Torres, T. Chem. Rev. 2014, 114, 2192– 2277 DOI: 10.1021/cr400088w
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  4. 4
    (a) Gonzalez-Rodríguez, D.; Torres, T.; Guldi, D. M.; Rivera, J.; Herranz, M. A.; Echegoyen, L. J. Am. Chem. Soc. 2004, 126, 6301– 6313 DOI: 10.1021/ja039883v
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
    (b) El-Khouly, M. E.; Shim, S. H.; Araki, Y.; Ito, O.; Kay, K.-Y. J. Phys. Chem. B 2008, 112, 3910– 3917 DOI: 10.1021/jp7108658
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
    (c) Gonzalez-Rodríguez, D.; Carbonell, E.; Guldi, D. M.; Torres, T. Angew. Chem., Int. Ed. 2009, 48, 8032– 8036 DOI: 10.1002/anie.200902767
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
    (d) Sanchez-Molina, I.; Claessens, C. G.; Grimm, B.; Guldi, D. M.; Torres, T. Chem. Sci. 2013, 4, 1338– 1344 DOI: 10.1039/c3sc21956a
    [Crossref], [CAS], Google Scholar
    4d
    Trapping fullerenes with jellyfish-like subphthalocyanines
    Sanchez-Molina, I.; Claessens, C. G.; Grimm, B.; Guldi, D. M.; Torres, T.
    Chemical Science (2013), 4 (3), 1338-1344CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
    Six electronically different concave-shaped subphthalocyanines (SubPcs) were prepd. for testing the structural factors governing fullerenes encapsulation. Thus, the supramol. interaction of SubPcs with C60 and C70 fullerenes in soln. was studied by Job's plot and titrn. expts., which yielded quant. information on both the stoichiometry and strength of the complexes in toluene soln. The importance of the electronic nature of the SubPc was demonstrated, as it influences not only the stability of the complex, but also its stoichiometry. Alkyl chains incorporated in hexaalkylthio-substituted SubPcs seem to in some way cooperate in the binding process and influence its kinetics. In the resulting 2:1 complexes, the large absorption cross section of SubPcs throughout the visible part of the spectrum is the beginning of an unidirectional energy transfer to funnel the excited state energy from the periphery (i.e., two SubPcs) to the core (i.e., C60 and C70).
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    (e) Sanchez-Molina, I.; Grimm, B.; Krick Calderon, R. M.; Claessens, C. G.; Guldi, D. M.; Torres, T. J. Am. Chem. Soc. 2013, 135, 10503– 10511 DOI: 10.1021/ja404234n
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  5. 5
    (a) González-Rodríguez, D.; Torres, T.; Olmstead, M. M.; Rivera, J.; Herranz, M. A.; Echegoyen, L.; Atienza-Castellanos, C.; Guldi, D. M. J. Am. Chem. Soc. 2006, 128, 10680– 10681 DOI: 10.1021/ja0632409
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
    (b) Maligaspe, E.; Hauwiller, M. R.; Zatsikha, Y. V.; Hinke, J. A.; Solntsev, P. V.; Blank, D. A.; Nemykin, V. N. Inorg. Chem. 2014, 53, 9336– 9347 DOI: 10.1021/ic5014544
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
    (c) El-Khouly, M. E.; El-Kemary, M. A.; El-Refaey, A.; Kay, K.-Y.; Fukuzumi, S. J. Porphyrins Phthalocyanines 2016, 20, 1148– 1155 DOI: 10.1142/S1088424616500784
    [Crossref], [CAS], Google Scholar
    5c
    Light harvesting subphthalocyanine-ferrocene dyads: Fast electron transfer process studied by femtosecond laser photolysis
    El-Khouly, Mohamed E.; El-Kemary, Maged A.; El-Refaey, Ahmed; Kay, Kwang-Yol; Fukuzumi, Shunichi
    Journal of Porphyrins and Phthalocyanines (2016), 20 (8/11), 1148-1155CODEN: JPPHFZ; ISSN:1088-4246. (World Scientific Publishing Co. Pte. Ltd.)
    Ferrocene-subphthalocyanine dyads characterized, where ferrocene is axially linked with subphthalocyanine at its axial position with the B-O bond through the para and metapositions, namely Fc-pPhO-SubPc (dyad 1) and Fc-mPhO-SubPc (dyad 2). The geometric and electronic structures of 1 and 2 were probed by ab initio B3LYP/6-311G methods. The optimized structures showed that the Fc and SubPc entities are sepd. by 8.42 and 7.40 Å for dyads 1 and 2, resp. The distribution of the highest occupied frontier MO (HOMO) was found to be located on the Fc entity, while the LUMO (LUMO) was located on the SubPc entity, suggesting that the charge-sepd. states of the are Fc+-SubPc-. Upon photoexcitation at the subphthalocyanine unit, both dyads undergo photoinduced electron transfer to form the corresponding charge-sepd. species, Fc+-SubPc-. Based on their redox potentials detd. by cyclic voltammetry technique, the direction of the charge sepn. and the energies of these states have been revealed. Femtosecond transient spectroscopic studies have revealed that a fast charge sepn. of 8.8 × 1010 and 1.2 × 1011 s-1 for 1 and 2, resp., indicating fast charge sepn. in these simple dyads.
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  6. 6
    (a) Xu, H.; Ng, D. K. P. Inorg. Chem. 2008, 47, 7921– 7927 DOI: 10.1021/ic800756h
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
    (b) El-Khouly, M. E.; Ryu, J. B.; Kay, K.-Y.; Ito, O.; Fukuzumi, S. J. Phys. Chem. C 2009, 113, 15444– 15453 DOI: 10.1021/jp904310f
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
    (c) El-Khouly, M. E.; Ju, D. K.; Kay, K.-Y.; D’Souza, F.; Fukuzumi, S. Chem. - Eur. J. 2010, 16, 6193– 6202 DOI: 10.1002/chem.201000045
    [Crossref], [PubMed], [CAS], Google Scholar
    6c
    Supramolecular Tetrad of Subphthalocyanine-Triphenylamine-Zinc Porphyrin Coordinated to Fullerene as an "Antenna-Reaction-Center" Mimic: Formation of a Long-Lived Charge-Separated State in Nonpolar Solvent
    El-Khouly, Mohamed E.; Ju, Dong Kyu; Kay, Kwang-Yol; D'Souza, Francis; Fukuzumi, Shunichi
    Chemistry - A European Journal (2010), 16 (21), 6193-6202, S6193/1-S6193/6CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The authors report formation of a long-lived charge-sepd. state of a self-assembled donor-acceptor tetrad, formed by axial coordination of a fulleropyrrolidine appended with an imidazole coordinating ligand (C60Im) to the Zn center of a subphthalocyanine-triphenylamine-zinc porphyrin (SubPc-TPA-ZnP), as a charge-stabilizing antenna reaction center mimic in toluene. The subphthalocyanine and triphenylamine entities, with their high-energy singlet states, act as an energy-transferring antenna unit to produce a singlet Zn porphyrin. The formation const. for the self-assembled tetrad was detd. to be 1.0×104 M-1, suggesting a moderately stable complex formation. The geometric and electronic structures of the covalently linked SubPc-TPA-ZnP triad and self-assembled SubPc-TPA-ZnP:C60Im tetrad were examd. by using an ab initio B3LYP/6-31G method. The majority of the highest occupied frontier MO was found over the ZnP and TPA entities, whereas the LUMO was located over the fullerene entity, suggesting the formation of the radical-ion pair (SubPc-TPA-ZnP·+:C60Im·-). The redox measurements revealed that the energy level of the radical-ion pair in toluene is located lower than that of the singlet and triplet states of the zinc porphyrin and fullerene entities. The femtosecond transient absorption measurements revealed fast charge sepn. from the singlet porphyrin to the coordinated C60Im with a lifetime of 1.1 ns. Interestingly, slow charge recombination (1.6 × 105 s-1) and the long lifetime of the charge-sepd. state (6.6 μs) were obtained in toluene by utilizing the nanosecond transient measurements.
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    (d) Menting, R.; Lau, J. T. F.; Xu, H.; Ng, D. K. P.; Röder, B.; Ermilov, E. A. Chem. Commun. 2012, 48, 4597– 4599 DOI: 10.1039/c2cc30286a
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
    (e) Managa, M.; Mack, J.; Gonzalez-Lucasb, D.; Remiro-Buenamañana, S.; Tshangana, C.; Cammidge, A. N.; Nyokong, T. J. Porphyrins Phthalocyanines 2016, 20, 1– 20 DOI: 10.1142/S1088424615500959
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  7. 7
    (a) González-Rodríguez, D.; Claessens, C. G.; Torres, T.; Liu, S.-G.; Echegoyen, L.; Vila, N.; Nonell, S. Chem. - Eur. J. 2005, 11, 3881– 3893 DOI: 10.1002/chem.200400779
    [Crossref], [PubMed], [CAS], Google Scholar
    7a
    Tuning photoinduced energy- and electron-transfer events in subphthalocyanine-phthalocyanine dyads
    Gonzalez-Rodriguez, David; Claessens, Christian G.; Torres, Tomas; Liu, Shenggao; Echegoyen, Luis; Vila, Nuria; Nonell, Santi
    Chemistry - A European Journal (2005), 11 (13), 3881-3893CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A series of subphthalocyanine-phthalocyanine dyads has been prepd. by palladium-catalyzed cross-coupling reactions between a monoalkynylphthalocyanine and different monoiodosubphthalocyanines. Electronic coupling between the two photoactive units is ensured by a rigid and π-conjugated alkynyl spacer. In addn., the electronic characteristics of the subphthalocyanine moiety were modulated by the introduction of different peripheral substituents. Cyclic and Osteryoung square-wave voltammetry expts. revealed that the redn. potential of this subunit can be decreased by about 400 mV on going from thioether or no substituents to nitro groups. As a consequence, the energy level of the charge-transfer state could be fine-tuned so as to gain control over the fate of the photoexcitation energy in each subunit. The diverse steady-state and time-resolved photophys. techniques employed demonstrated that, when the charge-transfer state lies high in energy, a quant. singlet-singlet energy-transfer mechanism from the excited subphthalocyanine to the phthalocyanine takes place. On the contrary, stabilization of the radical pair by lowering the redox gap between electron donor and acceptor results in a highly efficient photoinduced electron-transfer process, even in solvents of low polarity such as toluene (ΦET ≈ 0.9). These features, together with the extraordinary absorptive cross section that these mol. ensembles display across the whole UV/Vis spectrum, make them model candidates for application in situations where broadband light sources are needed.
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    (b) Zhao, Z.; Cammidge, A. N.; Cook, M. J. Chem. Commun. 2009, 7530– 7532 DOI: 10.1039/b916649a
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  8. 8
    (a) Cnops, K.; Rand, B. P.; Cheyns, D.; Verreet, B.; Empl, M. A.; Heremans, P. Nat. Commun. 2014, 5, 3406 DOI: 10.1038/ncomms4406
    [Crossref], [PubMed], [CAS], Google Scholar
    8a
    8.4% efficient fullerene-free organic solar cells exploiting long-range exciton energy transfer
    Cnops Kjell; Empl Max A; Heremans Paul; Rand Barry P; Cheyns David; Verreet Bregt
    Nature communications (2014), 5 (), 3406 ISSN:.
    In order to increase the power conversion efficiency of organic solar cells, their absorption spectrum should be broadened while maintaining efficient exciton harvesting. This requires the use of multiple complementary absorbers, usually incorporated in tandem cells or in cascaded exciton-dissociating heterojunctions. Here we present a simple three-layer architecture comprising two non-fullerene acceptors and a donor, in which an energy-relay cascade enables an efficient two-step exciton dissociation process. Excitons generated in the remote wide-bandgap acceptor are transferred by long-range Forster energy transfer to the smaller-bandgap acceptor, and subsequently dissociate at the donor interface. The photocurrent originates from all three complementary absorbing materials, resulting in a quantum efficiency above 75% between 400 and 720 nm. With an open-circuit voltage close to 1 V, this leads to a remarkable power conversion efficiency of 8.4%. These results confirm that multilayer cascade structures are a promising alternative to conventional donor-fullerene organic solar cells.
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    (b) Duan, C.; Zango, G.; García Iglesias, M.; Colberts, F. J. M.; Wienk, M. M.; Martínez-Díaz, M. V.; Janssen, R. A. J.; Torres, T. Angew. Chem., Int. Ed. 2017, 56, 148– 152 DOI: 10.1002/anie.201608644
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  9. 9
    Michinobu, T.; Boudon, C.; Gisselbrecht, J.-P.; Seiler, P.; Frank, B.; Moonen, N. N. P.; Gross, M.; Diederich, F. Chem. - Eur. J. 2006, 12, 1889– 1905 DOI: 10.1002/chem.200501113
    [Crossref], [PubMed], [CAS], Google Scholar
    9
    Donor-substituted 1,1,4,4-Tetracyanobutadienes (TCBDs). New chromophores with efficient intramolecular charge-transfer interactions by atom-economic synthesis
    Michinobu, Tsuyoshi; Boudon, Corinne; Gisselbrecht, Jean-Paul; Seiler, Paul; Frank, Brian; Moonen, Nicolle N. P.; Gross, Maurice; Diederich, Francois
    Chemistry - A European Journal (2006), 12 (7), 1889-1905CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A wide variety of monomeric and oligomeric, donor-substituted 1,1,4,4-tetracyanobutadienes (TCBDs) have been synthesized by [2+2] cycloaddn. between tetracyanoethylene (TNCE) and donor-substituted alkynes, followed by electrocyclic ring opening of the initially formed cyclobutenes. Reaction yields are often nearly quant. but can be affected by the electron-donating power and steric demands of the alkyne substituents. The intramol. charge-transfer (CT) interactions between the donor and TCBD acceptor moieties were comprehensively investigated by X-ray crystallog., electrochem., UV-visible spectroscopy, and theor. calcns. Despite the nonplanarity of the new chromophores, which have a substantial twist between the two dicyanovinyl planes, efficient intramol. CT interactions are obsd., and the crystal structures demonstrate a high quinoid character in strong donor substituents, such as N,N-dimethylanilino (DMA) rings. The maxima of the CT bands shift bathochromically upon redn. of the amt. of conjugative coupling between strong donor and acceptor moieties. Each TCBD moiety undergoes two reversible, one-electron redn. steps. Thus, a tri-TCBD deriv. with a 1,3,5-trisubstituted benzene core shows six reversible redn. steps within an exceptionally narrow potential range of 1.0 V. The first redn. potential Ered,1 is strongly influenced by the donor substitution: introduction of more donor moieties causes an increasingly twisted TCBD structure, a fact that results in the elevation of the LUMO level and, consequently, a more difficult first redn. The potentials are also strongly influenced by the nature of the donor residues and the extent of donor-acceptor coupling. A careful comparison of electrochem. data and the correlation with UV-visible spectra made it possible to est. unknown phys. parameters such as the Ered,1 of unsubstituted TCBD (-0.31 V vs. Fc+/Fc) as well as the maxima of highly broadened CT bands. Donor-substituted TCBDs are stable mols. and can be sublimed without decompn. With their high third-order optical non-linearities, as revealed in preliminary measurements, they should become interesting chromophores for ultra-thin film formation by vapor deposition techniques and have applications in opto-electronic devices.
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  10. 10
    (a) Tancini, F.; Monti, F.; Howes, K.; Belbakra, A.; Listorti, A.; Schweizer, W. B.; Reutenauer, P.; Alonso-Gómez, J.-L.; Chiorboli, C.; Urner, L. M.; Gisselbrecht, J.-P.; Boudon, C.; Armaroli, N.; Diederich, F. Chem. - Eur. J. 2014, 20, 202– 216 DOI: 10.1002/chem.201303284
    [Crossref], [PubMed], [CAS], Google Scholar
    10a
    Cyanobuta-1,3-dienes as novel electron acceptors for photoactive multicomponent systems
    Tancini, Francesca; Monti, Filippo; Howes, Kara; Belbakra, Abdelhalim; Listorti, Andrea; Schweizer, W. Bernd; Reutenauer, Philippe; Alonso-Gomez, Jose-Lorenzo; Chiorboli, Claudio; Urner, Lorenz M.; Gisselbrecht, Jean-Paul; Boudon, Corinne; Armaroli, Nicola; Diederich, Francois
    Chemistry - A European Journal (2014), 20 (1), 202-216CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The synthesis, electrochem., and photophys. properties of five multicomponent systems featuring a ZnII porphyrin (ZnP) linked to one or two anilino donor-substituted pentacyano- (PCBD) or tetracyanobuta-1,3-dienes (TCBD), with and without an interchromophoric bridging spacer (S), are reported: ZnP-S-PCBD (1), ZnP-S-TCBD (2), ZnP-TCBD (3), ZnP-(S-PCBD)2 (4), and ZnP-(S-TCBD)2 (5). By means of steady-state and time-resolved absorption and luminescence spectroscopy (RT and 77 K), photoinduced intramol. energy and electron transfer processes are evidenced, upon excitation of the porphyrin unit. In systems equipped with the strongest acceptor PCBD and the spacer (1, 4), no evidence of electron transfer is found in toluene, suggesting ZnP→PCBD energy transfer, followed by ultrafast (<10 ps) intrinsic deactivation of the PCBD moiety. In the analogous systems with the weaker acceptor TCBD (2, 5), photoinduced electron transfer occurs in benzonitrile, generating a charge-sepd. (CS) state lasting 2.3 μs. Such a long lifetime, in light of the high Gibbs free energy for charge recombination (ΔGCR=-1.39 eV), suggests a back-electron transfer process occurring in the so-called Marcus inverted region. Notably, in system 3 lacking the interchromophoric spacer, photoinduced charge sepn. followed by charge recombination occur within 20 ps. This is a consequence of the close vicinity of the donor-acceptor partners and of a virtually activationless electron transfer process. These results indicate that the strongly electron-accepting cyanobuta-1,3-dienes might become promising alternatives to quinone-, perylenediimide-, and fullerene-derived acceptors in multicomponent modules featuring photoinduced electron transfer.
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    (b) Koszelewski, D.; Nowak-Król, A.; Gryko, D. T. Chem. - Asian J. 2012, 7, 1887– 1894 DOI: 10.1002/asia.201200179
    [Crossref], [PubMed], [CAS], Google Scholar
    10b
    Selective Cycloaddition of Tetracyanoethene (TCNE) and 7,7,8,8-Tetracyano-p-quinodimethane (TCNQ) to Afford meso-Substituted Phenylethynyl Porphyrins
    Koszelewski, Dominik; Nowak-Krol, Agnieszka; Gryko, Daniel T.
    Chemistry - An Asian Journal (2012), 7 (8), 1887-1894, S1887/1-S1887/24CODEN: CAAJBI; ISSN:1861-4728. (Wiley-VCH Verlag GmbH & Co. KGaA)
    π-Extended TCBD-porphyrins that contains a 1,1,4,4-tetracyanobuta-1,3-diene unit were prepd. by a highly efficient [2+2] cycloaddn. of tetracyanoethene (TCNE) or 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) with meso-substituted trans-A2B2-porphyrins contg. two arylethynyl groups, followed by a retro-electrocyclization reaction. Depending on the electronic properties of the arylethynyl groups, the cycloaddn. reaction took place exclusively on either one or two ethynyl moieties with high yields. The addn. of TCNQ proceeded with complete regioselectivity. The resulting π-expanded TCBD-porphyrins had a hypsochromically shifted Soret band and showed unique, broad absorption in the visible region.
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  11. 11
    Wu, Y.-L.; Stuparu, M. C.; Boudon, C.; Gisselbrecht, J.-P.; Schweizer, W. B.; Baldridge, K. K.; Siegel, J. S.; Diederich, F. J. Org. Chem. 2012, 77, 11014– 11026 DOI: 10.1021/jo302217n
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    11
    Structural, Optical, and Electrochemical Properties of Three-Dimensional Push-Pull Corannulenes
    Wu, Yi-Lin; Stuparu, Mihaiela C.; Boudon, Corinne; Gisselbrecht, Jean-Paul; Schweizer, W. Bernd; Baldridge, Kim K.; Siegel, Jay S.; Diederich, Francois
    Journal of Organic Chemistry (2012), 77 (24), 11014-11026CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)
    Electrochem. active corannulene derivs. with various nos. of electron-donating 4-(N,N-dimethylamino)phenylethynyl (1-4) or electron-withdrawing cyanobutadienyl peripheral substituents (5-8) were prepd. The latter derivs. resulted from formal [2 + 2] cycloaddn. of cyanoolefins to 1-4 followed by retro-electrocyclization. Conformational properties were examd. by variable-temp. NMR and X-ray diffraction and opto-electronic properties by electronic absorption/emission spectra and electrochem. measurements; these analyses were corroborated by dispersion-cor. d. functional calcns. at the level of B97-D/def2-TZVPP. In CH2Cl2, 1-4 exhibit intramol. charge-transfer (ICT) absorptions at 350-550 nm and green (λem ∼ 540 nm) or orange (600 nm) fluorescence with high quantum yields (56-98%) and are more readily reduced than corannulene by up to 490 mV. The variation of optical gap and redox potentials of 1-4 does not correlate with the no. of substituents. Cyanobutadienyl corannulenes 5-8 show red-shifted ICT absorptions with end-absorptions approaching 800 nm. Intersubstituent interactions lead to distortions of the corannulene core and lower the mol. symmetry. NMR, X-ray, and computational studies on 5 and 8 with one cyanobutadienyl substituent suggested the formation of intermol. corannulene dimers. Bowl-inversion barriers around ΔG‡ = 10-11 kcal/mol were detd. for these two mols.
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  12. 12
    Sekita, M.; Ballesteros, B.; Diederich, F.; Guldi, D. M.; Bottari, G.; Torres, T. Angew. Chem., Int. Ed. 2016, 55, 5560– 5564 DOI: 10.1002/anie.201601258
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  13. 13

    See section 4 in the Supporting Information.

    There is no corresponding record for this reference.
  14. 14
    Camerel, F.; Ulrich, G.; Retailleau, P.; Ziessel, R. Angew. Chem., Int. Ed. 2008, 47, 8876– 8880 DOI: 10.1002/anie.200803131
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  15. 15

    CCDC 1532160 (racemate 1), 1532161 (enantiopure Sa-1), 1532162 (racemate 2), and 1532163 (enantiopure Ra-2) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre.

    There is no corresponding record for this reference.
  16. 16
    Morse, G. E.; Gong, I.; Kawar, Y.; Lough, A. J.; Bender, T. P. Cryst. Growth Des. 2014, 14, 2138– 2147 DOI: 10.1021/cg401475b
    [ACS Full Text ACS Full Text], [CAS], Google Scholar
    16
    Crystal and Solid-State Arrangement Trends of Halogenated Boron Subphthalocyanines
    Morse, Graham E.; Gong, Ivan; Kawar, Yazan; Lough, Alan J.; Bender, Timothy P.
    Crystal Growth & Design (2014), 14 (5), 2138-2147CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)
    A series of new crystal structures for the boron subphthalocyanine (BsubPc) derivs. chloro hexachloro BsubPc (Cl-Cl6BsubPc), chloro dodecachloro BsubPc (Cl-Cl12BsubPc), bromo/chloro hexachloro BsubPc (Br0.27|Cl0.73-Cl6BsubPc), bromo dodecachloro BsubPc (Br-Cl12BsubPc), and pentafluorophenoxy dodecachloro BsubPc (F5PhO-Cl12BsubPc) are reported. By combining these new crystal structures with a series of previously published structures into a comprehensive study, we have outlined several new structure crystal property/solid-state arrangement relationships for this expanded list of BsubPc derivs. Parameters that were examd. to establish the relationships include (a) geometric descriptors of the BsubPc mol. structure including the bowl shape of the BsubPcs; (b) molar d. of the crystals; and (c) void vol. fraction (Φ). Variations in the peripheral substituents (from hydrogen to fluorine and chlorine) were found to have a profound effect on the solid-state arrangement. No significant changes were noted when the axial substituent was varied from chlorine to bromine, whereas replacement of the axial halide with a pentafluorophenoxy fragment resulted in a notable change (as expected). It was also found that Cl-C12BsubPc (and its derivs.) had a high tendency to co-crystallize with solvents (form solvates), which resulted in a significantly different solid-state arrangement. We believe the observations detailed in this paper will lead to routes to engineer the crystn. of BsubPcs to facilitate tailored solid-state arrangement and properties.
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    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXks1GntLw%253D&md5=5631277cc68ae2759e7c7b00bd9ab539
  17. 17

    A qualitative experiment addressing the stability of atropisomer Ra-2 towards racemization has been carried out (Figure S12.1). Further studies aiming at determining the energy barrier and activation parameters for the interconversion between the Sa and Ra atropisomers of 1 and 2 are currently in progress in our laboratories and will be reported in due course.

    There is no corresponding record for this reference.
  18. 18
    Yamada, M.; Rivera-Fuentes, P.; Schweizer, W. B.; Diederich, F. Angew. Chem., Int. Ed. 2010, 49, 3532– 3535 DOI: 10.1002/anie.200906853
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  19. 19
    Guilleme, J.; González-Rodríguez, D.; Torres, T. Angew. Chem., Int. Ed. 2011, 50, 3506– 3509 DOI: 10.1002/anie.201007240
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  20. 20
    Kato, S.; Diederich, F. Chem. Commun. 2010, 46, 1994– 2006 DOI: 10.1039/b926601a
    [Crossref], [PubMed], [CAS], Google Scholar
    20
    Non-planar push-pull chromophores
    Kato, Shin-ichiro; Diederich, Francois
    Chemical Communications (Cambridge, United Kingdom) (2010), 46 (12), 1994-2006CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    A review. The development of a unique class of non-planar push-pull chromophores by means of [2+2] cycloaddn., followed by cycloreversion, of electron-deficient olefins, such as tetracyanoethene (TCNE), 7,7,8,8-tetracyanoquinodimethane (TCNQ) and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), as well as dicyanovinyl (DCV) and tricyanovinyl (TCV) derivs., to donor-substituted alkynes is explored in this feature article. This high-yielding, "click-chem."-type transformation with acetylenic dendrimers affords dendritic electron sinks capable of multiple electron uptake within a narrow potential range. An [AB]-type oligomer with a dendralene backbone was synthesized by a one-pot, multi-component cascade reaction of polyyne oligomers with TCNE and tetrathiafulvalene (TTF). In most cases, the resulting chromophores feature intense intramol. charge-transfer bands extending far into the near IR region and some of them display high third-order optical nonlinearities. Despite substitution with strong donors, the electron-withdrawing moieties in the new chromophores remain potent acceptors and a no. of them display pos. first redn. potentials (vs. the ferrocenium/ferrocene (Fc+/Fc) couple in CH2Cl2), which rival those of parent TCNE, TCNQ and F4-TCNQ. The non-planarity of the chromophores strongly enhances their phys. properties when compared to planar push-pull analogs. They feature high soly., thermal stability and sublimability, which enables formation of amorphous, high-optical-quality thin films by vapor phase deposition and makes them interesting as advanced functional materials for novel opto-electronic devices.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXjtVSntr8%253D&md5=d5e837a47fb90addd55e071f8f176689
  21. 21
    Kimura, K.; Tsubomura, H.; Nagakura, S. Bull. Chem. Soc. Jpn. 1964, 37, 1336– 1346 DOI: 10.1246/bcsj.37.1336
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  22. 22

    Singlet excited-state energies of SubPc were calculated as an average value by means of the following eq:where λmax(abs) is the absorption maximum at the longest wavelength and λmax(em) is the fluorescence maximum at the shortest wavelength.

    There is no corresponding record for this reference.
  23. 23

    Please note that such differences between the excitation and the absorption spectra are not observed in the case of SubPc–ethynyl–aniline conjugates 3 and 4 (Figure S10.8).

    There is no corresponding record for this reference.
  24. 24
    (a) Gordon, M.; Ware, W. R., Eds. The Exciplex; Academic Press: New York, 1975.
    Google Scholar
    There is no corresponding record for this reference.
    (b) Verhoeven, J. W. Pure Appl. Chem. 1996, 68, 2223– 2286 DOI: 10.1351/pac199668122223
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  25. 25
    It is important to notice that the formation of an excited dimer species (i.e., an excimer) through excited-state interactions between two identical molecular entities of 2 can be excluded here. Excimer fluorescence is concentration-dependent, whereas in the case of 2 the broad, featureless fluorescence is already observed at concentrations less than 10–6 M (Figure S10.11). In addition, usually, the maximum of the excimer fluorescence is only weakly solvent-dependent (Turro, N. J.; Ramamurthy, V.; Scaiano, J. C. Modern Molecular Photochemistry of Organic Molecules; University Science Books: Sausalito, CA, 2010; pp 1– 1110), whereas in the case of 2, a strong solvent polarity effect is noticed. Based on these findings, and considering that SubPcs are not susceptible to aggregation in solution, an intermolecular excited dimer formation is unfeasible.
    Google Scholar
    There is no corresponding record for this reference.
  26. 26
    Aydemir, M.; Jankus, V.; Dias, F. B.; Monkman, A. P. J. Phys. Chem. C 2015, 119, 5855– 5863 DOI: 10.1021/jp512467g
    [ACS Full Text ACS Full Text], Google Scholar
    There is no corresponding record for this reference.
  27. 27
    Radiative Decay Engineering; Lakowicz, J. R.; Geddes, C. D., Eds.; Springer: New York, 2005.
    Google Scholar
    There is no corresponding record for this reference.
  28. 28

    It is important to consider that little, or no, electronic communication between the two DCV units of the TCBD moiety in 1, 2, and 7 is expected to occur in the ground state because the two DCVs are placed in an almost perpendicular arrangement, as inferred by X-ray crystal structure determination.

    There is no corresponding record for this reference.
  29. 29

    ΦΔ values were determined with respect to F12SubPc reference compound 8, which has a ΦΔ of 0.31 in toluene.

    There is no corresponding record for this reference.
  30. 30
    Feng, L.; Rudolf, M.; Trukhina, O.; Slanina, Z.; Uhlik, F.; Lu, X.; Torres, T.; Guldi, D. M.; Akasaka, T. Chem. Commun. 2015, 51, 330– 333 DOI: 10.1039/C4CC08072F
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
  31. 31
    Rudolf, M.; Trukhina, O.; Perles, J.; Feng, L.; Akasaka, T.; Torres, T.; Guldi, D. M. Chem. Sci. 2015, 6, 4141– 4147 DOI: 10.1039/C5SC00223K
    [Crossref], [PubMed], [CAS], Google Scholar
    31
    Taming C60 fullerene: tuning intramolecular photoinduced electron transfer process with subphthalocyanines
    Rudolf, Marc; Trukhina, Olga; Perles, Josefina; Feng, Lai; Akasaka, Takeshi; Torres, Tomas; Guldi, Dirk M.
    Chemical Science (2015), 6 (7), 4141-4147CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
    Two subphthalocyanine-C60 conjugates have been prepd. by means of the 1,3-dipolar cycloaddn. reaction of (perfluoro) or hexa(pentylsulfonyl) electron deficient subphthalocyanines to C60. Comprehensive assays regarding the electronic features - in the ground and excited state - of the resulting conjugates revealed energy and electron transfer processes upon photoexcitation. Most important is the unambiguous evidence - in terms of time-resolved spectroscopy - of an ultrafast oxidative electron transfer evolving from C60 to the photoexcited subphthalocyanines. This is, to the best of our knowledge, the first case of an intramol. oxidn. of C60 within electron donor-acceptor conjugates by means of only photoexcitation.
    >> More from SciFinder ®
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  32. 32

    Please note that the electrochemistry in nonaqueous media such as o-DCB may be influenced by protonation/deprotonation occurring upon the initial redox process:

    Xue, S.; Ou, Z.; Ye, L.; Lu, G.; Fang, Y.; Jiang, X.; Kadish, K. M. Chem. - Eur. J. 2015, 21, 2651– 2661 DOI: 10.1002/chem.201405570
    [Crossref], [PubMed], [CAS], Google Scholar
    32
    Effect of Solvent and Protonation/Deprotonation on Electrochemistry, Spectroelectrochemistry and Electron-Transfer Mechanisms of N-Confused Tetraarylporphyrins in Nonaqueous Media
    Xue, Songlin; Ou, Zhongping; Ye, Lina; Lu, Guifen; Fang, Yuanyuan; Jiang, Xiaoqin; Kadish, Karl M.
    Chemistry - A European Journal (2015), 21 (6), 2651-2661CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A series of N-confused free-base meso-substituted tetraarylporphyrins was investigated by electrochem. and spectroelectrochem. in nonaq. media contg. 0.1 M tetra-n-butylammonium perchlorate (TBAP) and added acid or base. The investigated compds. were represented as (XPh)4NcpH2, in which "Ncp" is the N-confused porphyrin macrocycle and X is a OCH3, CH3, H, or Cl substituent on the para position of each meso-Ph ring of the macrocycle. Two distinct types of UV/Vis spectra were initially obsd. depending upon solvent, one corresponding to an inner-2H form and the other to an inner-3H form of the porphyrin. Both forms have an inverted pyrrole with a carbon inside the cavity and a nitrogen on the periphery of the π-system. Each porphyrin undergoes multiple irreversible redns. and oxidns. The first one-electron addn. and first one-electron abstraction are located on the porphyrin π-ring system to give π-anion and π-cation radicals with a potential sepn. of 1.52 to 1.65 V between the two processes, but both electrogenerated products are unstable and undergo a rapid chem. reaction to give new electroactive species, which were characterized in the present study. The effect of the solvent and protonation/deprotonation reactions on the UV/Vis spectra, redox potentials and redn./oxidn. mechanisms is discussed with comparisons made to data and mechanisms for the structurally related free-base corroles and porphyrins.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXitFaiurzJ&md5=7716b4d7db60d393887a639369a09397

    In case of 6, the F12SubPc•– radical anion initially formed upon electrochemical reduction is probably unstable on the spectroelectrochemical time scale evolving toward a deprotonated/protonated species as a byproduct of the electrochemical reduction. Therefore, the spectroelectrochemical features of 6•– are blurred and do not resemble the clear and sharp transient absorption features of the F12SubPc•– radical anion.

  33. 33
    (a) Sosorev, A. Y.; Paraschuk, D. Y. Isr. J. Chem. 2014, 54, 650– 673 DOI: 10.1002/ijch.201400063
    [Crossref], [CAS], Google Scholar
    33a
    Charge-Transfer Complexes of Conjugated Polymers
    Sosorev, Andrey Yu.; Paraschuk, Dmitry Yu.
    Israel Journal of Chemistry (2014), 54 (5-6), 650-673CODEN: ISJCAT; ISSN:0021-2148. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A review. Donor-acceptor blends of conjugated polymers (CPs) are workhorse materials for the state-of-the-art polymer solar cells. Although earlier it was suggested that charge transfer in these blends occurred only in the excited electronic state, a body of evidence for ground-state charge transfer and the corresponding charge-transfer complex (CTC) formation has been reported in the last decade. In some CP:acceptor blends, the CTC is pronounced and can be noticed visually as a color change, while in more common CP:fullerene blends it is very weak. However, in both, the CTC governs charge sepn., which is the key photophys. process for org. solar cells, through so-called charge-transfer states. Moreover, the pronounced CTC can substantially modify the blend properties: extend the blend absorption in the red and IR regions, change the morphol. to facilitate donor-acceptor intermixing, stimulate polymer self-organization and ordering, and increase the polymer photooxidn. stability. Addn. of one of the strongest org. acceptors, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), to the CP:fullerene blend is an example of org. doping (a CTC with full charge transfer), improving the blend structural and electronic properties and finally the solar cell performance. In this review, we summarize the current knowledge on CTCs in various CP:acceptor blends and the impact of CTC on the blend properties and the device performance.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXps1ymurs%253D&md5=c066ffe11be78e4b920434dbfe671d1a
    (b) Deibel, C.; Strobel, T.; Dyakonov, V. Adv. Mater. 2010, 22, 4097– 4111 DOI: 10.1002/adma.201000376
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
    (c) Akaike, K.; Kanai, K.; Ouchi, Y.; Seki, K. Adv. Funct. Mater. 2010, 20, 715– 721 DOI: 10.1002/adfm.200901585
    [Crossref], Google Scholar
    There is no corresponding record for this reference.
    (d) Benson-Smith, J. J.; Goris, L.; Vandewal, K.; Haenen, K.; Manca, J. V.; Vanderzande, D.; Bradley, D. D. C.; Nelson, J. Adv. Funct. Mater. 2007, 17, 451– 457 DOI: 10.1002/adfm.200600484
    [Crossref], Google Scholar
    There is no corresponding record for this reference.

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  32. Faizal Khan, Youngwoo Jang, Yuvraj Patil, Rajneesh Misra, Francis D'Souza. Photoinduced Charge Separation Prompted Intervalence Charge Transfer in a Bis(thienyl)diketopyrrolopyrrole Bridged Donor‐TCBD Push‐Pull System. Angewandte Chemie 2021, 133 (37) , 20681-20690. https://doi.org/10.1002/ange.202108293
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  36. Giovanni Bottari, Gema de la Torre, Dirk M. Guldi, Tomás Torres. An exciting twenty-year journey exploring porphyrinoid-based photo- and electro-active systems. Coordination Chemistry Reviews 2021, 428 , 213605. https://doi.org/10.1016/j.ccr.2020.213605
  37. Indresh S. Yadav, Ajyal Z. Alsaleh, Rajneesh Misra, Francis D'Souza. Charge stabilization via electron exchange: excited charge separation in symmetric, central triphenylamine derived, dimethylaminophenyl–tetracyanobutadiene donor–acceptor conjugates. Chemical Science 2021, 12 (3) , 1109-1120. https://doi.org/10.1039/D0SC04648E
  38. Mathias Dowds, Mogens Brøndsted Nielsen. Controlling the optical properties of boron subphthalocyanines and their analogues. Molecular Systems Design & Engineering 2021, 6 (1) , 6-24. https://doi.org/10.1039/D0ME00150C
  39. Dilip Pinjari, Ajyal Z. Alsaleh, Yuvraj Patil, Rajneesh Misra, Francis D'Souza. Interfacing High‐Energy Charge‐Transfer States to a Near‐IR Sensitizer for Efficient Electron Transfer upon Near‐IR Irradiation. Angewandte Chemie International Edition 2020, 59 (52) , 23697-23705. https://doi.org/10.1002/anie.202013036
  40. Dilip Pinjari, Ajyal Z. Alsaleh, Yuvraj Patil, Rajneesh Misra, Francis D'Souza. Interfacing High‐Energy Charge‐Transfer States to a Near‐IR Sensitizer for Efficient Electron Transfer upon Near‐IR Irradiation. Angewandte Chemie 2020, 132 (52) , 23905-23913. https://doi.org/10.1002/ange.202013036
  41. Pablo Simón Marqués, José María Andrés Castán, Benedito A. L. Raul, Giacomo Londi, Ivan Ramirez, Maxim S. Pshenichnikov, David Beljonne, Karsten Walzer, Martin Blais, Magali Allain, Clément Cabanetos, Philippe Blanchard. Triphenylamine/Tetracyanobutadiene‐Based π‐Conjugated Push–Pull Molecules End‐Capped with Arene Platforms: Synthesis, Photophysics, and Photovoltaic Response. Chemistry – A European Journal 2020, 26 (69) , 16422-16433. https://doi.org/10.1002/chem.202002810
  42. Johannes Zirzlmeier, Giulia Lavarda, Henrik Gotfredsen, Ilias Papadopoulos, Lan Chen, Timothy Clark, Rik R. Tykwinski, Tomás Torres, Dirk M. Guldi. Modulating the dynamics of Förster resonance energy transfer and singlet fission by variable molecular spacers. Nanoscale 2020, 12 (45) , 23061-23068. https://doi.org/10.1039/D0NR06285E
  43. Giulia Lavarda, Nicholus Bhattacharjee, Giuseppe Brancato, Tomás Torres, Giovanni Bottari. Enabling Racemization of Axially Chiral Subphthalocyanine‐Tetracyanobutadiene‐Aniline Enantiomers by Triplet State Photogeneration. Angewandte Chemie International Edition 2020, 59 (47) , 21224-21229. https://doi.org/10.1002/anie.202010133
  44. Giulia Lavarda, Nicholus Bhattacharjee, Giuseppe Brancato, Tomás Torres, Giovanni Bottari. Enabling Racemization of Axially Chiral Subphthalocyanine‐Tetracyanobutadiene‐Aniline Enantiomers by Triplet State Photogeneration. Angewandte Chemie 2020, 132 (47) , 21410-21415. https://doi.org/10.1002/ange.202010133
  45. Line Broløs, Martin Drøhse Kilde, Mogens Brøndsted Nielsen. Novel synthetic strategy towards subphthalocyanine-functionalized acetylenic scaffolds via various dibromo-enynes. Organic & Biomolecular Chemistry 2020, 18 (31) , 6077-6085. https://doi.org/10.1039/D0OB00988A
  46. A. R. Gataullina, R. R. Gataullin. Axial Chiral Metal Complexes, Carbo- and Heterocycles: Modern Synthesis Strategies and Examples of the Effect of Atropoisomerism on the Structure of Reaction Products. Russian Journal of General Chemistry 2020, 90 (7) , 1255-1284. https://doi.org/10.1134/S1070363220070130
  47. Shin-ichiro Kato, Tomokazu Kijima, Yoshihito Shiota, Tsukasa Abe, Satoshi Kuwako, Hidenori Miyauchi, Naoki Yoshikawa, Koji Yamamoto, Kazunari Yoshizawa, Toshitada Yoshihara, Seiji Tobita, Yosuke Nakamura. Chemical transformations of push–pull fluorenones: push–pull dibenzodicyanofulvenes as well as fluorenone– and dibenzodicyanofulvene–tetracyanobutadiene conjugates. Organic & Biomolecular Chemistry 2020, 18 (22) , 4198-4209. https://doi.org/10.1039/C9OB02706H
  48. Madhurima Poddar, Youngwoo Jang, Rajneesh Misra, Francis D'Souza. Excited‐State Electron Transfer in 1,1,4,4‐Tetracyanobuta‐1,3‐diene (TCBD)‐ and Cyclohexa‐2,5‐diene‐1,4‐diylidene‐Expanded TCBD‐Substituted BODIPY‐Phenothiazine Donor–Acceptor Conjugates. Chemistry – A European Journal 2020, 26 (30) , 6869-6878. https://doi.org/10.1002/chem.202000346
  49. Anh Thy Bui, Clotilde Philippe, Maxime Beau, Nicolas Richy, Marie Cordier, Thierry Roisnel, Loïc Lemiègre, Olivier Mongin, Frédéric Paul, Yann Trolez. Synthesis, characterization and unusual near-infrared luminescence of 1,1,4,4-tetracyanobutadiene derivatives. Chemical Communications 2020, 56 (24) , 3571-3574. https://doi.org/10.1039/C9CC09560H
  50. Christoph Schierl, Virtudes Pardo, Giovanni Bottari, Dirk M. Guldi, Tomas Torres. Cyclopenta[hi]aceanthrylene Decorated with Multiple and Long Alkoxy Chains: Physicochemical Properties and Single-Walled Carbon Nanotubes’ Exfoliation Capability. ECS Journal of Solid State Science and Technology 2020, 9 (5) , 051011. https://doi.org/10.1149/2162-8777/ab9a5a
  51. Kim A. Winterfeld, Giulia Lavarda, Julia Guilleme, Dirk M. Guldi, Tomás Torres, Giovanni Bottari. Subphthalocyanine–tetracyanobuta-1,3-diene–aniline conjugates: stereoisomerism and photophysical properties. Chemical Science 2019, 10 (48) , 10997-11005. https://doi.org/10.1039/C9SC03970H
  52. Esmeralda Bukuroshi, Jenya Vestfrid, Zeev Gross, Timothy P. Bender. Fluorinated boron subphthalocyanines: Lewis acid based templating chemistry facilitates random halide exchange, and fluoride versus chloride affects the basic photophysical properties and the solid-state arrangement. New Journal of Chemistry 2019, 43 (42) , 16730-16737. https://doi.org/10.1039/C9NJ04093E
  53. Christoph Schierl, Wiebke Alex, Luis M. Mateo, Beatriz Ballesteros, Daiki Shimizu, Atsuhiro Osuka, Tomas Torres, Dirk M. Guldi, Giovanni Bottari. Quadrupolar Cyclopenta[ hi ]aceanthrylene‐Based Electron Donor‐Acceptor‐Donor Conjugates: Charge Transfer versus Charge Separation. Angewandte Chemie International Edition 2019, 58 (41) , 14644-14652. https://doi.org/10.1002/anie.201906206
  54. Christoph Schierl, Wiebke Alex, Luis M. Mateo, Beatriz Ballesteros, Daiki Shimizu, Atsuhiro Osuka, Tomas Torres, Dirk M. Guldi, Giovanni Bottari. Quadrupolar Cyclopenta[ hi ]aceanthrylene‐Based Electron Donor‐Acceptor‐Donor Conjugates: Charge Transfer versus Charge Separation. Angewandte Chemie 2019, 131 (41) , 14786-14794. https://doi.org/10.1002/ange.201906206
  55. Jinling Miao, Yong Nie, Huihui Du, Xiaojun Yang, Chuanhao Zhang, Hong Yan. Tunable excitation-dependent emissions in mixed-ligand Cd(II) complexes. Polyhedron 2019, 171 , 338-343. https://doi.org/10.1016/j.poly.2019.07.028
  56. Yuriy V. Zatsikha, Rachel K. Swedin, Andrew T. Healy, Philip C. Goff, Natalia O. Didukh, Tanner S. Blesener, Mathew Kayser, Yuriy P. Kovtun, David A. Blank, Victor N. Nemykin. Synthesis, Characterization, and Electron‐Transfer Properties of Ferrocene–BODIPY–Fullerene Near‐Infrared‐Absorbing Triads: Are Catecholopyrrolidine‐Linked Fullerenes a Good Architecture to Facilitate Electron‐Transfer?. Chemistry – A European Journal 2019, 25 (35) , 8401-8414. https://doi.org/10.1002/chem.201901225
  57. Rekha Sharma, Michael B. Thomas, Rajneesh Misra, Francis D'Souza. Strong Ground‐ and Excited‐State Charge Transfer in C 3 ‐Symmetric Truxene‐Derived Phenothiazine‐Tetracyanobutadine and Expanded Conjugates. Angewandte Chemie 2019, 131 (13) , 4394-4399. https://doi.org/10.1002/ange.201814388
  58. Rekha Sharma, Michael B. Thomas, Rajneesh Misra, Francis D'Souza. Strong Ground‐ and Excited‐State Charge Transfer in C 3 ‐Symmetric Truxene‐Derived Phenothiazine‐Tetracyanobutadine and Expanded Conjugates. Angewandte Chemie International Edition 2019, 58 (13) , 4350-4355. https://doi.org/10.1002/anie.201814388
  59. Giulia Lavarda, Johannes Zirzlmeier, Marco Gruber, Parisa R. Rami, Rik R. Tykwinski, Tomás Torres, Dirk M. Guldi. Tuning Intramolecular Förster Resonance Energy Transfer and Activating Intramolecular Singlet Fission. Angewandte Chemie International Edition 2018, 57 (50) , 16291-16295. https://doi.org/10.1002/anie.201808652
  60. Giulia Lavarda, Johannes Zirzlmeier, Marco Gruber, Parisa R. Rami, Rik R. Tykwinski, Tomás Torres, Dirk M. Guldi. Feinabstimmung von intramolekularem resonantem Förster-Energietransfer und Aktivierung intramolekularer Singulettspaltung. Angewandte Chemie 2018, 130 (50) , 16528-16533. https://doi.org/10.1002/ange.201808652
  61. Henrik Gotfredsen, Timo Neumann, Freja Eilsø Storm, Alberto Viñas Muñoz, Martyn Jevric, Ole Hammerich, Kurt V. Mikkelsen, Marina Freitag, Gerrit Boschloo, Mogens Brøndsted Nielsen. Donor−Acceptor‐Functionalized Subphthalocyanines for Dye‐Sensitized Solar Cells. ChemPhotoChem 2018, 2 (11) , 976-985. https://doi.org/10.1002/cptc.201800135
  62. Chunhui Duan, David Guzmán, Fallon J. M. Colberts, René A. J. Janssen, Tomás Torres. Subnaphthalocyanines as Electron Acceptors in Polymer Solar Cells: Improving Device Performance by Modifying Peripheral and Axial Substituents. Chemistry – A European Journal 2018, 24 (24) , 6339-6343. https://doi.org/10.1002/chem.201800596
  63. Raúl García, Joaquín Calbo, Rafael Viruela, M. Ángeles Herranz, Enrique Ortí, Nazario Martín. The Role of Planarity versus Nonplanarity in the Electronic Communication of TCAQ‐Based Push–Pull Chromophores. ChemPlusChem 2018, 83 (4) , 300-307. https://doi.org/10.1002/cplu.201700553
  64. Tsuyoshi Michinobu, François Diederich. Die [2+2]‐Cycloadditions‐Retroelektrocyclisierungs(CA‐RE)‐Klick‐Reaktion: ein einfacher Zugang zu molekularen und polymeren Push‐pull‐Chromophoren. Angewandte Chemie 2018, 130 (14) , 3612-3638. https://doi.org/10.1002/ange.201711605
  65. Tsuyoshi Michinobu, François Diederich. The [2+2] Cycloaddition‐Retroelectrocyclization (CA‐RE) Click Reaction: Facile Access to Molecular and Polymeric Push‐Pull Chromophores. Angewandte Chemie International Edition 2018, 57 (14) , 3552-3577. https://doi.org/10.1002/anie.201711605
  66. M. Ángel Revuelta-Maza, Ettore Fazio, Gema de la Torre, Tomás Torres. Metallo-organic ensembles of tritopic subphthalocyanine ligands. Journal of Porphyrins and Phthalocyanines 2017, 21 (12) , 782-789. https://doi.org/10.1142/S1088424617500882
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  • Abstract

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    Scheme 1

    Scheme 1. Synthesis of SubPc–TCBD–Aniline Conjugates 1 and 2a
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    Scheme aConditions: (i) 4-ethynyl-N,N′-dimethylaniline, EtMgBr, anhydrous THF, 60 °C; (ii) tetracyanoethylene, anhydrous THF, room temperature.

    Figure 1

    Figure 1. Lateral view (with respect to the SubPc–TCBD–aniline B–C bond) of the X-ray crystal structure of atropisomers (a) Ra-2 and (b) Sa-2 in F12SubPc–TCBD–aniline racemate 2. Lateral (top) and top view (bottom) (with respect to the SubPc–TCBD–aniline B–C bond) of the X-ray crystal structure of atropisomers (c) Sa-1 and (d) Ra-2 (for a detailed account on how to determine the atropisomers’ absolute configuration, see section 4 in the Supporting Information). In the top view representations, in order to facilitate the visualization of the atropisomers, (i) one of the two atropisomers was colored in red (in b), and (ii) solid colors have been used to fill the SubPcs (light red in b, light blue in b and c) and the aniline ring (light purple). Carbon atoms are in light blue, nitrogen atoms in dark blue, boron atoms in light pink, hydrogen atoms in white, and fluorine atoms in yellow. In (c), chloroform molecules of crystallization have been omitted for clarity.

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    Figure 2

    Figure 2. (a) HPLC chromatogram of F12SubPc–TCBD–aniline racemate 2 with peaks corresponding to atropisomers Sa-2 (blue trace) and Ra-2 (red trace). The area underneath the blue and red traces is 50.2 and 49.8%, respectively. (b) Circular dichroism spectra of atropisomers Sa-2 (blue spectrum) and Ra-2 (red spectrum) in CHCl3 (atropisomers’ concentration = 3.5 × 10–5 M).

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    Figure 3

    Figure 3. Normalized steady-state absorption (black) and fluorescence spectra (red) of (a) H12SubPc–TCBD–aniline conjugate 1 (λex = 530 nm, c = 2.05 × 10–6 M) and (b) F12SubPc–TCBD–aniline conjugate 2 (λex = 550 nm, c = 8.90 × 10–6 M) recorded in toluene.

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    Figure 4

    Figure 4. Normalized steady-state absorption (black) and excitation spectra (red) of (a) H12SubPc–TCBD–aniline conjugate 1 (λem = 630 nm, c = 1.09 × 10–6 M) and (b) F12SubPc–TCBD–aniline conjugate 2 (λem = 680 nm, c = 1.09 × 10–6 M) recorded in toluene.

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    Figure 5

    Figure 5. Fluorescence and (inset) normalized (with respect to the SubPc local emission at 612 nm) fluorescence spectra of F12SubPc–TCBD–aniline conjugate 2 (λex = 550 nm, c = 2.0 × 10–5 M) recorded upon heating up from 5 to 65 °C in chlorobenzene.

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    Figure 6

    Figure 6. Evolution associated spectra and associated time-dependent amplitudes (inset) obtained upon femtosecond flash photolysis (550 nm, 150 nJ) of F12SubPc–TCBD–aniline conjugate 2 (2 × 10–5 M) in argon-saturated toluene monitoring the exciplex formation and decay processes.

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    Figure 7

    Figure 7. Energy level diagrams of F12SubPc–TCBD–aniline conjugate 2 reflecting the energetic pathways in (a) toluene and (b) benzonitrile after excitation of the F12SubPc (λex = 550 nm, green arrow) and TCBD–aniline band (λex = 458 nm, blue arrow). Red wavy arrow refers to fluorescence emission, whereas black lines refer to nonradiative processes.

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  • References

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    This article references 33 other publications.

    1. 1
      Molecular Mechanisms of Photosynthesis; Blankenship, R. E., Ed.; Blackwell Science: Oxford, UK, 2002.
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    2. 2
      (a) Special Issue on Artificial Photosynthesis and Solar Fuels. Acc. Chem. Res. 2009, 42, 1859– 2029.
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
      (b) Mishra, A.; Bäuerle, P. Angew. Chem., Int. Ed. 2012, 51, 2020– 2067 DOI: 10.1002/anie.201102326
      [Crossref], [CAS], Google Scholar
      2b
      Small Molecule Organic Semiconductors on the Move: Promises for Future Solar Energy Technology
      Mishra, Amaresh; Baeuerle, Peter
      Angewandte Chemie, International Edition (2012), 51 (9), 2020-2067CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A review. This article, written from an org. chemist's point of view, provides an up-to-date overview of org. solar cells based on small mols. or oligomers as absorbers and describes devices that incorporate planar-heterojunctions and bulk heterojunctions between a donor (p-type semiconductor) and an acceptor (n-type semiconductor) material. The article pays particular attention to the design and development of mol. materials and their performance in corresponding devices. In recent years, a substantial amt. of both, academic and industrial research, has been directed towards org. solar cells, in an effort to develop new materials and to improve their tunability, processability, power conversion efficiency, and stability. On the eve of commercialization of org. solar cells, this review provides an overview of efficiencies attained with small mols./oligomers in org. solar cells and summarizes materials and device concepts developed over the last decade. Approaches to enhancing the efficiency of org. solar cells are analyzed.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xitlygs7g%253D&md5=3bd032ed84f6c2a11c7f6d8efb770901
      (c) Fukuzumi, S.; Ohkubo, K.; Suenobu, T. Acc. Chem. Res. 2014, 47, 1455– 1464 DOI: 10.1021/ar400200u
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      2c
      Long-Lived Charge Separation and Applications in Artificial Photosynthesis
      Fukuzumi, Shunichi; Ohkubo, Kei; Suenobu, Tomoyoshi
      Accounts of Chemical Research (2014), 47 (5), 1455-1464CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
      A review. Researchers have long been interested in replicating the reactivity that occurs in photosynthetic organisms. To mimic the long-lived charge sepns. characteristic of the reaction center in photosynthesis, researchers have applied the Marcus theory to design synthetic multistep electron-transfer (ET) systems. In this Account, the authors describe their recent research on the rational design of ET control systems, based on models of the photosynthetic reaction center that rely on the Marcus theory of ET. The key to obtaining a long-lived charge sepn. is the careful choice of electron donors and acceptors that have small reorganization energies of ET. In these cases, the driving force of back ET is located in the Marcus inverted region, where the lifetime of the charge-sepd. state lengthens as the driving force of back ET increases. The authors chose porphyrins as electron donors and fullerenes as electron acceptors, both of which have small ET reorganization energies. By linking electron donor porphyrins and electron acceptor fullerenes at appropriate distances, we achieved charge-sepd. states with long lifetimes. The authors could further lengthen the lifetimes of charge-sepd. states by mixing a variety of components, such as a terminal electron donor, an electron mediator, and an electron acceptor, mimicking both the photosynthetic reaction center and the multistep photoinduced ET that occurs there. However, each step in multistep ET loses a fraction of the initial excitation energy during the long-distance charge sepn. To overcome this drawback in multistep ET systems, the authors used designed new systems where we could finely control the redox potentials and the geometry of simple donor-acceptor dyads. These modifications resulted in a small ET reorganization energy and a high-lying triplet excited state. The authors most successful example, 9-mesityl-10-methylacridinium ion (Acr+-Mes), can undergo a fast photoinduced ET from the mesityl (Mes) moiety to the singlet excited state of the acridinium ion moiety (Acr+) with extremely slow back ET. The high-energy triplet charge-sepd. state is located deep in the Marcus inverted region, and the authors have detected the structural changes during the photoinduced ET in this system using x-ray crystallog. To increase the efficiency of both the light-harvesting and photoinduced ET, the authors assembled the Acr+-Mes dyads on gold nanoparticles to bring them in closer proximity to one another. The authors can also incorporate Acr+-Mes mols. within nanosized mesoporous silica-alumina. In contrast to the densely assembled dyads on gold nanoparticles, each Acr+-Mes mol. in silica-alumina is isolated in the mesopore, which inhibits the bimol. back ET and leads to longer lifetimes in soln. at room temp. than the natural photosynthetic reaction center. Acr+-Mes and related compds. act as excellent org. photocatalysts and facilitate a variety of reactions such as oxygenation, bromination, carbon-carbon bond formation, and hydrogen evolution reactions.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXntlKnsb8%253D&md5=483d15654c5ed67b268b97396d092527
      (d) Hammarström, L. Acc. Chem. Res. 2015, 48, 840– 850 DOI: 10.1021/ar500386x
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      2d
      Accumulative charge separation for solar fuels production: coupling light-induced single electron transfer to multielectron catalysis
      Hammarstrom Leif
      Accounts of chemical research (2015), 48 (3), 840-50 ISSN:.
      The conversion and storage of solar energy into a fuel holds promise to provide a significant part of the future renewable energy demand of our societies. Solar energy technologies today generate heat or electricity, while the large majority of our energy is used in the form of fuels. Direct conversion of solar energy to a fuel would satisfy our needs for storable energy on a large scale. Solar fuels can be generated by absorbing light and converting its energy to chemical energy by electron transfer leading to separation of electrons and holes. The electrons are used in the catalytic reduction of a cheap substrate with low energy content into a high-energy fuel. The holes are filled by oxidation of water, which is the only electron source available for large scale solar fuel production. Absorption of a single photon typically leads to separation of a single electron-hole pair. In contrast, fuel production and water oxidation are multielectron, multiproton reactions. Therefore, a system for direct solar fuel production must be able to accumulate the electrons and holes provided by the sequential absorption of several photons in order to complete the catalytic reactions. In this Account, the process is termed accumulative charge separation. This is considerably more complicated than charge separation on a single electron level and needs particular attention. Semiconductor materials and molecular dyes have for a long time been optimized for use in photovoltaic devices. Efforts are made to develop new systems for light harvesting and charge separation that are better optimized for solar fuel production than those used in the early devices presented so far. Significant progress has recently been made in the discovery and design of better homogeneous and heterogeneous catalysts for solar fuels and water oxidation. While the heterogeneous ones perform better today, molecular catalysts based on transition metal complexes offer much greater tunability of electronic and structural properties, they are typically more amenable to mechanistic analysis, and they are small and therefore require less material. Therefore, they have arguably greater potential as future efficient catalysts but must be efficiently coupled to accumulative charge separation. This Account discusses accumulative charge separation with focus on molecular and molecule-semiconductor hybrid systems. The coupling between charge separation and catalysis involves many challenges that are often overlooked, and they are not always apparent when studying water oxidation and fuel formation as separate half-reactions with sacrificial agents. Transition metal catalysts, as well as other multielectron donors and acceptors, cycle through many different states that may quench the excited sensitizer by nonproductive pathways. Examples where this has been shown, often with ultrafast rates, are reviewed. Strategies to avoid these competing energy-loss reactions and still obtain efficient coupling of charge separation to catalysis are discussed. This includes recent examples of dye-sensitized semiconductor devices with molecular catalysts and dyes that realize complete water splitting, albeit with limited efficiency.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC2MrkslGqsw%253D%253D&md5=653b29826f7380d895c143a83c96a684
    3. 3
      (a) Claessens, C. G.; Gonzalez-Rodríguez, D.; Torres, T. Chem. Rev. 2002, 102, 835– 853 DOI: 10.1021/cr0101454
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
      (b) Claessens, C. G.; Gonzalez-Rodríguez, D.; Rodríguez-Morgade, M. S.; Medina, A.; Torres, T. Chem. Rev. 2014, 114, 2192– 2277 DOI: 10.1021/cr400088w
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    4. 4
      (a) Gonzalez-Rodríguez, D.; Torres, T.; Guldi, D. M.; Rivera, J.; Herranz, M. A.; Echegoyen, L. J. Am. Chem. Soc. 2004, 126, 6301– 6313 DOI: 10.1021/ja039883v
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
      (b) El-Khouly, M. E.; Shim, S. H.; Araki, Y.; Ito, O.; Kay, K.-Y. J. Phys. Chem. B 2008, 112, 3910– 3917 DOI: 10.1021/jp7108658
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
      (c) Gonzalez-Rodríguez, D.; Carbonell, E.; Guldi, D. M.; Torres, T. Angew. Chem., Int. Ed. 2009, 48, 8032– 8036 DOI: 10.1002/anie.200902767
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
      (d) Sanchez-Molina, I.; Claessens, C. G.; Grimm, B.; Guldi, D. M.; Torres, T. Chem. Sci. 2013, 4, 1338– 1344 DOI: 10.1039/c3sc21956a
      [Crossref], [CAS], Google Scholar
      4d
      Trapping fullerenes with jellyfish-like subphthalocyanines
      Sanchez-Molina, I.; Claessens, C. G.; Grimm, B.; Guldi, D. M.; Torres, T.
      Chemical Science (2013), 4 (3), 1338-1344CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
      Six electronically different concave-shaped subphthalocyanines (SubPcs) were prepd. for testing the structural factors governing fullerenes encapsulation. Thus, the supramol. interaction of SubPcs with C60 and C70 fullerenes in soln. was studied by Job's plot and titrn. expts., which yielded quant. information on both the stoichiometry and strength of the complexes in toluene soln. The importance of the electronic nature of the SubPc was demonstrated, as it influences not only the stability of the complex, but also its stoichiometry. Alkyl chains incorporated in hexaalkylthio-substituted SubPcs seem to in some way cooperate in the binding process and influence its kinetics. In the resulting 2:1 complexes, the large absorption cross section of SubPcs throughout the visible part of the spectrum is the beginning of an unidirectional energy transfer to funnel the excited state energy from the periphery (i.e., two SubPcs) to the core (i.e., C60 and C70).
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhvFGqt78%253D&md5=d3f3e411588a16df6ca80c2c270f684f
      (e) Sanchez-Molina, I.; Grimm, B.; Krick Calderon, R. M.; Claessens, C. G.; Guldi, D. M.; Torres, T. J. Am. Chem. Soc. 2013, 135, 10503– 10511 DOI: 10.1021/ja404234n
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    5. 5
      (a) González-Rodríguez, D.; Torres, T.; Olmstead, M. M.; Rivera, J.; Herranz, M. A.; Echegoyen, L.; Atienza-Castellanos, C.; Guldi, D. M. J. Am. Chem. Soc. 2006, 128, 10680– 10681 DOI: 10.1021/ja0632409
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
      (b) Maligaspe, E.; Hauwiller, M. R.; Zatsikha, Y. V.; Hinke, J. A.; Solntsev, P. V.; Blank, D. A.; Nemykin, V. N. Inorg. Chem. 2014, 53, 9336– 9347 DOI: 10.1021/ic5014544
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
      (c) El-Khouly, M. E.; El-Kemary, M. A.; El-Refaey, A.; Kay, K.-Y.; Fukuzumi, S. J. Porphyrins Phthalocyanines 2016, 20, 1148– 1155 DOI: 10.1142/S1088424616500784
      [Crossref], [CAS], Google Scholar
      5c
      Light harvesting subphthalocyanine-ferrocene dyads: Fast electron transfer process studied by femtosecond laser photolysis
      El-Khouly, Mohamed E.; El-Kemary, Maged A.; El-Refaey, Ahmed; Kay, Kwang-Yol; Fukuzumi, Shunichi
      Journal of Porphyrins and Phthalocyanines (2016), 20 (8/11), 1148-1155CODEN: JPPHFZ; ISSN:1088-4246. (World Scientific Publishing Co. Pte. Ltd.)
      Ferrocene-subphthalocyanine dyads characterized, where ferrocene is axially linked with subphthalocyanine at its axial position with the B-O bond through the para and metapositions, namely Fc-pPhO-SubPc (dyad 1) and Fc-mPhO-SubPc (dyad 2). The geometric and electronic structures of 1 and 2 were probed by ab initio B3LYP/6-311G methods. The optimized structures showed that the Fc and SubPc entities are sepd. by 8.42 and 7.40 Å for dyads 1 and 2, resp. The distribution of the highest occupied frontier MO (HOMO) was found to be located on the Fc entity, while the LUMO (LUMO) was located on the SubPc entity, suggesting that the charge-sepd. states of the are Fc+-SubPc-. Upon photoexcitation at the subphthalocyanine unit, both dyads undergo photoinduced electron transfer to form the corresponding charge-sepd. species, Fc+-SubPc-. Based on their redox potentials detd. by cyclic voltammetry technique, the direction of the charge sepn. and the energies of these states have been revealed. Femtosecond transient spectroscopic studies have revealed that a fast charge sepn. of 8.8 × 1010 and 1.2 × 1011 s-1 for 1 and 2, resp., indicating fast charge sepn. in these simple dyads.
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    6. 6
      (a) Xu, H.; Ng, D. K. P. Inorg. Chem. 2008, 47, 7921– 7927 DOI: 10.1021/ic800756h
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
      (b) El-Khouly, M. E.; Ryu, J. B.; Kay, K.-Y.; Ito, O.; Fukuzumi, S. J. Phys. Chem. C 2009, 113, 15444– 15453 DOI: 10.1021/jp904310f
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
      (c) El-Khouly, M. E.; Ju, D. K.; Kay, K.-Y.; D’Souza, F.; Fukuzumi, S. Chem. - Eur. J. 2010, 16, 6193– 6202 DOI: 10.1002/chem.201000045
      [Crossref], [PubMed], [CAS], Google Scholar
      6c
      Supramolecular Tetrad of Subphthalocyanine-Triphenylamine-Zinc Porphyrin Coordinated to Fullerene as an "Antenna-Reaction-Center" Mimic: Formation of a Long-Lived Charge-Separated State in Nonpolar Solvent
      El-Khouly, Mohamed E.; Ju, Dong Kyu; Kay, Kwang-Yol; D'Souza, Francis; Fukuzumi, Shunichi
      Chemistry - A European Journal (2010), 16 (21), 6193-6202, S6193/1-S6193/6CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The authors report formation of a long-lived charge-sepd. state of a self-assembled donor-acceptor tetrad, formed by axial coordination of a fulleropyrrolidine appended with an imidazole coordinating ligand (C60Im) to the Zn center of a subphthalocyanine-triphenylamine-zinc porphyrin (SubPc-TPA-ZnP), as a charge-stabilizing antenna reaction center mimic in toluene. The subphthalocyanine and triphenylamine entities, with their high-energy singlet states, act as an energy-transferring antenna unit to produce a singlet Zn porphyrin. The formation const. for the self-assembled tetrad was detd. to be 1.0×104 M-1, suggesting a moderately stable complex formation. The geometric and electronic structures of the covalently linked SubPc-TPA-ZnP triad and self-assembled SubPc-TPA-ZnP:C60Im tetrad were examd. by using an ab initio B3LYP/6-31G method. The majority of the highest occupied frontier MO was found over the ZnP and TPA entities, whereas the LUMO was located over the fullerene entity, suggesting the formation of the radical-ion pair (SubPc-TPA-ZnP·+:C60Im·-). The redox measurements revealed that the energy level of the radical-ion pair in toluene is located lower than that of the singlet and triplet states of the zinc porphyrin and fullerene entities. The femtosecond transient absorption measurements revealed fast charge sepn. from the singlet porphyrin to the coordinated C60Im with a lifetime of 1.1 ns. Interestingly, slow charge recombination (1.6 × 105 s-1) and the long lifetime of the charge-sepd. state (6.6 μs) were obtained in toluene by utilizing the nanosecond transient measurements.
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      (d) Menting, R.; Lau, J. T. F.; Xu, H.; Ng, D. K. P.; Röder, B.; Ermilov, E. A. Chem. Commun. 2012, 48, 4597– 4599 DOI: 10.1039/c2cc30286a
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
      (e) Managa, M.; Mack, J.; Gonzalez-Lucasb, D.; Remiro-Buenamañana, S.; Tshangana, C.; Cammidge, A. N.; Nyokong, T. J. Porphyrins Phthalocyanines 2016, 20, 1– 20 DOI: 10.1142/S1088424615500959
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    7. 7
      (a) González-Rodríguez, D.; Claessens, C. G.; Torres, T.; Liu, S.-G.; Echegoyen, L.; Vila, N.; Nonell, S. Chem. - Eur. J. 2005, 11, 3881– 3893 DOI: 10.1002/chem.200400779
      [Crossref], [PubMed], [CAS], Google Scholar
      7a
      Tuning photoinduced energy- and electron-transfer events in subphthalocyanine-phthalocyanine dyads
      Gonzalez-Rodriguez, David; Claessens, Christian G.; Torres, Tomas; Liu, Shenggao; Echegoyen, Luis; Vila, Nuria; Nonell, Santi
      Chemistry - A European Journal (2005), 11 (13), 3881-3893CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A series of subphthalocyanine-phthalocyanine dyads has been prepd. by palladium-catalyzed cross-coupling reactions between a monoalkynylphthalocyanine and different monoiodosubphthalocyanines. Electronic coupling between the two photoactive units is ensured by a rigid and π-conjugated alkynyl spacer. In addn., the electronic characteristics of the subphthalocyanine moiety were modulated by the introduction of different peripheral substituents. Cyclic and Osteryoung square-wave voltammetry expts. revealed that the redn. potential of this subunit can be decreased by about 400 mV on going from thioether or no substituents to nitro groups. As a consequence, the energy level of the charge-transfer state could be fine-tuned so as to gain control over the fate of the photoexcitation energy in each subunit. The diverse steady-state and time-resolved photophys. techniques employed demonstrated that, when the charge-transfer state lies high in energy, a quant. singlet-singlet energy-transfer mechanism from the excited subphthalocyanine to the phthalocyanine takes place. On the contrary, stabilization of the radical pair by lowering the redox gap between electron donor and acceptor results in a highly efficient photoinduced electron-transfer process, even in solvents of low polarity such as toluene (ΦET ≈ 0.9). These features, together with the extraordinary absorptive cross section that these mol. ensembles display across the whole UV/Vis spectrum, make them model candidates for application in situations where broadband light sources are needed.
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      (b) Zhao, Z.; Cammidge, A. N.; Cook, M. J. Chem. Commun. 2009, 7530– 7532 DOI: 10.1039/b916649a
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    8. 8
      (a) Cnops, K.; Rand, B. P.; Cheyns, D.; Verreet, B.; Empl, M. A.; Heremans, P. Nat. Commun. 2014, 5, 3406 DOI: 10.1038/ncomms4406
      [Crossref], [PubMed], [CAS], Google Scholar
      8a
      8.4% efficient fullerene-free organic solar cells exploiting long-range exciton energy transfer
      Cnops Kjell; Empl Max A; Heremans Paul; Rand Barry P; Cheyns David; Verreet Bregt
      Nature communications (2014), 5 (), 3406 ISSN:.
      In order to increase the power conversion efficiency of organic solar cells, their absorption spectrum should be broadened while maintaining efficient exciton harvesting. This requires the use of multiple complementary absorbers, usually incorporated in tandem cells or in cascaded exciton-dissociating heterojunctions. Here we present a simple three-layer architecture comprising two non-fullerene acceptors and a donor, in which an energy-relay cascade enables an efficient two-step exciton dissociation process. Excitons generated in the remote wide-bandgap acceptor are transferred by long-range Forster energy transfer to the smaller-bandgap acceptor, and subsequently dissociate at the donor interface. The photocurrent originates from all three complementary absorbing materials, resulting in a quantum efficiency above 75% between 400 and 720 nm. With an open-circuit voltage close to 1 V, this leads to a remarkable power conversion efficiency of 8.4%. These results confirm that multilayer cascade structures are a promising alternative to conventional donor-fullerene organic solar cells.
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      (b) Duan, C.; Zango, G.; García Iglesias, M.; Colberts, F. J. M.; Wienk, M. M.; Martínez-Díaz, M. V.; Janssen, R. A. J.; Torres, T. Angew. Chem., Int. Ed. 2017, 56, 148– 152 DOI: 10.1002/anie.201608644
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    9. 9
      Michinobu, T.; Boudon, C.; Gisselbrecht, J.-P.; Seiler, P.; Frank, B.; Moonen, N. N. P.; Gross, M.; Diederich, F. Chem. - Eur. J. 2006, 12, 1889– 1905 DOI: 10.1002/chem.200501113
      [Crossref], [PubMed], [CAS], Google Scholar
      9
      Donor-substituted 1,1,4,4-Tetracyanobutadienes (TCBDs). New chromophores with efficient intramolecular charge-transfer interactions by atom-economic synthesis
      Michinobu, Tsuyoshi; Boudon, Corinne; Gisselbrecht, Jean-Paul; Seiler, Paul; Frank, Brian; Moonen, Nicolle N. P.; Gross, Maurice; Diederich, Francois
      Chemistry - A European Journal (2006), 12 (7), 1889-1905CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A wide variety of monomeric and oligomeric, donor-substituted 1,1,4,4-tetracyanobutadienes (TCBDs) have been synthesized by [2+2] cycloaddn. between tetracyanoethylene (TNCE) and donor-substituted alkynes, followed by electrocyclic ring opening of the initially formed cyclobutenes. Reaction yields are often nearly quant. but can be affected by the electron-donating power and steric demands of the alkyne substituents. The intramol. charge-transfer (CT) interactions between the donor and TCBD acceptor moieties were comprehensively investigated by X-ray crystallog., electrochem., UV-visible spectroscopy, and theor. calcns. Despite the nonplanarity of the new chromophores, which have a substantial twist between the two dicyanovinyl planes, efficient intramol. CT interactions are obsd., and the crystal structures demonstrate a high quinoid character in strong donor substituents, such as N,N-dimethylanilino (DMA) rings. The maxima of the CT bands shift bathochromically upon redn. of the amt. of conjugative coupling between strong donor and acceptor moieties. Each TCBD moiety undergoes two reversible, one-electron redn. steps. Thus, a tri-TCBD deriv. with a 1,3,5-trisubstituted benzene core shows six reversible redn. steps within an exceptionally narrow potential range of 1.0 V. The first redn. potential Ered,1 is strongly influenced by the donor substitution: introduction of more donor moieties causes an increasingly twisted TCBD structure, a fact that results in the elevation of the LUMO level and, consequently, a more difficult first redn. The potentials are also strongly influenced by the nature of the donor residues and the extent of donor-acceptor coupling. A careful comparison of electrochem. data and the correlation with UV-visible spectra made it possible to est. unknown phys. parameters such as the Ered,1 of unsubstituted TCBD (-0.31 V vs. Fc+/Fc) as well as the maxima of highly broadened CT bands. Donor-substituted TCBDs are stable mols. and can be sublimed without decompn. With their high third-order optical non-linearities, as revealed in preliminary measurements, they should become interesting chromophores for ultra-thin film formation by vapor deposition techniques and have applications in opto-electronic devices.
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    10. 10
      (a) Tancini, F.; Monti, F.; Howes, K.; Belbakra, A.; Listorti, A.; Schweizer, W. B.; Reutenauer, P.; Alonso-Gómez, J.-L.; Chiorboli, C.; Urner, L. M.; Gisselbrecht, J.-P.; Boudon, C.; Armaroli, N.; Diederich, F. Chem. - Eur. J. 2014, 20, 202– 216 DOI: 10.1002/chem.201303284
      [Crossref], [PubMed], [CAS], Google Scholar
      10a
      Cyanobuta-1,3-dienes as novel electron acceptors for photoactive multicomponent systems
      Tancini, Francesca; Monti, Filippo; Howes, Kara; Belbakra, Abdelhalim; Listorti, Andrea; Schweizer, W. Bernd; Reutenauer, Philippe; Alonso-Gomez, Jose-Lorenzo; Chiorboli, Claudio; Urner, Lorenz M.; Gisselbrecht, Jean-Paul; Boudon, Corinne; Armaroli, Nicola; Diederich, Francois
      Chemistry - A European Journal (2014), 20 (1), 202-216CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The synthesis, electrochem., and photophys. properties of five multicomponent systems featuring a ZnII porphyrin (ZnP) linked to one or two anilino donor-substituted pentacyano- (PCBD) or tetracyanobuta-1,3-dienes (TCBD), with and without an interchromophoric bridging spacer (S), are reported: ZnP-S-PCBD (1), ZnP-S-TCBD (2), ZnP-TCBD (3), ZnP-(S-PCBD)2 (4), and ZnP-(S-TCBD)2 (5). By means of steady-state and time-resolved absorption and luminescence spectroscopy (RT and 77 K), photoinduced intramol. energy and electron transfer processes are evidenced, upon excitation of the porphyrin unit. In systems equipped with the strongest acceptor PCBD and the spacer (1, 4), no evidence of electron transfer is found in toluene, suggesting ZnP→PCBD energy transfer, followed by ultrafast (<10 ps) intrinsic deactivation of the PCBD moiety. In the analogous systems with the weaker acceptor TCBD (2, 5), photoinduced electron transfer occurs in benzonitrile, generating a charge-sepd. (CS) state lasting 2.3 μs. Such a long lifetime, in light of the high Gibbs free energy for charge recombination (ΔGCR=-1.39 eV), suggests a back-electron transfer process occurring in the so-called Marcus inverted region. Notably, in system 3 lacking the interchromophoric spacer, photoinduced charge sepn. followed by charge recombination occur within 20 ps. This is a consequence of the close vicinity of the donor-acceptor partners and of a virtually activationless electron transfer process. These results indicate that the strongly electron-accepting cyanobuta-1,3-dienes might become promising alternatives to quinone-, perylenediimide-, and fullerene-derived acceptors in multicomponent modules featuring photoinduced electron transfer.
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      (b) Koszelewski, D.; Nowak-Król, A.; Gryko, D. T. Chem. - Asian J. 2012, 7, 1887– 1894 DOI: 10.1002/asia.201200179
      [Crossref], [PubMed], [CAS], Google Scholar
      10b
      Selective Cycloaddition of Tetracyanoethene (TCNE) and 7,7,8,8-Tetracyano-p-quinodimethane (TCNQ) to Afford meso-Substituted Phenylethynyl Porphyrins
      Koszelewski, Dominik; Nowak-Krol, Agnieszka; Gryko, Daniel T.
      Chemistry - An Asian Journal (2012), 7 (8), 1887-1894, S1887/1-S1887/24CODEN: CAAJBI; ISSN:1861-4728. (Wiley-VCH Verlag GmbH & Co. KGaA)
      π-Extended TCBD-porphyrins that contains a 1,1,4,4-tetracyanobuta-1,3-diene unit were prepd. by a highly efficient [2+2] cycloaddn. of tetracyanoethene (TCNE) or 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) with meso-substituted trans-A2B2-porphyrins contg. two arylethynyl groups, followed by a retro-electrocyclization reaction. Depending on the electronic properties of the arylethynyl groups, the cycloaddn. reaction took place exclusively on either one or two ethynyl moieties with high yields. The addn. of TCNQ proceeded with complete regioselectivity. The resulting π-expanded TCBD-porphyrins had a hypsochromically shifted Soret band and showed unique, broad absorption in the visible region.
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    11. 11
      Wu, Y.-L.; Stuparu, M. C.; Boudon, C.; Gisselbrecht, J.-P.; Schweizer, W. B.; Baldridge, K. K.; Siegel, J. S.; Diederich, F. J. Org. Chem. 2012, 77, 11014– 11026 DOI: 10.1021/jo302217n
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      11
      Structural, Optical, and Electrochemical Properties of Three-Dimensional Push-Pull Corannulenes
      Wu, Yi-Lin; Stuparu, Mihaiela C.; Boudon, Corinne; Gisselbrecht, Jean-Paul; Schweizer, W. Bernd; Baldridge, Kim K.; Siegel, Jay S.; Diederich, Francois
      Journal of Organic Chemistry (2012), 77 (24), 11014-11026CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)
      Electrochem. active corannulene derivs. with various nos. of electron-donating 4-(N,N-dimethylamino)phenylethynyl (1-4) or electron-withdrawing cyanobutadienyl peripheral substituents (5-8) were prepd. The latter derivs. resulted from formal [2 + 2] cycloaddn. of cyanoolefins to 1-4 followed by retro-electrocyclization. Conformational properties were examd. by variable-temp. NMR and X-ray diffraction and opto-electronic properties by electronic absorption/emission spectra and electrochem. measurements; these analyses were corroborated by dispersion-cor. d. functional calcns. at the level of B97-D/def2-TZVPP. In CH2Cl2, 1-4 exhibit intramol. charge-transfer (ICT) absorptions at 350-550 nm and green (λem ∼ 540 nm) or orange (600 nm) fluorescence with high quantum yields (56-98%) and are more readily reduced than corannulene by up to 490 mV. The variation of optical gap and redox potentials of 1-4 does not correlate with the no. of substituents. Cyanobutadienyl corannulenes 5-8 show red-shifted ICT absorptions with end-absorptions approaching 800 nm. Intersubstituent interactions lead to distortions of the corannulene core and lower the mol. symmetry. NMR, X-ray, and computational studies on 5 and 8 with one cyanobutadienyl substituent suggested the formation of intermol. corannulene dimers. Bowl-inversion barriers around ΔG‡ = 10-11 kcal/mol were detd. for these two mols.
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    12. 12
      Sekita, M.; Ballesteros, B.; Diederich, F.; Guldi, D. M.; Bottari, G.; Torres, T. Angew. Chem., Int. Ed. 2016, 55, 5560– 5564 DOI: 10.1002/anie.201601258
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    13. 13

      See section 4 in the Supporting Information.

      There is no corresponding record for this reference.
    14. 14
      Camerel, F.; Ulrich, G.; Retailleau, P.; Ziessel, R. Angew. Chem., Int. Ed. 2008, 47, 8876– 8880 DOI: 10.1002/anie.200803131
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    15. 15

      CCDC 1532160 (racemate 1), 1532161 (enantiopure Sa-1), 1532162 (racemate 2), and 1532163 (enantiopure Ra-2) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre.

      There is no corresponding record for this reference.
    16. 16
      Morse, G. E.; Gong, I.; Kawar, Y.; Lough, A. J.; Bender, T. P. Cryst. Growth Des. 2014, 14, 2138– 2147 DOI: 10.1021/cg401475b
      [ACS Full Text ACS Full Text], [CAS], Google Scholar
      16
      Crystal and Solid-State Arrangement Trends of Halogenated Boron Subphthalocyanines
      Morse, Graham E.; Gong, Ivan; Kawar, Yazan; Lough, Alan J.; Bender, Timothy P.
      Crystal Growth & Design (2014), 14 (5), 2138-2147CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)
      A series of new crystal structures for the boron subphthalocyanine (BsubPc) derivs. chloro hexachloro BsubPc (Cl-Cl6BsubPc), chloro dodecachloro BsubPc (Cl-Cl12BsubPc), bromo/chloro hexachloro BsubPc (Br0.27|Cl0.73-Cl6BsubPc), bromo dodecachloro BsubPc (Br-Cl12BsubPc), and pentafluorophenoxy dodecachloro BsubPc (F5PhO-Cl12BsubPc) are reported. By combining these new crystal structures with a series of previously published structures into a comprehensive study, we have outlined several new structure crystal property/solid-state arrangement relationships for this expanded list of BsubPc derivs. Parameters that were examd. to establish the relationships include (a) geometric descriptors of the BsubPc mol. structure including the bowl shape of the BsubPcs; (b) molar d. of the crystals; and (c) void vol. fraction (Φ). Variations in the peripheral substituents (from hydrogen to fluorine and chlorine) were found to have a profound effect on the solid-state arrangement. No significant changes were noted when the axial substituent was varied from chlorine to bromine, whereas replacement of the axial halide with a pentafluorophenoxy fragment resulted in a notable change (as expected). It was also found that Cl-C12BsubPc (and its derivs.) had a high tendency to co-crystallize with solvents (form solvates), which resulted in a significantly different solid-state arrangement. We believe the observations detailed in this paper will lead to routes to engineer the crystn. of BsubPcs to facilitate tailored solid-state arrangement and properties.
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    17. 17

      A qualitative experiment addressing the stability of atropisomer Ra-2 towards racemization has been carried out (Figure S12.1). Further studies aiming at determining the energy barrier and activation parameters for the interconversion between the Sa and Ra atropisomers of 1 and 2 are currently in progress in our laboratories and will be reported in due course.

      There is no corresponding record for this reference.
    18. 18
      Yamada, M.; Rivera-Fuentes, P.; Schweizer, W. B.; Diederich, F. Angew. Chem., Int. Ed. 2010, 49, 3532– 3535 DOI: 10.1002/anie.200906853
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    19. 19
      Guilleme, J.; González-Rodríguez, D.; Torres, T. Angew. Chem., Int. Ed. 2011, 50, 3506– 3509 DOI: 10.1002/anie.201007240
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    20. 20
      Kato, S.; Diederich, F. Chem. Commun. 2010, 46, 1994– 2006 DOI: 10.1039/b926601a
      [Crossref], [PubMed], [CAS], Google Scholar
      20
      Non-planar push-pull chromophores
      Kato, Shin-ichiro; Diederich, Francois
      Chemical Communications (Cambridge, United Kingdom) (2010), 46 (12), 1994-2006CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      A review. The development of a unique class of non-planar push-pull chromophores by means of [2+2] cycloaddn., followed by cycloreversion, of electron-deficient olefins, such as tetracyanoethene (TCNE), 7,7,8,8-tetracyanoquinodimethane (TCNQ) and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), as well as dicyanovinyl (DCV) and tricyanovinyl (TCV) derivs., to donor-substituted alkynes is explored in this feature article. This high-yielding, "click-chem."-type transformation with acetylenic dendrimers affords dendritic electron sinks capable of multiple electron uptake within a narrow potential range. An [AB]-type oligomer with a dendralene backbone was synthesized by a one-pot, multi-component cascade reaction of polyyne oligomers with TCNE and tetrathiafulvalene (TTF). In most cases, the resulting chromophores feature intense intramol. charge-transfer bands extending far into the near IR region and some of them display high third-order optical nonlinearities. Despite substitution with strong donors, the electron-withdrawing moieties in the new chromophores remain potent acceptors and a no. of them display pos. first redn. potentials (vs. the ferrocenium/ferrocene (Fc+/Fc) couple in CH2Cl2), which rival those of parent TCNE, TCNQ and F4-TCNQ. The non-planarity of the chromophores strongly enhances their phys. properties when compared to planar push-pull analogs. They feature high soly., thermal stability and sublimability, which enables formation of amorphous, high-optical-quality thin films by vapor phase deposition and makes them interesting as advanced functional materials for novel opto-electronic devices.
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    21. 21
      Kimura, K.; Tsubomura, H.; Nagakura, S. Bull. Chem. Soc. Jpn. 1964, 37, 1336– 1346 DOI: 10.1246/bcsj.37.1336
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    22. 22

      Singlet excited-state energies of SubPc were calculated as an average value by means of the following eq:where λmax(abs) is the absorption maximum at the longest wavelength and λmax(em) is the fluorescence maximum at the shortest wavelength.

      There is no corresponding record for this reference.
    23. 23

      Please note that such differences between the excitation and the absorption spectra are not observed in the case of SubPc–ethynyl–aniline conjugates 3 and 4 (Figure S10.8).

      There is no corresponding record for this reference.
    24. 24
      (a) Gordon, M.; Ware, W. R., Eds. The Exciplex; Academic Press: New York, 1975.
      Google Scholar
      There is no corresponding record for this reference.
      (b) Verhoeven, J. W. Pure Appl. Chem. 1996, 68, 2223– 2286 DOI: 10.1351/pac199668122223
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    25. 25
      It is important to notice that the formation of an excited dimer species (i.e., an excimer) through excited-state interactions between two identical molecular entities of 2 can be excluded here. Excimer fluorescence is concentration-dependent, whereas in the case of 2 the broad, featureless fluorescence is already observed at concentrations less than 10–6 M (Figure S10.11). In addition, usually, the maximum of the excimer fluorescence is only weakly solvent-dependent (Turro, N. J.; Ramamurthy, V.; Scaiano, J. C. Modern Molecular Photochemistry of Organic Molecules; University Science Books: Sausalito, CA, 2010; pp 1– 1110), whereas in the case of 2, a strong solvent polarity effect is noticed. Based on these findings, and considering that SubPcs are not susceptible to aggregation in solution, an intermolecular excited dimer formation is unfeasible.
      Google Scholar
      There is no corresponding record for this reference.
    26. 26
      Aydemir, M.; Jankus, V.; Dias, F. B.; Monkman, A. P. J. Phys. Chem. C 2015, 119, 5855– 5863 DOI: 10.1021/jp512467g
      [ACS Full Text ACS Full Text], Google Scholar
      There is no corresponding record for this reference.
    27. 27
      Radiative Decay Engineering; Lakowicz, J. R.; Geddes, C. D., Eds.; Springer: New York, 2005.
      Google Scholar
      There is no corresponding record for this reference.
    28. 28

      It is important to consider that little, or no, electronic communication between the two DCV units of the TCBD moiety in 1, 2, and 7 is expected to occur in the ground state because the two DCVs are placed in an almost perpendicular arrangement, as inferred by X-ray crystal structure determination.

      There is no corresponding record for this reference.
    29. 29

      ΦΔ values were determined with respect to F12SubPc reference compound 8, which has a ΦΔ of 0.31 in toluene.

      There is no corresponding record for this reference.
    30. 30
      Feng, L.; Rudolf, M.; Trukhina, O.; Slanina, Z.; Uhlik, F.; Lu, X.; Torres, T.; Guldi, D. M.; Akasaka, T. Chem. Commun. 2015, 51, 330– 333 DOI: 10.1039/C4CC08072F
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
    31. 31
      Rudolf, M.; Trukhina, O.; Perles, J.; Feng, L.; Akasaka, T.; Torres, T.; Guldi, D. M. Chem. Sci. 2015, 6, 4141– 4147 DOI: 10.1039/C5SC00223K
      [Crossref], [PubMed], [CAS], Google Scholar
      31
      Taming C60 fullerene: tuning intramolecular photoinduced electron transfer process with subphthalocyanines
      Rudolf, Marc; Trukhina, Olga; Perles, Josefina; Feng, Lai; Akasaka, Takeshi; Torres, Tomas; Guldi, Dirk M.
      Chemical Science (2015), 6 (7), 4141-4147CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
      Two subphthalocyanine-C60 conjugates have been prepd. by means of the 1,3-dipolar cycloaddn. reaction of (perfluoro) or hexa(pentylsulfonyl) electron deficient subphthalocyanines to C60. Comprehensive assays regarding the electronic features - in the ground and excited state - of the resulting conjugates revealed energy and electron transfer processes upon photoexcitation. Most important is the unambiguous evidence - in terms of time-resolved spectroscopy - of an ultrafast oxidative electron transfer evolving from C60 to the photoexcited subphthalocyanines. This is, to the best of our knowledge, the first case of an intramol. oxidn. of C60 within electron donor-acceptor conjugates by means of only photoexcitation.
      >> More from SciFinder ®
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    32. 32

      Please note that the electrochemistry in nonaqueous media such as o-DCB may be influenced by protonation/deprotonation occurring upon the initial redox process:

      Xue, S.; Ou, Z.; Ye, L.; Lu, G.; Fang, Y.; Jiang, X.; Kadish, K. M. Chem. - Eur. J. 2015, 21, 2651– 2661 DOI: 10.1002/chem.201405570
      [Crossref], [PubMed], [CAS], Google Scholar
      32
      Effect of Solvent and Protonation/Deprotonation on Electrochemistry, Spectroelectrochemistry and Electron-Transfer Mechanisms of N-Confused Tetraarylporphyrins in Nonaqueous Media
      Xue, Songlin; Ou, Zhongping; Ye, Lina; Lu, Guifen; Fang, Yuanyuan; Jiang, Xiaoqin; Kadish, Karl M.
      Chemistry - A European Journal (2015), 21 (6), 2651-2661CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A series of N-confused free-base meso-substituted tetraarylporphyrins was investigated by electrochem. and spectroelectrochem. in nonaq. media contg. 0.1 M tetra-n-butylammonium perchlorate (TBAP) and added acid or base. The investigated compds. were represented as (XPh)4NcpH2, in which "Ncp" is the N-confused porphyrin macrocycle and X is a OCH3, CH3, H, or Cl substituent on the para position of each meso-Ph ring of the macrocycle. Two distinct types of UV/Vis spectra were initially obsd. depending upon solvent, one corresponding to an inner-2H form and the other to an inner-3H form of the porphyrin. Both forms have an inverted pyrrole with a carbon inside the cavity and a nitrogen on the periphery of the π-system. Each porphyrin undergoes multiple irreversible redns. and oxidns. The first one-electron addn. and first one-electron abstraction are located on the porphyrin π-ring system to give π-anion and π-cation radicals with a potential sepn. of 1.52 to 1.65 V between the two processes, but both electrogenerated products are unstable and undergo a rapid chem. reaction to give new electroactive species, which were characterized in the present study. The effect of the solvent and protonation/deprotonation reactions on the UV/Vis spectra, redox potentials and redn./oxidn. mechanisms is discussed with comparisons made to data and mechanisms for the structurally related free-base corroles and porphyrins.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXitFaiurzJ&md5=7716b4d7db60d393887a639369a09397

      In case of 6, the F12SubPc•– radical anion initially formed upon electrochemical reduction is probably unstable on the spectroelectrochemical time scale evolving toward a deprotonated/protonated species as a byproduct of the electrochemical reduction. Therefore, the spectroelectrochemical features of 6•– are blurred and do not resemble the clear and sharp transient absorption features of the F12SubPc•– radical anion.

    33. 33
      (a) Sosorev, A. Y.; Paraschuk, D. Y. Isr. J. Chem. 2014, 54, 650– 673 DOI: 10.1002/ijch.201400063
      [Crossref], [CAS], Google Scholar
      33a
      Charge-Transfer Complexes of Conjugated Polymers
      Sosorev, Andrey Yu.; Paraschuk, Dmitry Yu.
      Israel Journal of Chemistry (2014), 54 (5-6), 650-673CODEN: ISJCAT; ISSN:0021-2148. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A review. Donor-acceptor blends of conjugated polymers (CPs) are workhorse materials for the state-of-the-art polymer solar cells. Although earlier it was suggested that charge transfer in these blends occurred only in the excited electronic state, a body of evidence for ground-state charge transfer and the corresponding charge-transfer complex (CTC) formation has been reported in the last decade. In some CP:acceptor blends, the CTC is pronounced and can be noticed visually as a color change, while in more common CP:fullerene blends it is very weak. However, in both, the CTC governs charge sepn., which is the key photophys. process for org. solar cells, through so-called charge-transfer states. Moreover, the pronounced CTC can substantially modify the blend properties: extend the blend absorption in the red and IR regions, change the morphol. to facilitate donor-acceptor intermixing, stimulate polymer self-organization and ordering, and increase the polymer photooxidn. stability. Addn. of one of the strongest org. acceptors, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), to the CP:fullerene blend is an example of org. doping (a CTC with full charge transfer), improving the blend structural and electronic properties and finally the solar cell performance. In this review, we summarize the current knowledge on CTCs in various CP:acceptor blends and the impact of CTC on the blend properties and the device performance.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXps1ymurs%253D&md5=c066ffe11be78e4b920434dbfe671d1a
      (b) Deibel, C.; Strobel, T.; Dyakonov, V. Adv. Mater. 2010, 22, 4097– 4111 DOI: 10.1002/adma.201000376
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
      (c) Akaike, K.; Kanai, K.; Ouchi, Y.; Seki, K. Adv. Funct. Mater. 2010, 20, 715– 721 DOI: 10.1002/adfm.200901585
      [Crossref], Google Scholar
      There is no corresponding record for this reference.
      (d) Benson-Smith, J. J.; Goris, L.; Vandewal, K.; Haenen, K.; Manca, J. V.; Vanderzande, D.; Bradley, D. D. C.; Nelson, J. Adv. Funct. Mater. 2007, 17, 451– 457 DOI: 10.1002/adfm.200600484
      [Crossref], Google Scholar
      There is no corresponding record for this reference.

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