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Planar and Curved π-Extended Porphyrins by On-Surface Cyclodehydrogenation
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Journal of the American Chemical Society

Cite this: J. Am. Chem. Soc. 2024, 146, 50, 34600–34608
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https://doi.org/10.1021/jacs.4c12460
Published December 4, 2024

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Abstract

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Recent advancements in on-surface synthesis have enabled the reliable and predictable preparation of atomically precise low-dimensional materials with remarkable properties, which are often unattainable through traditional wet chemistry. Among these materials, porphyrins stand out as a particularly intriguing class of molecules, extensively studied both in solution and on surfaces. Their appeal lies in the ability to fine-tune their unique chemical and physical properties through central metal exchange or peripheral functionalization. However, the synthesis of π-extended porphyrins featuring unsubstituted anthracenyl groups has remained elusive. Herein, we report an in vacuo temperature-controlled cyclodehydrogenation of bis- and tetraanthracenyl Zn(II) porphyrins on a gold(111) surface. By gradually increasing the temperature, sequential dehydrogenation leads to the formation of fused anthracenyl porphyrin products. Notably, at high molecular coverage, the formation of bowl-shaped porphyrins occurs, along with transmetalation of Zn with Au. These findings open the door to a variety of π-extended anthracenyl-containing porphyrin products via cyclodehydrogenation and transmetalation, offering significant potential in the fields of molecular (photo/electro)catalysis, (opto)electronics, and spintronics.

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Introduction

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Porphyrins are tetrapyrrolic aromatic macrocycles with pyrrolic moieties connected via four methinebridges. The cavity of the macrocycle has the ability to host metals, and metalated porphyrins are building blocks of natural systems such as heme and chlorophyll, playing a paramount biological role in oxygen transport, light harvesting, and numerous redox processes. (1,2) Synthetic analogues of naturally occurring macrocycles have been the focus of a vast number of research areas spanning from biological model systems to components of electronic, spintronic, optoelectronic, and photovoltaic devices. (3−10) Another important aspect of research on porphyrins concerns the investigation of their chemical and physical properties on surfaces. (11−20) Moreover, for metalated macrocycles in a curved aromatic sheet, exceptional electrocatalytic properties for water splitting are expected. (21)
The chemical and physical properties of porphyrins can be precisely controlled through central metal modification or peripheral functionalization. (22−25) The latter, in particular, has been shown to depend heavily on both the number and nature of peripheral functional groups, which are crucial for fine-tuning these properties. (23,25,26) Especially noteworthy is functionalization that involves oxidative coupling (fusion) of polycyclic aromatic hydrocarbons attached in the meso position of porphyrin to the β positions of the pyrrolic subunits. Such process expands the aromatic system, thereby significantly improving the optical properties of the porphyrin. (26−38)
Among the polyaromatic hydrocarbons to be fused to porphyrins, anthracene stands out as particularly elegant when attached at the meso position. The C1 and C8 carbon atoms of anthracene can form two new C–C bonds with the β-pyrrolic carbon atoms of porphyrin, creating a highly integrated and structurally refined system.
About a decade ago, Anderson and co-workers reported the synthesis of fused bis- and tetraanthracenyl Ni(II) porphyrins, showcasing remarkable shifts in absorbance maxima upon fusion (Scheme 1a). (27,28) However, the formation of π-extended porphyrins bearing unsubstituted anthracenyl moieties or overoxidized anthracenyl porphyrin derivatives has yet to be achieved. Herein, we demonstrate the formation of such compounds by an on-surface synthesis method (Scheme 1b). On-surface synthesis has recently become a leading technique for controllable C–C bond formation that would otherwise hardly be accessible by conventional solution chemistry. It enables the reliable and predictable preparation of atomically precise low-dimensional materials with unprecedented properties, identified and characterized primarily through scanning probe techniques. (39−47)

Scheme 1

Scheme 1. Comparison of Solution and On-Surface Synthesis of Fused Anthracenyl Porphyrins
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The temperature-controlled synthesis of fused Zn bis- and tetraanthracen-9-yl porphyrins (ZnBAP and ZnTAP) proceeds by cyclodehydrogenation of the corresponding meso-substituted porphyrins on the Au(111) surface. Notably, on-surface dehydrogenation is not limited to the first dehydrogenation step involving the fusion of anthracenyl units to the macrocycle. Sequential dehydrogenation with temperature elevation leads to new products, as identified by scanning tunneling microscopy (STM), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and X-ray photoemission spectroscopy (XPS).

Results and Discussion

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Synthesis of Porphyrin Derivatives

ZnBAP and ZnTAP were synthesized according to procedures derived from the literature (48,49) (see the Experimental Section and Supporting Information for details).

ToF-SIMS Analysis of Surface Reaction Products

After deposition of ZnBAP and ZnTAP onto the clean Au(111) surface, stepwise annealing led to fused anthracenyl porphyrins. The results are summarized in Figure 1.

Figure 1

Figure 1. ToF-SIM spectra tracking mass loss due to cyclodehydrogenation of Zn-anthracenyl porphyrins upon thermal activation. (a) Temperature series of ZnBAP on Au(111) leading to ZnBAP-8H and ZnBAP-12H products upon annealing to 458 and 603 K, respectively. Colored bars above the spectra represent expected mass distributions of C60H36N4Zn+ (ZnBAP), C60H28N4Zn+ (ZnBAP-8H), and C60H24N4Zn+ (ZnBAP-12H) ions. (b) ToF-SIMS temperature series of ZnTAP on Au(111) showing masses corresponding to ZnTAP, ZnTAP-16H, and ZnTAP-20H. Simulated mass distributions thereof are shown in the spectra.

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Upon deposition, ZnBAP is identified by the signal appearing from 876.2 to 884.2 amu with its characteristic isotopic pattern that corresponds to the C60H36N4Zn+ (ZnBAP+) ion. Upon annealing to 458 K, the signal shifts by 8 amu downward, corresponding to the loss of 8 H atoms and formation of 4 single C–C bonds (ZnBAP-8H). This loss is ascribed to the on-surface cyclodehydrogenation-induced fusion of both anthracenyl units at the β-pyrrolic carbon positions of porphyrin (Scheme 1b, left). The fusion of two anthracenyl units occurs at a temperature that is significantly lower than the temperature needed for cyclodehydrogenation of bisanthracene oligomers or bisanthracene–porphyrin hybrids, (50−52) however, well in line with the temperature required for cyclodehydrogenation of 5,15-bis(10-bromoanthracen-9-yl)-10,20-bis(trifluoromethyl)porphyrins on Au(111). (53) The reason for the reduction here is likely due to the improved mobility of gold adatoms and their better access to the reaction centers due to the absence of halogens on the surface as well as amenable molecular conformation. Gold adatoms have lately been identified as catalysts for on-surface (cyclo)dehydrogenation. (54−58) Further annealing to 603 K leads to the additional signal shift by 4 amu due to fusion of the phenyl groups of the ZnBAP-8H molecule. The fusion can lead to both anti- and syn- ZnBAP-12H species, as indicated in Scheme 1b, left. Notably, such products were not observed in the previous work, namely, the solution-based synthesis. (28)
ZnTAP molecules are identified in ToF-SIMS (Figure 1b) by their characteristic mass signals appearing from 1076.3 to 1086.3 amu. At 433 K, a 16 amu shift toward lower mass is observed, indicating a loss of 16 H atoms (ZnTAP-16H). Such loss corresponds to the formation of 8 C–C single bonds due to fusion of all four anthracenyl units to the porphyrin macrocycle (Scheme 1b, right). This temperature is almost identical to the temperature when anthracenyl units fuse to the macrocycle in the case of ZnBAP. A further loss of an additional 4 amu at 593 K suggests the formation of additional C–C bonds between adjacent anthracenyl units (ZnTAP-20H, Scheme 1b, right). Note that this product was also not observed in solution-based work. (27) Annealing above 593 K leads to intermolecular coupling/polymerization as well as transmetalation with Au (vide infra), thus inducing the loss of specific signals in ToF-SIMS.

STM of Surface Products

STM experiments performed on ZnBAP and ZnTAP molecules on the Au(111) substrate are summarized in Figures 2 and 3, respectively. Larger-scale overview images are shown in the Supporting Information.

Figure 2

Figure 2. STM identification of native and cyclodehydrogenated ZnBAP molecular species. (a) Overview STM image (25 × 25 nm2) of native ZnBAP molecules on Au(111) assembled into braid-like structures. (b) Close-up STM image (5 × 5 nm2) from (a) overlaid with ball-and-stick molecular models. (c) Simulated unoccupied state density maps of ZnBAP molecules as arranged in (b). (d) Overview STM image (30 × 30 nm2) of ZnBAP-8H molecules on Au(111) obtained after being annealed to 468 K. (e) Close-up STM image (5 × 5 nm2) of three ZnBAP-8H molecules overlaid with molecular models. (f) Simulated occupied state density maps of ZnBAP-8H molecules from (e). (g) Overview STM image (30 × 30 nm2) of ZnBAP-12H molecules on Au(111) obtained after annealing to 603 K. The molecules encircled in blue appear much brighter due to transmetalation of Zn with Au. (h) Close-up STM image (5 × 5 nm2) of two ZnBAP-12H molecules overlaid with the molecular models. (i) Simulated occupied state density maps of anti- and syn-ZnBAP-12H molecules from (h).

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Figure 3

Figure 3. STM identification of native and cyclodehydrogenated ZnTAP molecular species. (a) Overview STM image (15 × 15 nm2) of native ZnTAP molecules self-assembled on Au(111). The image is superimposed with ball-and-stick molecular models. (b) Ball-and-stick molecular model of the molecular assembly from (a), together with simulated unoccupied state density maps of ZnTAP molecules as arranged in the model. (c) Overview STM image (30 × 30 nm2) of ZnTAP-16H molecules imaged after annealing to 483 K. Molecules are encircled depending on the conformation with the color code from (d). Gray encircled molecules appear as if they are missing one anthracenyl unit, an impurity from the synthesis or fragmentation during the sublimation. (d) Simulated occupied state density maps of six possible conformations of ZnTAP-16H molecules. The labeling of the conformers is performed starting from the upper left corner. (e) Overview STM image (20 × 20 nm2) of ZnTAP-20H molecules imaged after annealing to 613 K. The inset represents simulated unoccupied state density map of an adatom-coordinated structure. (f) Overview (50 × 50 nm2) and (g, h) close-up (15 × 15 nm2) STM images obtained after annealing to 653 K. ZnTAP-20H molecules form different size oligomers via intermolecular C–C coupling. (i) Overview STM image (50 × 33.2 nm2) of a sample with very high molecular coverage obtained after annealing to 653 K with molecules appearing as up/down bowls. (j) Simulated unoccupied state density maps of ZnTAP-24H molecules appearing as up/down bowls and ZnTAP-22H molecules with the Au adatom.

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Upon deposition onto a clean Au(111) substrate, ZnBAP molecules arrange into interwoven structures, as depicted in Figure 2a. In the lower left corner of the image, an island exhibiting low contrast is observed from the assembled impurities, most likely the leftover solvents from the synthesis. The close-up image shown in Figure 2b is overlaid with ball-and-stick molecular models obtained from force-field molecular modeling. Extended Hückel simulated unoccupied state density maps of such arranged molecules are shown in Figure 2c. The molecules in the middle of the interwoven structure form a linear chain through overlapping phenyl rings; the molecules on the outer edge assemble around them through the interaction of anthracenyl units.
The STM image shown in Figure 2d was obtained after annealing to 468 K, a temperature where loss of 8 H atoms occurs. ZnBAP-8H molecules were imaged as flat rectangles with bright protrusions at the middle of the long edge. Such a shape is consistent with the fusion of anthracenyl units to the porphyrin macrocycle, with phenyl rings appearing as protrusions. This is evident in the close-up image in Figure 2e that is superimposed with the molecular structures as well as in the simulated occupied state density maps shown in Figure 2f. Molecules assemble mostly onto the fcc facet of Au(111) along the herringbone reconstruction in the form of a chain. The assembly is promoted via interaction with the adjacent phenyl groups. Some molecules appear to be further dehydrogenated and resemble ZnBAP-12H (see below).
After annealing to 603 K and fusion of the phenyl groups to the macrocycle, ZnBAP-12H molecules were imaged completely flat (Figure 2g). Molecules are assembled randomly due to the absence of phenyl–phenyl interactions. The preference for the fcc facet of the herringbone reconstruction is still maintained. The molecules encircled in blue appear much brighter in the center due to Zn transmetalation with Au. Porphyrin metalation with Au adatoms has been shown to occur at similar temperatures. (54,59,60) Some molecules appear to be missing one anthracenyl unit, most likely an impurity remaining from synthesis, products of fragmentation during sublimation, or side product of a surface reaction.
Both anti- and syn- ZnBAP-12H species are observed (Figure 2g,h,i). On the account of three different images shown in Figure S1 in the Supporting Information, there is a prevalence for the formation of anti- ZnBAP-12H with a yield of 70 ± 5% (Table S1 in the Supporting Information). This is well in accordance with previous work involving cyclodehydrogenation of metalated porphyrin molecules. (20) Interestingly, for the molecules that are missing one anthracenyl unit (Zn-mono anthracenyl porphyrin, ZnMAP) the preference turns toward the syn- species with a yield of 59 ± 4% (Table S1 in the Supporting Information). There can be numerous reasons for such behavior reflected in the electronic structure of the ZnMAP molecule and the intermediate dehydrogenation products; however, detailed investigation thereof is beyond the scope of this manuscript.
Ordered islands of ZnTAP molecules are observed upon deposition on the Au(111) substrate (Figure 3a). Molecules adsorb ’parallel’ to the surface in a pinwheel configuration. A comparison of different adsorption geometries of ZnTAP is shown in Figure S2 and is accompanied by the simulated state density maps thereof. As evident from Figure S2, the pinwheel adsorption geometry provides the best building block for the observed molecular self-assembly. This is in contrast to the tetra-bromoanthracenyl-porphyrin row-like self-assembly on silver surfaces where edge-on adsorption geometry is observed. (61) Self-assembly of ZnTAP is facilitated via the overlap of the anthracenyl units of neighboring molecules, similar to the case of ZnBAP molecules. The protruding anthracenyl units of four neighboring molecules are held together and appear bright in the image. Dark regions between them represent porphyrin macrocycles, as deducted from the edge of the molecular island. This is further corroborated via simulated unoccupied state density maps of ZnTAP molecules as arranged in the proposed model (Figure 3b).
Following annealing to 483 K and fusion of the anthracenyl units to the porphyrin macrocycle, ZnTAP-16H molecules are imaged as mostly flat with four pronounced protrusions (Figure 3c). The protrusions arise as a consequence of sterical overcrowding between the adjacent anthracenyl units and surface confinement. Six conformations are derived from the possibility to form M- or P- pentahelicene units in each of the four sites where anthracenyl units meet. Simulated occupied state density maps of those conformations are shown in Figure 3d. Labeling of the conformers is performed starting from the upper left corner, and the color code is used in Figure 3c as well as in Figure S3. Homochiral (MMMM and PPPP) conformers are the most abundant, while all of the other conformers could be identified in Figures 3c or S3. Their abundance is summarized in Table S2. Gray encircled molecules appear as if they are missing one anthracenyl unit, again an impurity from the synthesis or possibly a consequence of fragmentation during the sublimation or surface reaction.
Annealing to 613 K led to the formation of two additional C–C bonds between the adjacent anthracenyl units. The bonds form exclusively on the opposite sides of the ZnTAP-20H molecule (Figure 3e). The other two sides appear in the STM as a rather flat gap. Molecular modeling suggests that dehydrogenation might as well occur at these positions, but instead of the C–C bond formation, coordination with Au adatoms takes place. The inset within Figure 3e represents the simulated unoccupied state density map of such structure. A comparison of simulated images of several structures, namely, non-, partly, or fully dehydrogenated, as well as surface- and adatom-coordinated, is shown in Figure S4. The best match with the experimentally observed appearance is obtained in the case of dehydrogenation and Au adatom coordination (Figure S4e).
Further temperature increase and annealing to 653 K led to the polymerization of ZnTAP-20H molecules via intermolecular C–C coupling. Different sizes of oligomers were formed, as visible in Figure 3f. The coupling occurs next to the gap sides of the molecules (Figure 3g,h). This is in line with the previous assumption that dehydrogenation occurred at the two “gap” sides of the molecule, and the formed radicals were stabilized by adatom coordination. Similar behavior is observed in the case of open-shell [5]-rhombene molecule annealed on the Au(111) substrate. (62)
Interestingly, distinct situation occurs when a sample with very high molecular coverage, i.e., a full layer of ZnTAP-16H, was annealed to 653 K. Namely, molecules are here imaged either as circles with a darker region in the middle, or as bright circles with fading intensity from the middle outward (Figures 3i and S5). Such appearances are congruent with bowl-like molecular structures of ZnTAP-24H molecules adsorbed in bowl up/down configurations (Figure 3j). The up/down arrangement of adjacent bowls is expected to maximize the intermolecular π–π interaction and has been observed previously for C38 buckybowls on Cu(111). (63) We have modeled the appearance of several different structures, namely, the adsorption of atomic and molecular hydrogen onto ZnTAP-20H molecules, transmetalation with Au or Zn demetalation. However, good agreement with the STM appearance is achieved only if indeed all four C–C bonds between the adjacent anthracenyl units in ZnTAP-16H are formed (Figure S6). Note that transmetalation of ZnTAP-24H molecules with Au cannot be completely excluded due to a similarity in the simulated state density maps in Figure S6. The formation of ZnTAP-24H molecules might at first be surprising, but there are examples in surface chemistry where coverage plays an important role in steering the surface chemistry. (41,64−66) Moreover, already at the low coverage, there are indications that dehydrogenation occurs at all four sterically overcrowded centers of ZnTAP-16H molecules, in two of them, new C–C bonds were formed, while the other two were stabilized with surface adatoms. The stabilization of these molecular ends with adatoms would become difficult at very high coverages due to a limited availability as well as accessibility for Au adatoms. Additionally, lateral repulsion and compression of the molecular layer would push the molecules toward the formation of additional intramolecular C–C bonds. Notably, this does not preclude the formation of intermolecular C–C bonds but is probably a competing process. Occasionally, a bright protrusion at the molecular rim is observed. The protrusion could be interpreted as a formation of 3 out of 4 C–C bonds in the ZnTAP-16H molecule (ZnTAP-22H molecule with Au adatoms). The simulated state density maps thereof are shown in Figure 3j (right) and Figure S6g, corroborating such interpretation.
At intermediate molecular coverage, namely with 65% of ZnTAP-16H molecules (Figure S7a–c), annealing to 603 K already led to the intermolecular coupling, i.e., polymerization (Figure S7d–f). This temperature is lower than the temperature that was required to induce polymerization at the low coverage (∼17%) sample shown in Figure 3c,e,f. Such behavior is not surprising since higher coverage would increase the probability that two ZnTAP-20H molecules meet and form an intermolecular bond. A similar trend is observed in the ToF-SIMS temperature series of samples with higher molecular coverage, as shown in Figure S8a. Importantly, the presence of ZnTAP-20H signals is not observed here with an elevation in temperature. Instead, molecular dimers thereof appear upon annealing to 518 K (Figure S8b). Upon further annealing, specific signals disappear again due to the formation of larger oligomers and transmetalation.

Transmetalation of Zn with Au

Species with very bright protrusion in the middle of the molecule, i.e., in the porphyrin macrocycle, were also observed in the STM experiments. These were ascribed to the Au-containing porphyrins due to transmetalation. In order to shed light on the transmetalation process, XPS was employed. Temperature-dependent Zn 2p and N 1s XP spectra of ZnBAP and ZnTAP molecules are shown in Figure 4a,b, respectively.

Figure 4

Figure 4. Temperature-dependent Zn 2p and N 1s XP spectra of ZnBAP/ZnTAP on Au(111). (a) Zn 2p and N 1s XP spectra obtained upon deposition and annealing of ZnBAP molecules on the Au(111) substrate. (b) Zn 2p and N 1s XP spectra obtained upon deposition and annealing of ZnTAP molecules on the Au(111) substrate. Significant reduction of all XPS signals was observed at the first annealing step due to molecular desorption. Additional molecular deposition was therefore performed while keeping the substrate at 473 K.

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For both molecules, Zn 2p3/2 peaks appear at a binding energy of 1021.2 ± 0.2 eV. N 1s peaks appear at the binding energy of 397.9 ± 0.2 eV, exhibiting a single component. This is in very good agreement with XPS studies of other Zn-porphyrins adsorbed on Au(111). (67,68) Upon annealing, Zn 2p signals gradually reduce and disappear at 773 K. During the Zn 2p signal reduction, almost no change is observed in the N 1s signals, neither in the intensity nor in the N 1s peak binding energy. This suggests that the Zn 2p signal decrease is due to demetalation and removal of Zn from the substrate via desorption or diffusion into the substrate and not to molecular desorption. Concurrently, metalation with Au occurs. The absence of higher-binding energy aminic N 1s feature at any annealing step suggests that the Zn demetalation and Au metalation occurred simultaneously, in a so-called transmetalation/atom-exchange process. Transmetalation of porphyrins and pyrphyrins on surfaces has been reported earlier, (69−71) however, to the best of our knowledge not with Au. Note that significant reduction of all XPS signals was observed at the first annealing step of ZnTAP molecules due to molecular desorption; in order to circumvent that, additional molecular deposition was performed while keeping the substrate at 473 K. The Au transmetalation is also evident in AuTAP, AuTAP-16H, and AuTAP-20H ToF-SIMS signals shown in Figure S8c,d, in particular at elevated temperatures when the originating signals of ZnTAP vanish.

Conclusions

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In summary, an in-depth study of the on-surface synthesis of fused Zn bis- and tetraanthracen-9-yl porphyrins (ZnBAP and ZnTAP) by cyclodehydrogenation of the corresponding meso-substituted porphyrins on the Au(111) surface is provided herein. Starting from ZnBAP and ZnTAP, sequential dehydrogenation with temperature elevation leads to novel π-extended products beyond the ones obtained by wet synthesis. The products were identified in a combined STM, ToF-SIMS, and XPS study and are accompanied by molecular modeling. In the case of ZnBAP molecule, two cyclodehydrogenation steps are observed; in the first step, anthracenyl units fuse to the macrocycle (ZnBAP-8H). In the second step, phenyl groups fuse to the macrocycle in both anti- and syn-configurations (ZnBAP-12H). In the case of ZnTAP molecule, first the anthracenyl units fuse to the porphyrin macrocycle leading to the π-extended Zn porphyrin–helicene hybrid (ZnTAP-16H). The products of further annealing depend on the molecular coverage. At low coverage, two additional bonds are formed (ZnTAP-20H) and lead to molecular polymerization with temperature increase. At high coverage, three to four additional bonds form and lead to the formation of bowl-shaped porphyrin products (ZnTAP-22H and ZnTAP-24H). The overview of the observed surface products is summarized in Figure S9. In addition, the cyclodehydrogenation process is accompanied by the transmetalation of Zn with Au. The particular results demonstrate a facile strategy for the access to numerous anthracenyl-based π-extended porphyrin products that are of interest in the fields of molecular (photo/electro)catalysis, (opto)electronics, and spintronics via cyclodehydrogenation and transmetalation.

Experimental Section

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Anthracenyl Porphyrin Synthesis

ZnBAP and ZnTAP molecules were synthesized according to Scheme S1, and the full details about the synthesis and product characterization are provided in the Supporting Information. In short, ZnBAP was synthesized in four steps from 5,15-diphenylporphyrin: Zn metal incorporation, iodination at the meso position accompanied by demetalation, attachment of anthracenyl units, and finally metalation with Zn. (48) ZnTAP was synthesized according to the method developed by Volz and Schäffer. (49) Briefly, 9-bromoanthracene was treated with n-butyl lithium which reacted with pyrrole-2-carboxaldehyde. The carbinol intermediate was tetramerized to give tetra-anthracenyl porphyrin. Finally, it was metalated with Zn.

Sample Preparation

All experiments were performed under ultrahigh vacuum (UHV) conditions, and samples were prepared in situ. The Au(111) single crystal was cleaned by repetitive Ar+ sputtering and annealing cycles, and its cleanliness was confirmed. ZnBAP and ZnTAP molecules were evaporated from a homemade evaporator held at 633 K. The sample annealing temperature was controlled via a K-type thermocouple directly spot-welded onto the crystal.

ToF-SIMS Measurements

ToF-SIMS measurements were performed with a ToF-SIMS 5 instrument (IONTOF GmbH) on the in situ prepared samples. A 25 keV beam of Bi3+ primary ions was randomly rasterized over an area of 0.25 mm2, and secondary ions were collected using an extraction voltage of 3 kV. For each measurement step, 150 spectra of negative and positive secondary ions were acquired at the same spot, while a new spot was chosen for each new measurement. The total dose density at each single spot was kept below 1012 ions per cm2, which provided the static limit without detectable sample alteration. Mass calibration was performed using the Aun+ cluster signals of the surface. Note that in ToF-SIMS ionization, probability plays a paramount role in signal detection; this in turn makes it very difficult to quantify molecular coverage and is therefore referred to as higher and lower according to the difference in evaporation time. Simulated isotope mass distributions shown above the spectra were calculated using the enviPat web package. (72)

STM Experiments

STM experiments were performed in constant current mode with electrochemically etched tungsten tips. Two different scanning tunneling microscopes were employed, namely a variable-temperature STM (Omicron Nanotechnology GmbH) operated at 50 K and a home-built low-temperature scanning tunneling microscope, operated at 7 K. Images were analyzed using the WSxM software (73) and filtered by global plane subtraction. The parameters of STM image acquisition are provided in Table S3 in the Supporting Information.

XPS Measurements

XPS measurements were performed using a PHOIBOS 100 electron analyzer (Specs GmbH) in normal emission with a nonmonochromatized Al-Kα X-ray source. The binding-energy scale was calibrated using the substrate Au 4f peak position and the Fermi level of the Au crystal. All spectra were normalized to the Au 4f7/2 signals, and background signals obtained on the clean Au(111) crystal were subtracted. Spectra were then fitted using Gaussian/Lorentzian convolution functions for components with simultaneous optimization of the Shirley spectral background by using Unifit 2013 software.

Molecular Modeling

Molecular modeling was performed using HyperChem 8.0 software. Structure optimization of molecules adsorbed onto a 3-layered Au(111) slab was performed using molecular mechanics (Amber force field) with periodic boundary conditions. Au atoms on the surface were kept fixed during the optimization. Occupied and unoccupied state density maps were calculated using extended Hückel theory of the optimized structures.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/jacs.4c12460.

  • Detailed description of ZnBAP/ZnTAP synthesis; overview images; and abundance of fused ZnBAP/ZnTAP molecules; modeled conformations of the native ZnTAP molecule; modeled structures for ZnTAP-20H and ZnTAP-24H molecules, as well as STM imaging parameters (PDF)

Terms & Conditions

Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

Author Information

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  • Corresponding Authors
  • Author
    • Joffrey Pijeat - Université Paris-Saclay, CEA, CNRS, NIMBE, LICSEN, 91191 Gif-sur-Yvette, France
  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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Financial support from the Swiss National Science Foundation (grant numbers 173720, 182082, 212167, and 221265) and the University of Zürich Research Priority Program LightChEC is gratefully acknowledged. This work was financially supported by the FLAG-ERA grant “OPERA” (DFG 437130745 and ANR-19-GRF1-0002-01), the ANR-DFG NLE grant “GRANAO” (DFG 431450789 and ANR-19-CE09-0031-01), the ANR grant “GANESH” (ANR-21-CE09-0025), and a public grant overseen by the French National Research Agency (ANR) as part of the “Investissements d’Avenir” program (Labex NanoSaclay, reference: ANR-10-LABX-0035).

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    A review. The proposal that mols. can perform electronic functions in devices such as diodes, rectifiers, wires and capacitors, or serve as functional materials for electronic or magnetic memory, has stimulated intense research across physics, chem., and engineering for over 35 years. Because biol. uses porphyrins and metalloporphyrins as catalysts, small mol. transporters, elec. conduits, and energy transducers in photosynthesis, porphyrins are an obvious class of mols. to investigate for mol. electronic functions. Of the numerous kinds of mols. under investigation for mol. electronics applications, porphyrins and their related macrocycles are of particular interest because they are robust and their electronic properties can be tuned by chelation of a metal ion and substitution on the macrocycle. The other porphyrinoids have equally variable and adjustable photophys. properties, thus photonic applications are potentiated. At least in the near term, realistic architectures for mol. electronics will require self-organization or nanoprinting on surfaces. This review concs. on self-organized porphyrinoids as components of working electronic devices on electronically active substrates with particular emphasis on the effect of surface, mol. design, mol. orientation and matrix on the detailed electronic properties of single mols.
  4. 4
    Imahori, H.; Fukuzumi, S. Porphyrin- and Fullerene-Based Molecular Photovoltaic Devices. Adv. Funct. Mater. 2004, 14, 525– 536,  DOI: 10.1002/adfm.200305172
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    Porphyrin- and fullerene-based molecular photovoltaic devices
    Imahori, Hiroshi; Fukuzumi, Shunichi
    Advanced Functional Materials (2004), 14 (6), 525-536CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A review. The authors have developed a novel strategy for the construction of mol. photovoltaic devices where the porphyrins and fullerenes employed as building blocks are organized into nanostructured artificial photosynthetic systems by self-assembly processes. Highly efficient photosynthetic energy- and electron-transfer processes take place at gold and indium tin oxide (ITO) electrodes modified with self-assembled monolayers of porphyrin- or fullerene linked systems. Porphyrins and fullerenes also were assembled step by step to make large and uniform clusters on nanostructured semiconductor electrodes, which exhibit a high power-conversion efficiency of ∼1%. These results will provide valuable information on the design of donor-acceptor-type mol. assemblies that can be tailored to construct highly efficient photovoltaic devices.
  5. 5
    Zwick, P.; Dulić, D.; van der Zant, H. S. J.; Mayor, M. Porphyrins as Building Blocks for Single-Molecule Devices. Nanoscale 2021, 13, 15500– 15525,  DOI: 10.1039/D1NR04523G
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    Porphyrins as building blocks for single-molecule devices
    Zwick, Patrick; Dulic, Diana; van der Zant, Herre S. J.; Mayor, Marcel
    Nanoscale (2021), 13 (37), 15500-15525CODEN: NANOHL; ISSN:2040-3372. (Royal Society of Chemistry)
    A review. Direct measurement of single-mol. elec. transparency by break junction expts. has become a major field of research over the two last decades. This review specifically and comprehensively highlights the use of porphyrins as mol. components and discusses their potential use for the construction of future devices. Throughout the review, the features provided by porphyrins, such as low level misalignments and very low attenuation factors, are shown with numerous examples, illustrating the potential and limitations of these mol. junctions, as well as differences emerging from applied integration/investigation techniques.
  6. 6
    Mahmood, A.; Hu, J.-Y.; Xiao, B.; Tang, A.; Wang, X.; Zhou, E. Recent Progress in Porphyrin-Based Materials for Organic Solar Cells. J. Mater. Chem. A 2018, 6, 16769– 16797,  DOI: 10.1039/C8TA06392C
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    Recent progress in porphyrin-based materials for organic solar cells
    Mahmood, Asif; Hu, Jian-Yong; Xiao, Bo; Tang, Ailing; Wang, Xiaochen; Zhou, Erjun
    Journal of Materials Chemistry A: Materials for Energy and Sustainability (2018), 6 (35), 16769-16797CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
    This article is written to provide an up-to-date review of porphyrin-based materials used in org. solar cells (OSCs). During the past two decades, OSCs have been the subject of extensive research and significant efforts have been devoted to developing low-cost OSCs, and they are not far from commercialization. Porphyrin and its analogs have been successfully applied to different optoelectronic devices, esp. attaining remarkable fame when applied in dye sensitized solar cells. Despite the initial failures of their application in OSCs, porphyrins still attract much attention because of their structural versatility and recently realized significant improvement. In this review, we focus on summarizing the recent progress in porphyrin-based photovoltaic materials, including polymers, dyads, triads, small-mols., and so on. We hope this paper could provide an in-depth study on the structure-property-performance relationship and provide a guideline for the further development of porphyrin-based and even other photovoltaic materials.
  7. 7
    Li, L.-L.; Diau, E. W.-G. Porphyrin-Sensitized Solar Cells. Chem. Soc. Rev. 2013, 42, 291– 304,  DOI: 10.1039/C2CS35257E
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    Porphyrin-sensitized solar cells
    Li, Lu-Lin; Diau, Eric Wei-Guang
    Chemical Society Reviews (2013), 42 (1), 291-304CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
    A review. Nature has chosen chlorophylls in plants as antennae to harvest light for the conversion of solar energy in complicated photosynthetic processes. Inspired by natural photosynthesis, scientists utilized artificial chlorophylls - the porphyrins - as efficient centers to harvest light for solar cells sensitized with a porphyrin (PSSC). After the first example appeared in 1993 of a porphyrin of type copper chlorophyll as a photosensitizer for PSSC that achieved a power conversion efficiency of 2.6%, no significant advance of PSSC was reported until 2005; beta-linked zinc porphyrins were then reported to show promising device performances with a benchmark efficiency of 7.1% reported in 2007. Meso-linked zinc porphyrin sensitizers in the first series with a push-pull framework appeared in 2009; the best cell performed comparably to that of a N3-based device, and a benchmark 11% was reported for a porphyrin sensitizer of this type in 2010. With a structural design involving long alkoxyl chains to envelop the porphyrin core to suppress the dye aggregation for a push-pull zinc porphyrin, the PSSC achieved a record 12.3% in 2011 with co-sensitization of an org. dye and a cobalt-based electrolyte. The best PSSC system exhibited a panchromatic feature for light harvesting covering the visible spectral region to 700 nm, giving opportunities to many other porphyrins, such as fused and dimeric porphyrins, with near-IR absorption spectral features, together with the approach of mol. co-sensitization, to enhance the device performance of PSSC. According to this historical trend for the development of prospective porphyrin sensitizers used in PSSC, we review systematically the progress of porphyrins of varied kinds, and their derivs., applied in PSSC with a focus on reports during 2007-2012 from the point of view of mol. design correlated with photovoltaic performance.
  8. 8
    Paolesse, R.; Nardis, S.; Monti, D.; Stefanelli, M.; Di Natale, C. Porphyrinoids for Chemical Sensor Applications. Chem. Rev. 2017, 117, 2517– 2583,  DOI: 10.1021/acs.chemrev.6b00361
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    Porphyrinoids for Chemical Sensor Applications
    Paolesse, Roberto; Nardis, Sara; Monti, Donato; Stefanelli, Manuela; Di Natale, Corrado
    Chemical Reviews (Washington, DC, United States) (2017), 117 (4), 2517-2583CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    Porphyrins and related macrocycles have been intensively exploited as sensing materials in chem. sensors, since in these devices they mimic most of their biol. functions, such as reversible binding, catalytic activation, and optical changes. Such a magnificent bouquet of properties allows applying porphyrin derivs. to different transducers, ranging from nanogravimetric to optical devices, also enabling the realization of multifunctional chem. sensors, in which multiple transduction mechanisms are applied to the same sensing layer. Potential applications are further expanded through sensor arrays, where cross-selective sensing layers can be applied for the anal. of complex chem. matrixes. The possibility of finely tuning the macrocycle properties by synthetic modification of the different components of the porphyrin ring, such as peripheral substituents, mol. skeleton, coordinated metal, allows creating a vast library of porphyrinoid-based sensing layers. From among these, one can select optimal arrays for a particular application. This feature is particularly suitable for sensor array applications, where cross-selective receptors are required. This Review briefly describes chem. sensor principles. The main part of the Review is divided into two sections, describing the porphyrin-based devices devoted to the detection of gaseous or liq. samples, according to the corresponding transduction mechanism. Although most devices are based on porphyrin derivs., seminal examples of the application of corroles or other porphyrin analogs are evidenced in dedicated sections.
  9. 9
    Park, J. M.; Hong, K.-I.; Lee, H.; Jang, W.-D. Bioinspired Applications of Porphyrin Derivatives. Acc. Chem. Res. 2021, 54, 2249– 2260,  DOI: 10.1021/acs.accounts.1c00114
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    Bioinspired Applications of Porphyrin Derivatives
    Park, Jong Min; Hong, Kyeong-Im; Lee, Hosoowi; Jang, Woo-Dong
    Accounts of Chemical Research (2021), 54 (9), 2249-2260CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
    Conspectus: Porphyrin derivs. are ubiquitous in nature and have important biol. roles, such as in light harvesting, oxygen transport, and catalysis. Owing to their intrinsic π-conjugated structure, porphyrin derivs. exhibit characteristic photophys. and electrochem. properties. In biol. systems, porphyrin derivs. are assocd. with various protein mols. through noncovalent interactions. For example, Hb, which is responsible for oxygen transport in most vertebrates, consists of four subunits of a globular protein with an iron porphyrin deriv. prosthetic group. Furthermore, noncovalently arranged porphyrin derivs. are the fundamental chromophores in light-harvesting systems for photosynthesis in plants and algae. These biol. important roles originate from the functional versatility of porphyrin derivs. Specifically, porphyrins are excellent host compds., forming coordination complexes with various metal ions that adds functionality to the porphyrin unit, such as redox activity and addnl. ligand binding at the central metal ion. In addn., porphyrins are useful building blocks for functional supramol. assemblies because of their flat and sym. mol. architectures, and their excellent photophys. properties are typically utilized for the fabrication of bioactive functional materials. In this Account, we summarize our endeavors over the past decade to develop functional materials based on porphyrin derivs. using bioinspired approaches. In the first section, we discuss several synthetic receptors that act as artificial allosteric host systems and can be used for the selective detection of various chems., such as cyanide, chloride, and amino acids. In the second section, we introduce multiporphyrin arrays as mimics of natural light-harvesting complexes. The active control of energy transfer processes by addnl. guest binding and the fabrication of org. photovoltaic devices using porphyrin derivs. are also introduced. In the third section, we introduce several types of porphyrin-based supramol. assemblies. Through noncovalent interactions such as metal-ligand interaction, hydrogen bonding, and π-π interaction, porphyrin derivs. were constructed as supramol. polymers with formation of fiber or toroidal assembly. In the last section, the application of porphyrin derivs. for biomedical nanodevice fabrication is introduced. Even though porphyrins were good candidates as photosensitizers for photodynamic therapy, they have limitations for biomedical application owing to aggregation in aq. media. We suggested ionic dendrimer porphyrins and they showed excellent photodynamic therapy (PDT) efficacy.
  10. 10
    Lindsey, J. S.; Prathapan, S.; Johnson, T. E.; Wagner, R. W. Porphyrin Building Blocks for Modular Construction of Bioorganic Model Systems. Tetrahedron 1994, 50, 8941– 8968,  DOI: 10.1016/S0040-4020(01)85364-3
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    Porphyrin building blocks for modular construction of bioorganic model systems
    Lindsey, Jonathan S.; Prathapan, Sreedharan; Johnson, Thomas E.; Wagner, Richard W.
    Tetrahedron (1994), 50 (30), 8941-68CODEN: TETRAB; ISSN:0040-4020.
    The authors outline a modular building block strategy for the covalent assembly of porphyrin-contg. model systems. Mol. design issues for the synthesis of porphyrin dimers, dye-porphyrin dyads, and multi-porphyrin arrays have been used to guide the development of this approach. The major design constraints are to achieve directed coupling of free base and/or metalloporphyrin building blocks in dil. soln. under non-acidic non-metalating conditions. A set of 24 porphyrin building blocks has been synthesized. The porphyrins are prepd. by reaction of substituted benzaldehydes with pyrrole using the two-step one-flask room temp. porphyrin synthesis. Routes to 7 substituted aldehydes are described. Each porphyrin bears one or four functional groups, and many also are facially-encumbered in order to achieve increased soly. Twelve functional groups that meet the design criteria include those that can be reacted directly in coupling reactions such as active esters, α-chloroacetamido, benzoyl, and iodo groups, and others that require deprotection prior to coupling, such as phthalimidomethyl, FMOC-prolyl, trimethylsilylethynyl, dithiolane, methoxycarbonyl, and trimethylsilylethoxycarbonyl groups. The synthesis of 13 porphyrin dimers and dye-porphyrin dyads has been explored as a testbed for refining strategies for the synthesis of mol. devices contg. multiple porphyrins and other components. The coupling strategies investigated have yielded dimers or dyads with subunits linked by amide, butadiyne, ethyne, or thiourea groups. This building block approach should enable rapid assembly of architecturally-defined porphyrin-based model systems.
  11. 11
    Auwärter, W.; Écija, D.; Klappenberger, F.; Barth, J. V. Porphyrins at Interfaces. Nat. Chem. 2015, 7, 105– 120,  DOI: 10.1038/nchem.2159
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    11
    Porphyrins at interfaces
    Auwarter Willi; Klappenberger Florian; Barth Johannes V; Ecija David
    Nature chemistry (2015), 7 (2), 105-20 ISSN:.
    Porphyrins and other tetrapyrrole macrocycles possess an impressive variety of functional properties that have been exploited in natural and artificial systems. Different metal centres incorporated within the tetradentate ligand are key for achieving and regulating vital processes, including reversible axial ligation of adducts, electron transfer, light-harvesting and catalytic transformations. Tailored substituents optimize their performance, dictating their arrangement in specific environments and mediating the assembly of molecular nanoarchitectures. Here we review the current understanding of these species at well-defined interfaces, disclosing exquisite insights into their structural and chemical properties, and also discussing methods by which to manipulate their intramolecular and organizational features. The distinct characteristics arising from the interfacial confinement offer intriguing prospects for molecular science and advanced materials. We assess the role of surface interactions with respect to electronic and physicochemical characteristics, and describe in situ metallation pathways, molecular magnetism, rotation and switching. The engineering of nanostructures, organized layers, interfacial hybrid and bio-inspired systems is also addressed.
  12. 12
    Gottfried, J. M. Surface Chemistry of Porphyrins and Phthalocyanines. Surf. Sci. Rep. 2015, 70, 259– 379,  DOI: 10.1016/j.surfrep.2015.04.001
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    Surface chemistry of porphyrins and phthalocyanines
    Gottfried, J. Michael
    Surface Science Reports (2015), 70 (3), 259-379CODEN: SSREDI; ISSN:0167-5729. (Elsevier B.V.)
    This review covers the surface chem. of porphyrins, phthalocyanines, their metal complexes, and related compds., with particular focus on chem. reactions at solid/vacuum interfaces. Porphyrins are not only important biomols., they also find, together with the artificial phthalocyanines, numerous technol. and scientific applications, which often involve surface and interface related aspects. After a brief summary of fundamental properties of these mols. in the context of surface science, the following topics will be discussed: (1) Aspects of geometric structure, including self-assembly, conformation, mobility and manipulation of the adsorbed mols. (2) Surface-related changes of the electronic structure and the magnetic properties. (3) The role of the metal center in the surface chem. bond. (4) On-surface coordination reactions, such as direct metalation and coordination of axial ligands. (5) The influence of axial ligands on the surface chem. bond and the magnetic properties.
  13. 13
    Sun, Q.; Mateo, L. M.; Robles, R.; Ruffieux, P.; Lorente, N.; Bottari, G.; Torres, T.; Fasel, R. Inducing Open-Shell Character in Porphyrins through Surface-Assisted Phenalenyl π-Extension. J. Am. Chem. Soc. 2020, 142, 18109– 18117,  DOI: 10.1021/jacs.0c07781
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    13
    Inducing Open-Shell Character in Porphyrins through Surface-Assisted Phenalenyl π-Extension
    Sun, Qiang; Mateo, Luis M.; Robles, Roberto; Ruffieux, Pascal; Lorente, Nicolas; Bottari, Giovanni; Torres, Tomas; Fasel, Roman
    Journal of the American Chemical Society (2020), 142 (42), 18109-18117CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Org. open-shell compds. are extraordinarily attractive materials for their use in mol. spintronics thanks to their long spin-relaxation times and structural flexibility. Porphyrins (Pors) have widely been used as mol. platforms to craft persistent open-shell structures through soln.-based redox chem. However, very few examples of inherently open-shell Pors have been reported, which are typically obtained through the fusion of non-Kekul´e polyarom. hydrocarbon moieties to the Por core. The inherent instability and low soly. of these radical species, however, requires the use of bulky substituents and multistep synthetic approaches. On-surface synthesis has emerged as a powerful tool to overcome such limitations, giving access to structures that cannot be obtained through classical methods. Herein, we present a simple and straightforward method for the on-surface synthesis of phenalenyl-fused Pors using readily available mol. precursors. In a systematic study, we examine the structural and electronic properties of three surface-supported Pors, bearing zero, two (PorA2), and four (PorA4) meso-fused phenalenyl moieties. Through atomically resolved real-space imaging by scanning probe microscopy and high-resoln. scanning tunneling spectroscopy combined with d. functional theory calcns., we unambiguously demonstrate a triplet ground state for PorA2 and a charge-transfer-induced open-shell character for the intrinsically closed-shell PorA4.
  14. 14
    Sun, Q.; Mateo, L. M.; Robles, R.; Ruffieux, P.; Bottari, G.; Torres, T.; Fasel, R.; Lorente, N. Magnetic Interplay between π-Electrons of Open-Shell Porphyrins and d-Electrons of Their Central Transition Metal Ions. Adv. Sci. 2022, 9, 2105906  DOI: 10.1002/advs.202105906
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    14
    Magnetic Interplay between p-Electrons of Open-Shell Porphyrins and d-Electrons of Their Central Transition Metal Ions
    Sun, Qiang; Mateo, Luis M.; Robles, Roberto; Ruffieux, Pascal; Bottari, Giovanni; Torres, Tomas; Fasel, Roman; Lorente, Nicolas
    Advanced Science (Weinheim, Germany) (2022), 9 (19), 2105906CODEN: ASDCCF; ISSN:2198-3844. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Magnetism is typically assocd. with d- or f-block elements, but can also appear in org. mols. with unpaired p-electrons. This has considerably boosted the interest in such org. materials with large potential for spintronics and quantum applications. While several materials showing either d/f or p-electron magnetism have been synthesized, the combination of both features within the same structure has only scarcely been reported. Open-shell porphyrins (Pors) incorporating d-block transition metal ions represent an ideal platform for the realization of such architectures. Herein, the prepn. of a series of open-shell, p-extended Pors that contain magnetically active metal ions (i.e., CuII, CoII, and FeII) through a combination of in-soln. and on-surface synthesis is reported. A detailed study of the magnetic interplay between p- and d-electrons in these metalloPors has been performed by scanning probe methods and d. functional theory calcns. For the Cu and FePors, ferromagnetically coupled p-electrons are detd. to be delocalized over the Por edges. For the CoPor, the authors find a Kondo resonance resulting from the singly occupied CoIIdz2 orbital to dominate the magnetic fingerprint. The Fe deriv. exhibits the highest magnetization of 3.67μB (S≈2) and an exchange coupling of 16 meV between the p-electrons and the Fe d-states.
  15. 15
    Baklanov, A.; Garnica, M.; Robert, A.; Bocquet, M.-L.; Seufert, K.; Küchle, J. T.; Ryan, P. T. P.; Haag, F.; Kakavandi, R.; Allegretti, F.; Auwärter, W. On-Surface Synthesis of Nonmetal Porphyrins. J. Am. Chem. Soc. 2020, 142, 1871– 1881,  DOI: 10.1021/jacs.9b10711
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    15
    On-Surface Synthesis of Nonmetal Porphyrins
    Baklanov, Aleksandr; Garnica, Manuela; Robert, Anton; Bocquet, Marie-Laure; Seufert, Knud; Kuechle, Johannes T.; Ryan, Paul T. P.; Haag, Felix; Kakavandi, Reza; Allegretti, Francesco; Auwaerter, Willi
    Journal of the American Chemical Society (2020), 142 (4), 1871-1881CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    We report the on-surface synthesis of a nonmetal porphyrin, namely, silicon tetraphenylporphyrin (Si-TPP), by the deposition of at. silicon onto a free-base TPP layer on a Ag(100) surface under ultrahigh vacuum (UHV) conditions. Scanning tunneling microscopy provides insights into the self-assembly of the TPP mols. before and after Si insertion. Silicon coordinates with all four nitrogen atoms of the TPP macrocycle and interacts with a silver atom of the substrate as confirmed by scanning tunneling spectroscopy, XPS, and complementary d. functional theory calcns. The Si-TPP complex presents a saddle-shaped conformation that is stable under STM manipulation. Our study shows how protocols established for the on-surface metalation of tetrapyrroles can be adopted to achieve nonmetal porphyrins. Complementary expts. yielding Si-TPP and Ge-TPP on Ag(111) highlight the applicability to different main group elements and supports. The success of our nonmetal porphyrin synthesis procedure is further corroborated by a temp.-programmed desorption expt., revealing the desorption of Ge-TPP. This extension of interfacial complex formation beyond metal elements opens promising prospects for new tetrapyrrole architectures with distinct properties and functionalities.
  16. 16
    Chen, H.; Tao, L.; Wang, D.; Wu, Z.-Y.; Zhang, J.-L.; Gao, S.; Xiao, W.; Du, S.; Ernst, K.-H.; Gao, H.-J. Stereoselective On-Surface Cyclodehydrofluorization of a Tetraphenylporphyrin and Homochiral Self-Assembly. Angew. Chem., Int. Ed. 2020, 59, 17413– 17416,  DOI: 10.1002/anie.202005425
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    Stereoselective On-Surface Cyclodehydrofluorization of a Tetraphenylporphyrin and Homochiral Self-Assembly
    Chen, Hui; Tao, Lei; Wang, Dongfei; Wu, Zhuo-Yan; Zhang, Jun-Long; Gao, Song; Xiao, Wende; Du, Shixuan; Ernst, Karl-Heinz; Gao, Hong-Jun
    Angewandte Chemie, International Edition (2020), 59 (40), 17413-17416CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The thermally induced cyclodehydrofluorization of iron tetrakis(pentafluorophenyl)porphyrin proceeded highly stereoselectively to give a prochiral product on a gold surface in an ultrahigh vacuum, whereas dehydrocyclization of the resp. iron tetrakisphenylporphyrin did not show such selectivity. Stereoselectivity was predominantly obsd. for closely packed layers, which is an indication of intermol. cooperativity and steric constraints induced by adjacent species. D. functional theory identified intermol. packing constraints as the origin of such selectivity during the reaction. Scanning tunneling microscopy revealed the formation of an enantiomerically pure two-dimensional self-assembly as a conglomerate of mirror domains. On-surface two-dimensional topochem., as reported herein, may open new routes for stereoselective synthesis.
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    Zhao, Y.; Jiang, K.; Li, C.; Liu, Y.; Xu, C.; Zheng, W.; Guan, D.; Li, Y.; Zheng, H.; Liu, C.; Luo, W.; Jia, J.; Zhuang, X.; Wang, S. Precise Control of π-Electron Magnetism in Metal-Free Porphyrins. J. Am. Chem. Soc. 2020, 142, 18532– 18540,  DOI: 10.1021/jacs.0c07791
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    Precise Control of π-Electron Magnetism in Metal-Free Porphyrins
    Zhao, Yan; Jiang, Kaiyue; Li, Can; Liu, Yufeng; Xu, Chengyang; Zheng, Wenna; Guan, Dandan; Li, Yaoyi; Zheng, Hao; Liu, Canhua; Luo, Weidong; Jia, Jinfeng; Zhuang, Xiaodong; Wang, Shiyong
    Journal of the American Chemical Society (2020), 142 (43), 18532-18540CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    The porphyrin macrocycle can stabilize a set of magnetic metal ions, thus introducing localized net spins near the center. However, it remains elusive but most desirable to introduce delocalized spins in porphyrins with wide implications, for example, for building correlated quantum spins. Here, we demonstrate that metal-free porphyrins host delocalized π-electron magnetism, as revealed by scanning probe microscopy and a different level of theory calcns. Our results demonstrate that engineering of π-electron topologies introduces a spin-polarized singlet state and delocalized net spins in metal-free porphyrins. In addn., the π-electron magnetism can be switched on/off via scanning tunneling microscope manipulation by tuning the interfacial charge transfer. Our results provide an effective way to precisely control the π-electron magnetism in metal-free porphyrins, which can be further extended to design new magnetic functionalities of porphyrin-based architectures.
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    Rascon, E. C.; Riss, A.; Matěj, A.; Wiengarten, A.; Mutombo, P.; Soler, D.; Jelinek, P.; Auwärter, W. On-Surface Synthesis of Square-Type Porphyrin Tetramers with Central Antiaromatic Cyclooctatetraene Moiety. J. Am. Chem. Soc. 2023, 145, 967– 977,  DOI: 10.1021/jacs.2c10088
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    18
    On-Surface Synthesis of Square-Type Porphyrin Tetramers with Central Antiaromatic Cyclooctatetraene Moiety
    Rascon, Eduardo Corral; Riss, Alexander; Matej, Adam; Wiengarten, Alissa; Mutombo, Pingo; Soler, Diego; Jelinek, Pavel; Auwaerter, Willi
    Journal of the American Chemical Society (2023), 145 (2), 967-977CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    The synthesis of two-dimensionally extended polycyclic heteroat. mols. keeps attracting considerable attention. In particular, frameworks bearing planar cyclooctatetraenes (COT) moieties can display intriguing properties, including antiaromaticity. Here, the authors present an on-surface chem. route to square-type porphyrin tetramers with a central COT ring, coexisting with other oligomers. This approach employing temp.-induced dehydrogenative porphyrin homocoupling in an ultrahigh vacuum environment provides access to surface-supported, unsubstituted porphyrin tetramers that are not easily achievable by conventional synthesis means. Specifically, monomeric free-base (2H-P) and Zn-metalated (Zn-P) porphines (P) were employed to form square-type free-base and Zn-functionalized tetramers on Ag(100). An at.-level characterization by bond-resolved at. force microscopy and scanning tunneling microscopy and spectroscopy is provided, identifying the mol. structures. Complemented by d. functional theory modeling, the electronic structure is elucidated, indeed revealing antiaromaticity induced by the COT moiety. The present study thus gives access, and insights, to a porphyrin oligomer, representing both a model system for directly fused porphyrins and a potential building block for conjugated, extended two-dimensional porphyrin sheets.
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    Otsuki, J. STM Studies on Porphyrins. Coord. Chem. Rev. 2010, 254, 2311– 2341,  DOI: 10.1016/j.ccr.2009.12.038
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    STM studies on porphyrins
    Otsuki, Joe
    Coordination Chemistry Reviews (2010), 254 (19-20), 2311-2341CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
    A review. Porphyrins are promising components to be used in mol. electronics due to their rich electronic/photonic properties. Prepn. of supramol. architectures of porphyrins on solid surfaces would constitute a basis for further development toward mol. circuitry or other constructs for mol. electronics applications. Assemblies on surfaces can be probed with scanning tunneling microscopy (STM) at submol. resolns. to reveal the arrangements and conformations of mols. on an individual mol. basis. The electronic characteristics within a single porphyrin mol. can also be probed by means of the same technique. This review summarizes the status quo of STM studies on porphyrins on surfaces with regard to their assemblies, structures, and electronic properties at the single mol. level.
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    Zhang, Y.; Lu, J.; Zhou, H.; Zhang, G.; Ruan, Z.; Zhang, Y.; Zhang, H.; Sun, S.; Niu, G.; Fu, B.; Yang, B.; Chen, L.; Gao, L.; Cai, J. Highly Regioselective Cyclodehydrogenation of Diphenylporphyrin on Metal Surfaces. ACS Nano 2023, 17, 13575– 13583,  DOI: 10.1021/acsnano.3c02204
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    Wu, F.; Zhan, S.; Yang, L.; Zhuo, Z.; Wang, X.; Li, X.; Luo, Y.; Jiang, J. Spatial Confinement of a Carbon Nanocone for an Efficient Oxygen Evolution Reaction. J. Phys. Chem. Lett. 2021, 12, 2252– 2258,  DOI: 10.1021/acs.jpclett.1c00267
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    Spatial Confinement of a Carbon Nanocone for an Efficient Oxygen Evolution Reaction
    Wu, Fan; Zhan, Shaoqi; Yang, Li; Zhuo, Zhiwen; Wang, Xijun; Li, Xiyu; Luo, Yi; Jiang, Jun
    Journal of Physical Chemistry Letters (2021), 12 (9), 2252-2258CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    A major bottleneck of large-scale water splitting for hydrogen prodn. is the lack of catalysts for the oxygen evolution reaction (OER) with low cost and high efficiency. In this work, we proposed an electrocatalyst of a curved carbon nanocone embedded with two TMN4 active sites (TM = transition metal) and used first-principles calcns. to investigate their OER mechanisms and catalytic activities. In the particular spatial confinement of a curved nanocone, we found that the distance between intermediates adsorbed on two active sites is shorter than the distance between these two active sites. This finding can be used to enhance OER activity by distance-dependent interaction between intermediates through two different mechanisms. The first mechanism in which an O2 mol. is generated from two neighboring *O intermediates exhibits a linear activity trend, and the lowest overpotential is 0.27 V for the FeN4 system. In the second mechanism, selective stabilization of the *OOH intermediate is realized, leading to a new scaling relationship (ΔG*OOH = ΔG*OH + 3.04 eV) assocd. with a modified OER activity volcano (theor. volcano apex at 0.29 V). The studied mechanisms of the spatial confinement of a carbon nanocone provide a new perspective for designing efficient OER catalysts.
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    Hiroto, S.; Miyake, Y.; Shinokubo, H. Synthesis and Functionalization of Porphyrins through Organometallic Methodologies. Chem. Rev. 2017, 117, 2910– 3043,  DOI: 10.1021/acs.chemrev.6b00427
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    Synthesis and Functionalization of Porphyrins through Organometallic Methodologies
    Hiroto, Satoru; Miyake, Yoshihiro; Shinokubo, Hiroshi
    Chemical Reviews (Washington, DC, United States) (2017), 117 (4), 2910-3043CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    This review focuses on the postfunctionalization of porphyrins and related compds. through catalytic and stoichiometric organometallic methodologies. The employment of organometallic reactions has become common in porphyrin synthesis. Palladium-catalyzed cross-coupling reactions are now std. techniques for constructing carbon-carbon bonds in porphyrin synthesis. In addn., iridium- or palladium-catalyzed direct C-H functionalization of porphyrins is emerging as an efficient way to install various substituents onto porphyrins. Furthermore, the copper-mediated Huisgen cycloaddn. reaction has become a frequent strategy to incorporate porphyrin units into functional mols. The use of these organometallic techniques, along with the traditional porphyrin synthesis, now allows chemists to construct a wide range of highly elaborated and complex porphyrin architectures.
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    Mandal, A. K.; Taniguchi, M.; Diers, J. R.; Niedzwiedzki, D. M.; Kirmaier, C.; Lindsey, J. S.; Bocian, D. F.; Holten, D. Photophysical Properties and Electronic Structure of Porphyrins Bearing Zero to Four Meso-Phenyl Substituents: New Insights into Seemingly Well Understood Tetrapyrroles. J. Phys. Chem. A 2016, 120, 9719– 9731,  DOI: 10.1021/acs.jpca.6b09483
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    Photophysical Properties and Electronic Structure of Porphyrins Bearing Zero to Four meso-Phenyl Substituents: New Insights into Seemingly Well Understood Tetrapyrroles
    Mandal, Amit Kumar; Taniguchi, Masahiko; Diers, James R.; Niedzwiedzki, Dariusz M.; Kirmaier, Christine; Lindsey, Jonathan S.; Bocian, David F.; Holten, Dewey
    Journal of Physical Chemistry A (2016), 120 (49), 9719-9731CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
    Six free base porphyrins bearing 0-4 meso substituents have been examd. by steady-state and time-resolved absorption and fluorescence spectroscopy in both toluene and N,N-dimethylformamide (DMF). The lifetime of the lowest singlet excited state (S1) decreases with an increase in the no. of meso-Ph groups; the values in toluene are H2P-0 (15.5 ns) > H2P-1 (14.9 ns) > H2P-2c (14.4 ns) > H2P-2t (13.8 ns) ∼ H2P-3 (13.8 ns) > H2P4 ≈ (12.8 ns), where "H2P" refers to the core free base porphyrin, the numerical suffix indicates the no. of meso-Ph groups, and "c" and "t" refer to cis and trans, resp. The opposite trend is found for the fluorescence quantum yield; the values in toluene are H2P-0 (0.049) < H2P-1 (0.063) ∼ H2P-2c (0.063) < H2P-2t (0.071) < H2P-3 (0.073) < H2P‾4 (0.090). Similar trends occur in DMF. All radiative and nonradiative (internal conversion and intersystem crossing) rate consts. for S1 decay increase with increasing no. of meso-Ph groups. The increase in the rate const. for fluorescence parallels an increase in oscillator strength of the S0 → S1 absorption manifold. The trend is reproduced by time-dependent d. functional theory calcns. The calcns. within the context of the four-orbital model reveal that the enhanced S0 ↔ S1 radiative probabilities derive from a preferential effect of the meso-Ph groups to raise the energy of the HOMO, which underpins a parallel bathochromic shift in the S0 → S1 absorption wavelength. Polarizations of the S1 and S2 excited states with respect to mol. structural features (e.g., the central proton axis) are analyzed in the context of historical conventions for porphyrins vs. chlorins and bacteriochlorins, where some ambiguity exists, including for porphine, one of the simplest tetrapyrroles. Collectively, the study affords fundamental insights into the photophys. properties and electronic structure of meso-phenylporphyrins that should aid their continued widespread use as benchmarks for tetrapyrrole-based architectures in chem., solar-energy and life-sciences research.
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    Suijkerbuijk, B. M. J. M.; Klein Gebbink, R. J. M. Merging Porphyrins with Organometallics: Synthesis and Applications. Angew. Chem. Int. Ed 2008, 47, 7396– 7421,  DOI: 10.1002/anie.200703362
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    Merging porphyrins with organometallics: synthesis and applications
    Suijkerbuijk, Bart M. J. M.; Klein Gebbink, Robertus J. M.
    Angewandte Chemie, International Edition (2008), 47 (39), 7396-7421CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A review. The coordination chem. of porphyrins has traditionally involved the ability of the porphyrin's tetrapyrrolic core to accommodate metal ions of varying charges and sizes, and on the organometallic chem. of the resulting metalloporphyrins. However, the organometallic chem. of porphyrins is not necessarily restricted to the metal bound in the porphyrin core, but can also be extended to the porphyrin periphery, be it through direct metalation of the porphyrin macrocycle at the meso or β position, or by attachment to or merger of the porphyrin skeleton with ligands, followed by metalation. This Review focuses on the synthetic strategies used for porphyrins with peripheral metal-carbon bonds. The exciting results that have been produced underscore the importance and future potential of this field.
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    Pijeat, J.; Dappe, Y. J.; Thuéry, P.; Campidelli, S. Synthesis and Suzuki–Miyaura Cross Coupling Reactions for Post-Synthetic Modification of a Tetrabromo-Anthracenyl Porphyrin. Org. Biomol. Chem. 2018, 16, 8106– 8114,  DOI: 10.1039/C8OB02150C
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    Cooper, C.; Paul, R.; Alsaleh, A.; Washburn, S.; Rackers, W.; Kumar, S.; Nesterov, V. N.; D’Souza, F.; Vinogradov, S. A.; Wang, H. Naphthodithiophene-Fused Porphyrins: Synthesis, Characterization, and Impact of Extended Conjugation on Aromaticity. Chem. - Eur. J. 2023, 29, e202302013  DOI: 10.1002/chem.202302013
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    Davis, N. K. S.; Thompson, A. L.; Anderson, H. L. A Porphyrin Fused to Four Anthracenes. J. Am. Chem. Soc. 2011, 133, 30– 31,  DOI: 10.1021/ja109671f
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    A Porphyrin Fused to Four Anthracenes
    Davis, Nicola K. S.; Thompson, Amber L.; Anderson, Harry L.
    Journal of the American Chemical Society (2011), 133 (1), 30-31CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    The authors synthesized a fused tetraanthracenylporphyrin by oxidn. of a meso-anthracenyl nickel(II) porphyrin with FeCl3. This compd. exhibits an intense red shifted absorption spectrum (λmax = 1417 nm; ε = 1.2 × 105 M-1 cm-1) and a small electrochem. HOMO-LUMO gap (0.61 eV). The crystal structure shows that it forms π-stacked dimers with a short Ni···Ni distance (3.32 Å).
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    Davis, N. K. S.; Thompson, A. L.; Anderson, H. L. Bis-Anthracene Fused Porphyrins: Synthesis, Crystal Structure, and Near-IR Absorption. Org. Lett. 2010, 12, 2124– 2127,  DOI: 10.1021/ol100619p
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    Bis-Anthracene Fused Porphyrins: Synthesis, Crystal Structure, and Near-IR Absorption
    Davis, Nicola K. S.; Thompson, Amber L.; Anderson, Harry L.
    Organic Letters (2010), 12 (9), 2124-2127CODEN: ORLEF7; ISSN:1523-7060. (American Chemical Society)
    Synthesis of fused bis-anthracene porphyrin monomers and dimers was achieved by oxidative ring closure using FeCl3 and Sc(OTf)3/DDQ, resp. The fused compds. display red-shifted absorption spectra with maxima in the near-IR at 973 and 1495 nm, resp., and small electrochem. HOMO-LUMO gaps. The crystal structure of the fully fused bis-anthracene porphyrin shows that it has a regular planar π-system.
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    Kurotobi, K.; Kim, K. S.; Noh, S. B.; Kim, D.; Osuka, A. A Quadruply Azulene-Fused Porphyrin with Intense Near-IR Absorption and a Large Two-Photon Absorption Cross Section. Angew. Chem., Int. Ed. 2006, 45, 3944– 3947,  DOI: 10.1002/anie.200600892
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    A quadruply azulene-fused porphyrin with intense near-IR absorption and a large two-photon absorption cross section
    Kurotobi, Kei; Kim, Kil Suk; Noh, Su Bum; Kim, Dongho; Osuka, Atsuhiro
    Angewandte Chemie, International Edition (2006), 45 (24), 3944-3947CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Azulene-fused nickel porphyrins I-III [Ar = 3,5-(Me3C)2C6H3; R = 2,4,6-(Me3C)3C6H2] were synthesized through the oxidn. of meso-(4-azulenyl)porphyrins with FeCl3. The azulene-fused strategy allowed prepn. of highly ρ-conjugated porphyrinic electronic systems, which show promise as two-photon absorption pigments.
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    Davis, N. K. S.; Pawlicki, M.; Anderson, H. L. Expanding the Porphyrin π-System by Fusion with Anthracene. Org. Lett. 2008, 10, 3945– 3947,  DOI: 10.1021/ol801500b
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    Expanding the Porphyrin π-System by Fusion with Anthracene
    Davis, Nicola K. S.; Pawlicki, Milosz; Anderson, Harry L.
    Organic Letters (2008), 10 (18), 3945-3947CODEN: ORLEF7; ISSN:1523-7060. (American Chemical Society)
    Synthesis of β,meso,β-anthracene triply fused and β,meso-anthracene doubly fused porphyrins was achieved via oxidative intramol. ring closure of meso-(9-anthryl)porphyrins and meso-(1-anthryl)porphyrins, resp. Fusion was only possible when the anthracene carried electron-donating alkoxy substituents. The fused porphyrins exhibit strongly red shifted UV-visible absorption spectra and reduced electrochem. HOMO-LUMO gaps (relative to the unfused tetraaryl porphyrin precursor).
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    Gill, H. S.; Harmjanz, M.; Santamaría, J.; Finger, I.; Scott, M. J. Facile Oxidative Rearrangement of Dispiro-Porphodimethenes to Nonplanar and Sheetlike Porphyrins with Intense Absorptions in the Near-IR Region. Angew. Chem., Int. Ed. 2004, 43, 485– 490,  DOI: 10.1002/anie.200352762
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    Facile oxidative rearrangement of dispiro-porphodimethenes to nonplanar and sheetlike porphyrins with intense absorptions in the near-IR region
    Gill, Hubert S.; Harmjanz, Michael; Santamaria, Javier; Finger, Isaac; Scott, Michael J.
    Angewandte Chemie, International Edition (2004), 43 (4), 485-490CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The dispiro-porphodimethene (I, Ar = mesityl; R = H, tert-butyl) was prepd. and metalated with Cu or Pd. These Cu and Pd dispiro-porphodimethene complexes were then oxidized with rearrangement to yield complexes of the corresponding cycloheptanones (II, III). Complexes of II or III were then further oxidized to yield Cu and Pd complexes of IV and V. Exceedingly large, planar porphyrin systems composed of 49 nonhydrogen nuclei in highly delocalized at. systems display exceptionally low-energy transitions in UV/visible/NIR spectroscopy and in cyclic voltammetry. The spectra shown are for cis Pd complex depicted and the corresponding trans isomer.
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    Diev, V. V.; Hanson, K.; Zimmerman, J. D.; Forrest, S. R.; Thompson, M. E. Fused Pyrene–Diporphyrins: Shifting Near-Infrared Absorption to 1.5 Mm and Beyond. Angew. Chem., Int. Ed. 2010, 49, 5523– 5526,  DOI: 10.1002/anie.201002669
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    Fused Pyrene-Diporphyrins: Shifting Near-Infrared Absorption to 1.5 μm and Beyond
    Diev, Vyacheslav V.; Hanson, Kenneth; Zimmerman, Jeramy D.; Forrest, Stephen R.; Thompson, Mark E.
    Angewandte Chemie, International Edition (2010), 49 (32), 5523-5526, S5523/1-S5523/21CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The prepn. of a new class of diporphyrin-pyrene hybrid compds. via a relatively simple method is reported. The key step is the oxidative ring closure of the pyrene with the porphyrin core. Pyrene-substituted zinc porphyrin fused dimer I (Ar = 3,5-di-tert-butylphenyl) was prepd. in two steps (Suzuki coupling and Osuka's oxidative fusion of porphyrin rings) starting from a disubstituted zinc metalloporphyrin. Double fusion of two pyrene rings with the diporphyrin moiety to give II (M = H2, same Ar) is accomplished with anhyd. FeCl3 in CH2Cl2. This crude product can be readily metalated to afford II (M = Zn, Pb). The direct fusion of arom. rings to porphyrins occurred without the need to activate porphyrin rings with nickel, or the arom. rings with alkoxy groups. The UV-visible-NIR spectra of I and II (M = H2, Zn, Pb) were studied, and their redox potentials were detd. by cyclic voltammetry. Thin films of II (M = H2, Zn, Pb) contg. different ratios of [6,6]-phenyl-C61-butyric acid Me ester (PCBM) were prepd. and noncovalent interactions between the porphyrins and π-conjugated acceptors were studied by UV-visible-NIR spectroscopy. Pyrene-fused dimers II were used as active materials in NIR photodetectors, and give external quantum efficiencies of ≤ 6.5% at λ = 1350 nm for II (M = Zn). The effect of arom. ring fusion to porphyrin tapes in a (meso,β) mode was also explored by DFT methods for several diporphyrin core systems.
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    Jiao, C.; Huang, K.-W.; Guan, Z.; Xu, Q.-H.; Wu, J. N-Annulated Perylene Fused Porphyrins with Enhanced Near-IR Absorption and Emission. Org. Lett. 2010, 12, 4046– 4049,  DOI: 10.1021/ol1016383
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    N-Annulated Perylene Fused Porphyrins with Enhanced Near-IR Absorption and Emission
    Jiao, Chongjun; Huang, Kuo-Wei; Guan, Zhenping; Xu, Qing-Hua; Wu, Jishan
    Organic Letters (2010), 12 (18), 4046-4049CODEN: ORLEF7; ISSN:1523-7060. (American Chemical Society)
    N-Annulated perylene fused porphyrins 1 and 2 were synthesized by oxidative dehydrogenation using a Sc(OTf)3/DDQ system. These newly synthesized hybrid mols. are highly sol. in org. solvents and exhibit remarkably intense near-IR absorption, as well as detectable photoluminescence quantum yields, all of which are comparable to or even exceed those of either meso-β doubly linked porphyrin dimer/trimer or bis/tri-N-annulated perylenes.
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    Richeter, S.; Jeandon, C.; Kyritsakas, N.; Ruppert, R.; Callot, H. J. Preparation of Six Isomeric Bis-Acylporphyrins with Chromophores Reaching the Near-Infrared via Intramolecular Friedel–Crafts Reaction. J. Org. Chem. 2003, 68, 9200– 9208,  DOI: 10.1021/jo035108m
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    Preparation of Six Isomeric Bis-acylporphyrins with Chromophores Reaching the Near-Infrared via Intramolecular Friedel-Crafts Reaction
    Richeter, Sebastien; Jeandon, Christophe; Kyritsakas, Nathalie; Ruppert, Romain; Callot, Henry J.
    Journal of Organic Chemistry (2003), 68 (24), 9200-9208CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)
    The prepn. of six diketones based on the frameworks of five bis-naphthoporphyrins and one perinaphthoporphyrin is described. All diketones derive from meso-tetraarylporphyrins having incorporated two carbonyl groups, each one connected to one β-pyrrole carbon and one ortho carbon atom from a meso-aryl group. These compds. were all produced in good yield by intramol. Friedel-Crafts acylation, either from porphyrins meso-substituted by o-carboxyphenyl or o,o'-dicarboxyphenyl substituents or from porphyrins bearing carboxy groups attached to the pyrrolic β-positions. Although the former reaction does not show significant regioselectivity when run on nickel complexes, the opposite is true for the corresponding free bases. All diketones show a spectacular bathochromic shift of the UV-vis absorption, the longest wavelength bands absorbing in the 700-825 nm range. Two compds. were structurally characterized by X-ray diffraction. In the case of the diketone, whose carbonyl groups are attached to vicinal pyrrolic β-positions, a significant intermol. interaction between the two carbonyl groups and an arom. hydrogen atom was detected.
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    Saegusa, Y.; Ishizuka, T.; Komamura, K.; Shimizu, S.; Kotani, H.; Kobayashi, N.; Kojima, T. Ring-Fused Porphyrins: Extension of π-Conjugation Significantly Affects the Aromaticity and Optical Properties of the Porphyrin π-Systems and the Lewis Acidity of the Central Metal Ions. Phys. Chem. Chem. Phys. 2015, 17, 15001– 15011,  DOI: 10.1039/C5CP01420D
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    Ring-fused porphyrins: extension of π-conjugation significantly affects the aromaticity and optical properties of the porphyrin π-systems and the Lewis acidity of the central metal ions
    Saegusa, Yuta; Ishizuka, Tomoya; Komamura, Keiyu; Shimizu, Soji; Kotani, Hiroaki; Kobayashi, Nagao; Kojima, Takahiko
    Physical Chemistry Chemical Physics (2015), 17 (22), 15001-15011CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    Here, the authors report the effects of ring fusion, which causes expansion of the π-conjugation circuits of the porphyrin derivs. to the fused meso-aryl groups, on the aromaticity and the magnetic properties of porphyrin derivs. These studies revealed the facts that the ring fusion with five-membered rings causes not only the remarkable red shifts of the absorption bands and narrowed HOMO-LUMO gaps, but also the contribution of anti-arom. resonance forms to the magnetic properties as obsd. in the 1H NMR spectra. The optical absorption and MCD spectroscopies indicate that the increase in the no. of the fused rings causes stabilization of the LUMO level of the porphyrin derivs. and as a result induces the loosening of the LUMO degeneracy that is generally obsd. for porphyrins. The electronic structure of a quadruply fused porphyrin deriv. was exptl. clarified by the ESR studies on the 1e--oxidized and 1e--reduced species in THF. Also, the authors revealed the substituent effects of the fused meso-aryl groups of quadruply fused porphyrins (QFPs) on the crystal structures, absorption spectra and redox potentials; the sensitiveness of the substituent effects shows that the π-conjugation circuits extended to the fused meso-aryl groups. Addnl., the elongation of the bond lengths between the pyrrolic nitrogen and the central metal ions in QFP-metal complexes causes a remarkable increase of the Lewis acidity of the central metal ions.
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    Tokuji, S.; Takahashi, Y.; Shinmori, H.; Shinokubo, H.; Osuka, A. Synthesis of a Pyridine-Fused Porphyrinoid: Oxopyridochlorin. Chem. Commun. 2009, 1028– 1030,  DOI: 10.1039/b819284g
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    Synthesis of a pyridine-fused porphyrinoid: oxopyridochlorin
    Tokuji, Sumito; Takahashi, Yuji; Shinmori, Hideyuki; Shinokubo, Hiroshi; Osuka, Atsuhiro
    Chemical Communications (Cambridge, United Kingdom) (2009), (9), 1028-1030CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    Treatment of 3,5-dibenzoylporphyrins with ammonium acetate provides oxopyridochlorins I [M = H2, Ni, Zn; R = 3,5-(Me3C)2C6H3] as the first examples of pyridine-fused porphyrinoids. I display absorption bands at wavelengths from 400-1000 nm (into the near IR region), with the absorption band for I (M = Ni) increasing significantly in width upon protonation. I (M = H2, Zn) sensitize the formation of singlet oxygen with quantum yields of 0.52-0.79 and do not decomp. under the irradn. conditions. The structures of I·2 MeOH (M = Zn), I·MeOH (M = H2), and I·3 (ClCH2CH2Cl) (M = Ni) are detd. by X-ray crystallog.
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    Lewtak, J. P.; Gryko, D. T. Synthesis of π-Extended Porphyrins via Intramolecular Oxidative Coupling. Chem. Commun. 2012, 48, 10069– 10086,  DOI: 10.1039/c2cc31279d
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    Synthesis of π-extended porphyrins via intramolecular oxidative coupling
    Lewtak, Jan P.; Gryko, Daniel T.
    Chemical Communications (Cambridge, United Kingdom) (2012), 48 (81), 10069-10086CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    A review. Porphyrins fused with other arom. units at the meso- and β-positions have recently emerged as a hot topic of research. Their synthesis typically starts with prepn. of precursors via either Suzuki coupling of a meso-bromoporphyrin or mixed-aldehyde condensation, and is followed by oxidative arom. coupling, often using high-valent metal reagents (DDQ/Sc(OTf)3 and Fe(iii) salts are among the most popular). In recent years, porphyrins were oxidatively coupled not only with well-known arom. hydrocarbons such as naphthalene and pyrene, but also with more complex heterocyclic fragments, including indole, phenanthro[1,10,9,8-cdefg]carbazole and BODIPY. A subtle relationship exists between the output of intramol. oxidative coupling and the nature of the second arom. moiety, cation in the porphyrin cavity, oxidant, and type of remaining meso-substituent. The extension of the porphyrin chromophore leads to significant change in linear and non-linear optical properties. Very strong bathochromic shifts of absorption (λmax reaching 1.5-2 μ in some cases) and increases in two-photon absorption cross-sections are typical for these functional dyes.
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    Moss, A.; Jang, Y.; Arvidson, J.; N Nesterov, V.; D’Souza, F.; Wang, H. Aromatic Heterobicycle-Fused Porphyrins: Impact on Aromaticity and Excited State Electron Transfer Leading to Long-Lived Charge Separation. Chem. Sci. 2022, 13, 9880– 9890,  DOI: 10.1039/D2SC03238D
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    Aromatic heterobicycle-fused porphyrins: impact on aromaticity and excited state electron transfer leading to long-lived charge separation
    Moss, Austen; Jang, Youngwoo; Arvidson, Jacob; Nesterov, Vladimir N.; D'Souza, Francis; Wang, Hong
    Chemical Science (2022), 13 (34), 9880-9890CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
    A new synthetic method to fuse benzo[4,5]imidazo[2,1-a]isoindole to the porphyrin periphery at the β,β-positions has been developed, and its impact on the aromaticity and electronic structures is investigated. Reactivity investigation of the fused benzoimidazo-isoindole component reveals fluorescence quenching of a zinc porphyrin (AMIm-2) upon treatment with a Bronsted acid. The reaction of the zinc porphyrin (AMIm-2) with Me iodide initiated a new org. transformation, resulting in the ring-opening of isoindole with the formation of an aldehyde and dimethylation of the benzoimidazo component. The fused benzoimidazo-isoindole component acted as a good ligand to bind platinum(II), forming novel homobimetallic and heterobimetallic porphyrin complexes. The fusion of benzoimidazo-isoindole on the porphyrin ring resulted in bathochromically shifted absorptions and emissions, reflecting the extended conjugation of the porphyrin π-system. Time-resolved emission and transient absorption spectroscopy revealed stable excited state species of the benzoimidazo-isoindole fused porphyrins. Zinc porphyrin AMIm-2 promoted excited state electron transfer upon coordinating with an electron acceptor, C60, generating a long-lived charge-sepd. state, in the order of 37.4 μs. The formation of the exceptionally long-lived charge-sepd. state is attributed to the involvement of both singlet and triplet excited states of AMIm-2, which is rarely reported in porphyrins.
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    Liu, Z.; Fu, S.; Liu, X.; Narita, A.; Samorì, P.; Bonn, M.; Wang, H. I. Small Size, Big Impact: Recent Progress in Bottom-Up Synthesized Nanographenes for Optoelectronic and Energy Applications. Adv. Sci. 2022, 9, 2106055  DOI: 10.1002/advs.202106055
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    Björk, J.; Hanke, F. Towards Design Rules for Covalent Nanostructures on Metal Surfaces. Chem. - Eur. J. 2014, 20, 928– 934,  DOI: 10.1002/chem.201303559
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    Clair, S.; de Oteyza, D. G. Controlling a Chemical Coupling Reaction on a Surface: Tools and Strategies for On-Surface Synthesis. Chem. Rev. 2019, 119, 4717– 4776,  DOI: 10.1021/acs.chemrev.8b00601
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    Controlling a Chemical Coupling Reaction on a Surface: Tools and Strategies for On-Surface Synthesis
    Clair, Sylvain; de Oteyza, Dimas G.
    Chemical Reviews (Washington, DC, United States) (2019), 119 (7), 4717-4776CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review. On-surface synthesis is appearing as an extremely promising research field aimed at creating new org. materials. A large no. of chem. reactions have been successfully demonstrated to take place directly on surfaces through unusual reaction mechanisms. In some cases the reaction conditions can be properly tuned to steer the formation of the reaction products. It is thus possible to control the initiation step of the reaction and its degree of advancement (the kinetics, the reaction yield); the nature of the reaction products (selectivity control, particularly in the case of competing processes); as well as the structure, position, and orientation of the covalent compds., or the quality of the as-formed networks in terms of order and extension. The aim of our review is thus to provide an extensive description of all tools and strategies reported to date and to put them into perspective. We specifically define the different approaches available and group them into a few general categories. In the last part, we demonstrate the effective maturation of the on-surface synthesis field by reporting systems that are getting closer to application-relevant levels thanks to the use of advanced control strategies.
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    Song, S.; Su, J.; Telychko, M.; Li, J.; Li, G.; Li, Y.; Su, C.; Wu, J.; Lu, J. On-Surface Synthesis of Graphene Nanostructures with π-Magnetism. Chem. Soc. Rev. 2021, 50, 3238– 3262,  DOI: 10.1039/D0CS01060J
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    On-surface synthesis of graphene nanostructures with π-magnetism
    Song, Shaotang; Su, Jie; Telychko, Mykola; Li, Jing; Li, Guangwu; Li, Ying; Su, Chenliang; Wu, Jishan; Lu, Jiong
    Chemical Society Reviews (2021), 50 (5), 3238-3262CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
    A review. Graphene nanostructures (GNs) including graphene nanoribbons and nanoflakes have attracted tremendous interest in the field of chem. and materials science due to their fascinating electronic, optical and magnetic properties. Among them, zigzag-edged GNs (ZGNs) with precisely-tunable π-magnetism hold great potential for applications in spintronics and quantum devices. To improve the stability and processability of ZGNs, substitutional groups are often introduced to protect the reactive edges in org. synthesis, which renders the study of their intrinsic properties difficult. In contrast to the conventional wet-chem. method, on-surface bottom-up synthesis presents a promising approach for the fabrication of both unsubstituted ZGNs and functionalized ZGNs with at. precision via surface-catalyzed transformation of rationally-designed precursors. The structural and spin-polarized electronic properties of these ZGNs can then be characterized with sub-mol. resoln. by means of scanning probe microscopy techniques. This aims to highlight recent advances in the on-surface synthesis and characterization of a diversity of ZGNs with π-magnetism. We also discuss the important role of precursor design and reaction stimuli in the on-surface synthesis of ZGNs and their π-magnetism origin. Finally, we will highlight the existing challenges and future perspective surrounding the synthesis of novel open-shell ZGNs towards next-generation quantum technol.
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    Gaweł, P.; Foroutan-Nejad, C. Carbon Rings Push Limits of Chemical Theories. Nature 2023, 623, 922– 924,  DOI: 10.1038/d41586-023-03575-5
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    Cai, Z.-F.; Chen, T.; Wang, D. Insights into the Polymerization Reactions on Solid Surfaces Provided by Scanning Tunneling Microscopy. J. Phys. Chem. Lett. 2023, 14, 2463– 2472,  DOI: 10.1021/acs.jpclett.2c03943
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    Shen, Q.; Gao, H.-Y.; Fuchs, H. Frontiers of On-Surface Synthesis: From Principles to Applications. Nano Today 2017, 13, 77– 96,  DOI: 10.1016/j.nantod.2017.02.007
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    Frontiers of on-surface synthesis: From principles to applications
    Shen, Qian; Gao, Hong-Ying; Fuchs, Harald
    Nano Today (2017), 13 (), 77-96CODEN: NTAOCG; ISSN:1748-0132. (Elsevier Ltd.)
    On-surface synthesis is the bottom-up construction of covalent bonds between mol. building blocks, which has been greatly developed during the past decade. Dozens of reactions have been successfully realized and scrutinized on various surfaces with the help of surface science techniques combined with theor. calcns. Functional nanoarchitectures such as one-dimensional nanowires, nanoribbons and two-dimensional nanonetworks have been constructed on surfaces and explored in several potential applications. In fact, the generation of multilevel nanostructures will play a key role in future soft nanoscience and technologies due to their emergent properties ranging far beyond those of the individual mols. building them up. In this review, we discuss selected examples of important processes in on-surface synthesis developed in recent years and summarize them under the following aspects: (1) on-surface reactions in a category of different carbon types; (2) techniques applied in on-surface synthesis; (3) on-surface synthesized functional nanostructures; and (4) potential applications of on-surface synthesized nano-materials. The review concludes with a perspective of the future development of on-surface synthesis.
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    Xing, G.-Y.; Zhu, Y.-C.; Li, D.-Y.; Liu, P.-N. On-Surface Cross-Coupling Reactions. J. Phys. Chem. Lett. 2023, 14, 4462– 4470,  DOI: 10.1021/acs.jpclett.3c00344
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    Qin, T.; Wang, T.; Zhu, J. Recent Progress in On-Surface Synthesis of Nanoporous Graphene Materials. Commun. Chem. 2024, 7, 154  DOI: 10.1038/s42004-024-01222-2
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    Sooambar, C.; Troiani, V.; Bruno, C.; Marcaccio, M.; Paolucci, F.; Listorti, A.; Belbakra, A.; Armaroli, N.; Magistrato, A.; Zorzi, R. D.; Geremia, S.; Bonifazi, D. Synthesis, Photophysical, Electrochemical, and Electrochemiluminescent Properties of 5,15-Bis(9-Anthracenyl)Porphyrin Derivatives. Org. Biomol. Chem. 2009, 7, 2402– 2413,  DOI: 10.1039/b820210a
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    Synthesis, photophysical, electrochemical, and electrochemiluminescent properties of 5,15-bis(9-anthracenyl)porphyrin derivatives
    Sooambar, Chloe; Troiani, Vincent; Bruno, Carlo; Marcaccio, Massimo; Paolucci, Francesco; Listorti, Andrea; Belbakra, Abdelhalim; Armaroli, Nicola; Magistrato, Alessandra; De Zorzi, Rita; Geremia, Silvano; Bonifazi, Davide
    Organic & Biomolecular Chemistry (2009), 7 (11), 2402-2413CODEN: OBCRAK; ISSN:1477-0520. (Royal Society of Chemistry)
    Novel 5,15-bis(9-anthracenyl)porphyrin derivs. (I; R = H, C6H4NMe2-4) were synthesized by stepwise Suzuki-type coupling reactions using anthracenyl-boronates bearing various electronically active moieties. Absorption spectra of these porphyrin conjugates reveal some degree of delocalization with the directly linked chromophores, particularly in the case of anthracenyl-porphyrin bearing dimethylanilino moieties at the two extremities. Fluorescence and 77 K phosphorescence properties indicate that the excitation energy is invariably funnelled to the lowest singlet and triplet states of the porphyrin chromophore. The latter levels have been probed also by transient absorption spectroscopy, showing the typical triplet features detected in meso-substituted porphyrins. Extensive electrochem. studies have been performed to unravel the electronic properties of the newly synthesized porphyrins. Low-temp. cyclic voltammetry investigations showed that the anthracenyl-porphyrins are capable of undergoing as many as four electron transfer processes. In particular, by means of UV-Vis-NIR spectroelectrochem. measurements, a NIR-centered intramol. photoinduced intervalence charge transfer (IV-CT) from a neutral N,N-dimethylanilino moiety to the N,N-dimethylanilino radical cation has been obsd. for the doubly-oxidized porphyrin II. The mols. also showed unexpected electrogenerated chemiluminescence properties, which revealed to be largely controlled by the electronic characteristics of the peripheral anthracenyl substituents. The structural and the electronic properties of these complexes have been also characterized by DFT calcns., as well as by X-ray crystallog. analyses.
  49. 49
    Volz, H.; Schäffer, H. Mesosubstituted Porphyrins. III. 5,10,15,20-Tetraanthracenylporphyrin. Chem.-Ztg. 1985, 109, 308– 309
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    Mesosubstituted porphyrins. III. 5,10,15,20-Tetraanthracenylporphyrin
    Volz, Heinrich; Schaeffer, Hermann
    Chemiker-Zeitung (1985), 109 (9), 308-9CODEN: CMKZAT; ISSN:0009-2894.
    The title porphyrin was prepd. in 5.65% overall yield by treating 2-formylpyrrole with 9-lithioanthracene and tetramerizing the resulting carbinol in EtCO2H-PhMe, followed by DDQ oxidn. of residual chlorin in the product.
  50. 50
    Wäckerlin, C. On-Surface Hydrogen/Deuterium Isotope Exchange in Polycyclic Aromatic Hydrocarbons. Angew. Chem. Int. Ed. 2021, 60, 8446– 8449,  DOI: 10.1002/ange.202015552
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    Cai, J.; Ruffieux, P.; Jaafar, R.; Bieri, M.; Braun, T.; Blankenburg, S.; Muoth, M.; Seitsonen, A. P.; Saleh, M.; Feng, X.; Müllen, K.; Fasel, R. Atomically Precise Bottom-up Fabrication of Graphene Nanoribbons. Nature 2010, 466, 470– 473,  DOI: 10.1038/nature09211
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    Atomically precise bottom-up fabrication of graphene nanoribbons
    Cai, Jinming; Ruffieux, Pascal; Jaafar, Rached; Bieri, Marco; Braun, Thomas; Blankenburg, Stephan; Muoth, Matthias; Seitsonen, Ari P.; Saleh, Moussa; Feng, Xinliang; Muellen, Klaus; Fasel, Roman
    Nature (London, United Kingdom) (2010), 466 (7305), 470-473CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)
    Graphene nanoribbons-narrow and straight-edged stripes of graphene, or single-layer graphite-are predicted to exhibit electronic properties that make them attractive for the fabrication of nanoscale electronic devices. In particular, although the two-dimensional parent material graphene exhibits semimetallic behavior, quantum confinement and edge effects should render all graphene nanoribbons with widths smaller than 10 nm semiconducting. But exploring the potential of graphene nanoribbons is hampered by their limited availability: although they were made using chem., sonochem. and lithog. methods as well as through the unzipping of carbon nanotubes, the reliable prodn. of graphene nanoribbons smaller than 10 nm with chem. precision remains a significant challenge. Here the authors report a simple method for the prodn. of atomically precise graphene nanoribbons of different topologies and widths, which uses surface-assisted coupling of mol. precursors into linear polyphenylenes and their subsequent cyclodehydrogenation. The topol., width and edge periphery of the graphene nanoribbon products are defined by the structure of the precursor monomers, which can be designed to give access to a wide range of different graphene nanoribbons. The authors expect that the authors' bottom-up approach to the atomically precise fabrication of graphene nanoribbons will finally enable detailed exptl. studies of the properties of this exciting class of materials. It should even provide a route to graphene nanoribbon structures with engineered chem. and electronic properties, including the theor. predicted intraribbon quantum dots, superlattice structures and magnetic devices based on specific graphene nanoribbon edge states.
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    Mateo, L. M.; Sun, Q.; Liu, S.-X.; Bergkamp, J. J.; Eimre, K.; Pignedoli, C. A.; Ruffieux, P.; Decurtins, S.; Bottari, G.; Fasel, R.; Torres, T. On-Surface Synthesis and Characterization of Triply Fused Porphyrin–Graphene Nanoribbon Hybrids. Angew. Chem., Int. Ed. 2020, 59, 1334– 1339,  DOI: 10.1002/anie.201913024
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    On-Surface Synthesis and Characterization of Triply Fused Porphyrin-Graphene Nanoribbon Hybrids
    Mateo, Luis M.; Sun, Qiang; Liu, Shi-Xia; Bergkamp, Jesse J.; Eimre, Kristjan; Pignedoli, Carlo A.; Ruffieux, Pascal; Decurtins, Silvio; Bottari, Giovanni; Fasel, Roman; Torres, Tomas
    Angewandte Chemie, International Edition (2020), 59 (3), 1334-1339CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    On-surface synthesis offers a versatile approach to prep. novel carbon-based nanostructures that cannot be obtained by conventional soln. chem. Graphene nanoribbons (GNRs) have potential for a variety of applications. A key issue for their application in mol. electronics is in the fine-tuning of their electronic properties through structural modifications, such as heteroatom doping or the incorporation of non-benzenoid rings. In this context, the covalent fusion of GNRs and porphyrins (Pors) is a highly appealing strategy. Herein we present the selective on-surface synthesis of a Por-GNR hybrid, which consists of two Pors connected by a short GNR segment. The atomically precise structure of the Por-GNR hybrid has been characterized by bond-resolved scanning tunneling microscopy (STM) and noncontact at. force microscopy (nc-AFM). The electronic properties have been investigated by scanning tunneling spectroscopy (STS), in combination with DFT calcns., which reveals a low electronic gap of 0.4 eV.
  53. 53
    Kawai, S.; Ishikawa, A.; Ishida, S.; Yamakado, T.; Ma, Y.; Sun, K.; Tateyama, Y.; Pawlak, R.; Meyer, E.; Saito, S.; Osuka, A. On-Surface Synthesis of Porphyrin-Complex Multi-Block Co-Oligomers by Defluorinative Coupling. Angew. Chem., Int. Ed. 2022, 61, e202114697  DOI: 10.1002/anie.202114697
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    On-Surface Synthesis of Porphyrin-Complex Multi-Block Co-Oligomers by Defluorinative Coupling
    Kawai, Shigeki; Ishikawa, Atsushi; Ishida, Shin-ichiro; Yamakado, Takuya; Ma, Yujing; Sun, Kewei; Tateyama, Yoshitaka; Pawlak, Remy; Meyer, Ernst; Saito, Shohei; Osuka, Atsuhiro
    Angewandte Chemie, International Edition (2022), 61 (3), e202114697CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    On-surface chem. reaction has become a very powerful technique to synthesize nanostructures by linking small mols. in the bottom-up approach. Given the fact that most reactants are simultaneously activated at certain temps., a sequential reaction in a controlled way has remained challenging. Here, the authors present an on-surface synthesis of multi-block cooligomers from trifluoromethyl (CF3) substituted porphyrin metal complexes. The oligomerization on Au(111) is demonstrated with a combination of bond-resolved scanning probe microscopy and d. functional theory (DFT) calcns. Even after the first oligomerization of single monomer unit, the termini of the oligomer keep the CF3 group, which can be used as a reactant for further coupling in a sequential order. Consequently, copper, cobalt, and palladium complexes of bisanthracene-fused porphyrin oligomers were linked with each other in a designed order.
  54. 54
    Sen, D.; Błoński, P.; de la Torre, B.; Jelínek, P.; Otyepka, M. Thermally Induced Intra-Molecular Transformation and Metalation of Free-Base Porphyrin on Au(111) Surface Steered by Surface Confinement and Ad-Atoms. Nanoscale Adv. 2020, 2, 2986– 2991,  DOI: 10.1039/D0NA00401D
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    Thermally induced intra-molecular transformation and metalation of free-base porphyrin on Au(111) surface steered by surface confinement and ad-atoms
    Sen, Dipayan; Blonski, Piotr; Torre, Bruno de la; Jelinek, Pavel; Otyepka, Michal
    Nanoscale Advances (2020), 2 (7), 2986-2991CODEN: NAADAI; ISSN:2516-0230. (Royal Society of Chemistry)
    We investigated chem. transformations of a fluorinated free-base porphyrin, 5,10,15,20-tetrakis(4-fluorophenyl)-21,23H-porphyrin (2H-4FTPP) under a Au(111) surface confinement and including gold adatoms by using an expt. and d. functional theory based first-principles calcns. Annealing of 2H-4FTPP led to cyclodehydrogenation of the mol. to a π-extended fused arom. planar compd., 2H-4FPP, and metalation of the porphyrin ring by Au atoms to Au-4FPP complex. Noticeable lowering of bond-dissocn. energies of the pyrrole's C-H bonds of the Au(111) supported mol. with respect to their values in the gas phase explained the obsd. on-surface planarization. Our findings also indicate that Au adatoms may catalyze cleavage of C-H/F bonds in temp.-initiated processes on Au surfaces. BDEs and explicit inclusion of Au adatoms helps to rationalize thermally induced chem. reactions on the resp. surface.
  55. 55
    Lowe, B.; Hellerstedt, J.; Matěj, A.; Mutombo, P.; Kumar, D.; Ondráček, M.; Jelinek, P.; Schiffrin, A. Selective Activation of Aromatic C–H Bonds Catalyzed by Single Gold Atoms at Room Temperature. J. Am. Chem. Soc. 2022, 144, 21389– 21397,  DOI: 10.1021/jacs.2c10154
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    Selective activation of aromatic C-H bonds catalyzed by single gold atoms at room temperature
    Lowe, Benjamin; Hellerstedt, Jack; Matej, Adam; Mutombo, Pingo; Kumar, Dhaneesh; Ondracek, Martin; Jelinek, Pavel; Schiffrin, Agustin
    Journal of the American Chemical Society (2022), 144 (46), 21389-21397CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Selective activation and controlled functionalization of C-H bonds in org. mols. is one of the most desirable processes in synthetic chem. Despite progress in heterogeneous catalysis using metal surfaces, this goal remains challenging due to the stability of C-H bonds and their ubiquity in precursor mols., hampering regioselectivity. Here, we examine the interaction between 9,10-dicyanoanthracene (DCA) mols. and Au adatoms on a Ag(111) surface at room temp. (RT). Characterization via low-temp. scanning tunneling microscopy, spectroscopy, and noncontact at. force microscopy, supported by theor. calcns., revealed the formation of organometallic DCA-Au-DCA dimers, where C atoms at the ends of the anthracene moieties are bonded covalently to single Au atoms. The formation of this organometallic compd. is initiated by a regioselective cleaving of C-H bonds at RT. Hybrid quantum mechanics/mol. mechanics calcns. show that this regioselective C-H bond cleaving is enabled by an intermediate metal-org. complex which significantly reduces the dissocn. barrier of a specific C-H bond. Harnessing the catalytic activity of single metal atoms, this regioselective on-surface C-H activation reaction at RT offers promising routes for future synthesis of functional org. and organometallic materials.
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    Mendieta-Moreno, J. I.; Mallada, B.; de la Torre, B.; Cadart, T.; Kotora, M.; Jelínek, P. Unusual Scaffold Rearrangement in Polyaromatic Hydrocarbons Driven by Concerted Action of Single Gold Atoms on a Gold Surface. Angew. Chem., Int. Ed. 2022, 61, e202208010  DOI: 10.1002/anie.202208010
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    56
    Unusual Scaffold Rearrangement in Polyaromatic Hydrocarbons Driven by Concerted Action of Single Gold Atoms on a Gold Surface
    Mendieta-Moreno, Jesus I.; Mallada, Benjamin; de la Torre, Bruno; Cadart, Timothee; Kotora, Martin; Jelinek, Pavel
    Angewandte Chemie, International Edition (2022), 61 (50), e202208010CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Chem. transformation of polyarom. hydrocarbon (PAH) mols. following different reaction strategies has always been the focus of org. synthesis. In this work, we report the synthesis of a PAH mol., formation of which consists of an unusual C-C bond cleavage accompanied by a complex π-conjugated mol. scaffold rearrangement. We demonstrate that the complex chem. transformation is steered by concerted motion of individual Au0 gold atoms on a supporting Au(111) surface. This observation underpins the importance of single-atom catalysis mediated by adatoms in on-surface synthesis as well as catalytic activity of single Au0 atoms facilitating cleavage of covalent carbon bonds.
  57. 57
    Björk, J.; Sánchez-Sánchez, C.; Chen, Q.; Pignedoli, C. A.; Rosen, J.; Ruffieux, P.; Feng, X.; Narita, A.; Müllen, K.; Fasel, R. The Role of Metal Adatoms in a Surface-Assisted Cyclodehydrogenation Reaction on a Gold Surface. Angew. Chem., Int. Ed. 2022, 61, e202212354  DOI: 10.1002/anie.202212354
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    The Role of Metal Adatoms in a Surface-Assisted Cyclodehydrogenation Reaction on a Gold Surface
    Bjork, Jonas; Sanchez-Sanchez, Carlos; Chen, Qiang; Pignedoli, Carlo A.; Rosen, Johanna; Ruffieux, Pascal; Feng, Xinliang; Narita, Akimitsu; Muellen, Klaus; Fasel, Roman
    Angewandte Chemie, International Edition (2022), 61 (49), e202212354CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Dehydrogenation reactions are key steps in many metal-catalyzed chem. processes and in the on-surface synthesis of atomically precise nanomaterials. The principal role of the metal substrate in these reactions is undisputed, but the role of metal adatoms remains, to a large extent, unanswered, particularly on gold substrates. Here, we discuss their importance by studying the surface-assisted cyclodehydrogenation on Au(111) as an ideal model case. We choose a polymer theor. predicted to give one of two cyclization products depending on the presence or absence of gold adatoms. Scanning probe microscopy expts. observe only the product assocd. with adatoms. We challenge the prevalent understanding of surface-assisted cyclodehydrogenation, unveiling the catalytic role of adatoms and their effect on regioselectivity. The study adds new perspectives to the understanding of metal catalysis and the design of on-surface synthesis protocols for novel carbon nanomaterials.
  58. 58
    Frezza, F.; Matěj, A.; Sánchez-Grande, A.; Carrera, M.; Mutombo, P.; Kumar, M.; Curiel, D.; Jelínek, P. On-Surface Synthesis of a Radical 2D Supramolecular Organic Framework. J. Am. Chem. Soc. 2024, 146, 3531– 3538,  DOI: 10.1021/jacs.3c13702
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    Frampton, E. S.; Edmondson, M.; Judd, C. J.; Duncan, D. A.; Jones, R. G.; Saywell, A. Self-Metalation of Tetraphenyl Porphyrin on Au(111): Structural Characterisation via X-Ray Standing Wave Analysis. Inorg. Chim. Acta 2023, 558, 121718  DOI: 10.1016/j.ica.2023.121718
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    Edmondson, M.; Frampton, E. S.; Judd, C. J.; Champness, N. R.; Jones, R. G.; Saywell, A. Order, Disorder, and Metalation of Tetraphenylporphyrin (2H-TPP) on Au(111). Chem. Commun. 2022, 58, 6247– 6250,  DOI: 10.1039/D2CC00820C
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    Order, disorder, and metalation of tetraphenylporphyrin (2H-TPP) on Au(111)
    Edmondson, Matthew; Frampton, Eleanor S.; Judd, Chris J.; Champness, Neil R.; Jones, Robert G.; Saywell, Alex
    Chemical Communications (Cambridge, United Kingdom) (2022), 58 (42), 6247-6250CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    A thermally induced order-disorder transition of tetraphenylporphyrin (2H-TPP) on Au(111) is characterised by scanning probe microscopy and XPS-based techniques. We obsd. that a transition from an ordered close-packed phase to a disordered diffuse phase is correlated with an on-surface cyclodehydrogenation reaction, and that addnl. heating of this diffuse phase gives rise to a single distinct nitrogen environment indicative of the formation of a Au-TPP species.
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    Kalashnyk, N.; Daher Mansour, M.; Pijeat, J.; Plamont, R.; Bouju, X.; Balaban, T. S.; Campidelli, S.; Masson, L.; Clair, S. Edge-On Self-Assembly of Tetra-Bromoanthracenyl-Porphyrin on Silver Surfaces. J. Phys. Chem. C 2020, 124, 22137– 22142,  DOI: 10.1021/acs.jpcc.0c05908
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    Edge-On Self-Assembly of Tetra-bromoanthracenyl-porphyrin on Silver Surfaces
    Kalashnyk, Nataliya; Daher Mansour, Michel; Pijeat, Joffrey; Plamont, Remi; Bouju, Xavier; Balaban, Teodor Silviu; Campidelli, Stephane; Masson, Laurence; Clair, Sylvain
    Journal of Physical Chemistry C (2020), 124 (40), 22137-22142CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    Mol. self-assembly on surfaces is driven by the range of interactions between the mols. themselves and the substrate. Generally, a face-on structure is favored for arom. mols. lying flat on the surface. Here, we report on the supramol. self-assembly of 5,10,15,20-tetrakis(10-bromoanthracen-9-yl)porphyrin on the Ag(111) and Ag(110) surfaces. Well-ordered mol. chains were obsd. by room-temp. scanning tunneling microscopy on both surfaces. The relatively small size of the unit cell revealed an edge-on configuration of the porphyrin macrocycles, i.e., perpendicular to the surface plane, as confirmed by mol. mechanics calcns. Distinct intermol. interactions were found on the two surfaces, providing different mol. chain orientations on Ag(111) and Ag(110).
  62. 62
    Mishra, S.; Yao, X.; Chen, Q.; Eimre, K.; Gröning, O.; Ortiz, R.; Di Giovannantonio, M.; Sancho-García, J. C.; Fernández-Rossier, J.; Pignedoli, C. A.; Müllen, K.; Ruffieux, P.; Narita, A.; Fasel, R. Large Magnetic Exchange Coupling in Rhombus-Shaped Nanographenes with Zigzag Periphery. Nat. Chem. 2021, 13, 581– 586,  DOI: 10.1038/s41557-021-00678-2
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    Large magnetic exchange coupling in rhombus-shaped nanographenes with zigzag periphery
    Mishra, Shantanu; Yao, Xuelin; Chen, Qiang; Eimre, Kristjan; Groning, Oliver; Ortiz, Ricardo; Di Giovannantonio, Marco; Sancho-Garcia, Juan Carlos; Fernandez-Rossier, Joaquin; Pignedoli, Carlo A.; Mullen, Klaus; Ruffieux, Pascal; Narita, Akimitsu; Fasel, Roman
    Nature Chemistry (2021), 13 (6), 581-586CODEN: NCAHBB; ISSN:1755-4330. (Nature Portfolio)
    Nanographenes with zigzag edges are predicted to manifest non-trivial π-magnetism resulting from the interplay of concurrent electronic effects, such as hybridization of localized frontier states and Coulomb repulsion between valence electrons. This provides a chem. tunable platform to explore quantum magnetism at the nanoscale and opens avenues towards org. spintronics. The magnetic stability in nanographenes is thus far greatly limited by the weak magnetic exchange coupling, which remains below the room-temp. thermal energy. Here, we report the synthesis of large rhombus-shaped nanographenes with zigzag peripheries on gold and copper surfaces. Single-mol. scanning probe measurements show an emergent magnetic spin singlet ground state with increasing nanographene size. The magnetic exchange coupling in the largest nanographene (C70H22, contg. five benzenoid rings along each edge), detd. by inelastic electron tunnelling spectroscopy, exceeds 100 meV or 1,160 K, which outclasses most inorg. nanomaterials and survives on a metal electrode.
  63. 63
    Stöckl, Q. S.; Hsieh, Y.-C.; Mairena, A.; Wu, Y.-T.; Ernst, K.-H. Aggregation of C70-Fragment Buckybowls on Surfaces: π–H and π–π Bonding in Bowl Up-Side-Down Ensembles. J. Am. Chem. Soc. 2016, 138, 6111– 6114,  DOI: 10.1021/jacs.6b02412
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    Aggregation of C70-Fragment Buckybowls on Surfaces: π-H and π-π Bonding in Bowl Up-Side-Down Ensembles
    Stockl, Quirin S.; Hsieh, Ya-Chu; Mairena, Anais; Wu, Yao-Ting; Ernst, Karl-Heinz
    Journal of the American Chemical Society (2016), 138 (19), 6111-6114CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    The self-assembly of the C38H14-buckybowl, a fragment bowl of the C70 fullerene, has been studied with scanning tunneling microscopy on the Cu(111) surface. Isolated mols. adsorb bowl opening-up with the center C6 ring parallel to the surface. In extended 2D islands, however, 1/3 of the mols. are oriented such that the bowl opening points down. From a detailed anal. of relative orientation of the mols., the nature of intermol. lateral interactions is identified. In densely packed islands, π-π bonding between convex sides of the bowls dominate, while π-H bonding between rim and convex sides plays the important role in small mol. 2D clusters.
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    Wang, T.; Zhu, J. Confined On-Surface Organic Synthesis: Strategies and Mechanisms. Surf. Sci. Rep. 2019, 74, 97– 140,  DOI: 10.1016/j.surfrep.2019.05.001
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    Confined on-surface organic synthesis: Strategies and mechanisms
    Wang, Tao; Zhu, Junfa
    Surface Science Reports (2019), 74 (2), 97-140CODEN: SSREDI; ISSN:0167-5729. (Elsevier B.V.)
    A review. On-surface synthesis has been one of the hottest research fields in surface science in the last decade, owing to its great potential for bottom-up synthesis of functional mols. and covalent nanomaterials. Compared to classical in-soln. chem., all of the on-surface reactions are done without solvent, thus very minimal byproducts and no limitation of soly. are involved. However, because of its typically required ultra-high vacuum conditions, where only limited catalysts can be used, a key challenge for on-surface synthesis is the precise control of the reaction pathway. Countless efforts have been made for controllable synthesis of target chem. structures on surfaces by distinct strategies. These strategies can be summarized under following aspects: (1) rational choice of surfaces; (2) template effects based on two-dimensional (2D) environments; (3) on-surface thermodn. and kinetic controls; (4) the participation of chemisorbed nonmetal adatoms on surfaces. This report reviews the recent progress toward the control of on-surface synthesis and raises a series of questions at the end, which deserve further explorations in the future.
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  1. Lili Deng, Qian Su, Zengxi Li, Weiguo Cheng. Flexible chain tunning of metalloporphyrin ionic framework: Spatial microenvironment construction for enhancing urea alcoholysis. Applied Materials Today 2025, 42 , 102596. https://doi.org/10.1016/j.apmt.2025.102596
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  • Abstract

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    Scheme 1

    Scheme 1. Comparison of Solution and On-Surface Synthesis of Fused Anthracenyl Porphyrins
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    Figure 1

    Figure 1. ToF-SIM spectra tracking mass loss due to cyclodehydrogenation of Zn-anthracenyl porphyrins upon thermal activation. (a) Temperature series of ZnBAP on Au(111) leading to ZnBAP-8H and ZnBAP-12H products upon annealing to 458 and 603 K, respectively. Colored bars above the spectra represent expected mass distributions of C60H36N4Zn+ (ZnBAP), C60H28N4Zn+ (ZnBAP-8H), and C60H24N4Zn+ (ZnBAP-12H) ions. (b) ToF-SIMS temperature series of ZnTAP on Au(111) showing masses corresponding to ZnTAP, ZnTAP-16H, and ZnTAP-20H. Simulated mass distributions thereof are shown in the spectra.

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    Figure 2

    Figure 2. STM identification of native and cyclodehydrogenated ZnBAP molecular species. (a) Overview STM image (25 × 25 nm2) of native ZnBAP molecules on Au(111) assembled into braid-like structures. (b) Close-up STM image (5 × 5 nm2) from (a) overlaid with ball-and-stick molecular models. (c) Simulated unoccupied state density maps of ZnBAP molecules as arranged in (b). (d) Overview STM image (30 × 30 nm2) of ZnBAP-8H molecules on Au(111) obtained after being annealed to 468 K. (e) Close-up STM image (5 × 5 nm2) of three ZnBAP-8H molecules overlaid with molecular models. (f) Simulated occupied state density maps of ZnBAP-8H molecules from (e). (g) Overview STM image (30 × 30 nm2) of ZnBAP-12H molecules on Au(111) obtained after annealing to 603 K. The molecules encircled in blue appear much brighter due to transmetalation of Zn with Au. (h) Close-up STM image (5 × 5 nm2) of two ZnBAP-12H molecules overlaid with the molecular models. (i) Simulated occupied state density maps of anti- and syn-ZnBAP-12H molecules from (h).

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    Figure 3

    Figure 3. STM identification of native and cyclodehydrogenated ZnTAP molecular species. (a) Overview STM image (15 × 15 nm2) of native ZnTAP molecules self-assembled on Au(111). The image is superimposed with ball-and-stick molecular models. (b) Ball-and-stick molecular model of the molecular assembly from (a), together with simulated unoccupied state density maps of ZnTAP molecules as arranged in the model. (c) Overview STM image (30 × 30 nm2) of ZnTAP-16H molecules imaged after annealing to 483 K. Molecules are encircled depending on the conformation with the color code from (d). Gray encircled molecules appear as if they are missing one anthracenyl unit, an impurity from the synthesis or fragmentation during the sublimation. (d) Simulated occupied state density maps of six possible conformations of ZnTAP-16H molecules. The labeling of the conformers is performed starting from the upper left corner. (e) Overview STM image (20 × 20 nm2) of ZnTAP-20H molecules imaged after annealing to 613 K. The inset represents simulated unoccupied state density map of an adatom-coordinated structure. (f) Overview (50 × 50 nm2) and (g, h) close-up (15 × 15 nm2) STM images obtained after annealing to 653 K. ZnTAP-20H molecules form different size oligomers via intermolecular C–C coupling. (i) Overview STM image (50 × 33.2 nm2) of a sample with very high molecular coverage obtained after annealing to 653 K with molecules appearing as up/down bowls. (j) Simulated unoccupied state density maps of ZnTAP-24H molecules appearing as up/down bowls and ZnTAP-22H molecules with the Au adatom.

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    Figure 4

    Figure 4. Temperature-dependent Zn 2p and N 1s XP spectra of ZnBAP/ZnTAP on Au(111). (a) Zn 2p and N 1s XP spectra obtained upon deposition and annealing of ZnBAP molecules on the Au(111) substrate. (b) Zn 2p and N 1s XP spectra obtained upon deposition and annealing of ZnTAP molecules on the Au(111) substrate. Significant reduction of all XPS signals was observed at the first annealing step due to molecular desorption. Additional molecular deposition was therefore performed while keeping the substrate at 473 K.

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      Bioinspired Applications of Porphyrin Derivatives
      Park, Jong Min; Hong, Kyeong-Im; Lee, Hosoowi; Jang, Woo-Dong
      Accounts of Chemical Research (2021), 54 (9), 2249-2260CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
      Conspectus: Porphyrin derivs. are ubiquitous in nature and have important biol. roles, such as in light harvesting, oxygen transport, and catalysis. Owing to their intrinsic π-conjugated structure, porphyrin derivs. exhibit characteristic photophys. and electrochem. properties. In biol. systems, porphyrin derivs. are assocd. with various protein mols. through noncovalent interactions. For example, Hb, which is responsible for oxygen transport in most vertebrates, consists of four subunits of a globular protein with an iron porphyrin deriv. prosthetic group. Furthermore, noncovalently arranged porphyrin derivs. are the fundamental chromophores in light-harvesting systems for photosynthesis in plants and algae. These biol. important roles originate from the functional versatility of porphyrin derivs. Specifically, porphyrins are excellent host compds., forming coordination complexes with various metal ions that adds functionality to the porphyrin unit, such as redox activity and addnl. ligand binding at the central metal ion. In addn., porphyrins are useful building blocks for functional supramol. assemblies because of their flat and sym. mol. architectures, and their excellent photophys. properties are typically utilized for the fabrication of bioactive functional materials. In this Account, we summarize our endeavors over the past decade to develop functional materials based on porphyrin derivs. using bioinspired approaches. In the first section, we discuss several synthetic receptors that act as artificial allosteric host systems and can be used for the selective detection of various chems., such as cyanide, chloride, and amino acids. In the second section, we introduce multiporphyrin arrays as mimics of natural light-harvesting complexes. The active control of energy transfer processes by addnl. guest binding and the fabrication of org. photovoltaic devices using porphyrin derivs. are also introduced. In the third section, we introduce several types of porphyrin-based supramol. assemblies. Through noncovalent interactions such as metal-ligand interaction, hydrogen bonding, and π-π interaction, porphyrin derivs. were constructed as supramol. polymers with formation of fiber or toroidal assembly. In the last section, the application of porphyrin derivs. for biomedical nanodevice fabrication is introduced. Even though porphyrins were good candidates as photosensitizers for photodynamic therapy, they have limitations for biomedical application owing to aggregation in aq. media. We suggested ionic dendrimer porphyrins and they showed excellent photodynamic therapy (PDT) efficacy.
    10. 10
      Lindsey, J. S.; Prathapan, S.; Johnson, T. E.; Wagner, R. W. Porphyrin Building Blocks for Modular Construction of Bioorganic Model Systems. Tetrahedron 1994, 50, 8941– 8968,  DOI: 10.1016/S0040-4020(01)85364-3
      10
      Porphyrin building blocks for modular construction of bioorganic model systems
      Lindsey, Jonathan S.; Prathapan, Sreedharan; Johnson, Thomas E.; Wagner, Richard W.
      Tetrahedron (1994), 50 (30), 8941-68CODEN: TETRAB; ISSN:0040-4020.
      The authors outline a modular building block strategy for the covalent assembly of porphyrin-contg. model systems. Mol. design issues for the synthesis of porphyrin dimers, dye-porphyrin dyads, and multi-porphyrin arrays have been used to guide the development of this approach. The major design constraints are to achieve directed coupling of free base and/or metalloporphyrin building blocks in dil. soln. under non-acidic non-metalating conditions. A set of 24 porphyrin building blocks has been synthesized. The porphyrins are prepd. by reaction of substituted benzaldehydes with pyrrole using the two-step one-flask room temp. porphyrin synthesis. Routes to 7 substituted aldehydes are described. Each porphyrin bears one or four functional groups, and many also are facially-encumbered in order to achieve increased soly. Twelve functional groups that meet the design criteria include those that can be reacted directly in coupling reactions such as active esters, α-chloroacetamido, benzoyl, and iodo groups, and others that require deprotection prior to coupling, such as phthalimidomethyl, FMOC-prolyl, trimethylsilylethynyl, dithiolane, methoxycarbonyl, and trimethylsilylethoxycarbonyl groups. The synthesis of 13 porphyrin dimers and dye-porphyrin dyads has been explored as a testbed for refining strategies for the synthesis of mol. devices contg. multiple porphyrins and other components. The coupling strategies investigated have yielded dimers or dyads with subunits linked by amide, butadiyne, ethyne, or thiourea groups. This building block approach should enable rapid assembly of architecturally-defined porphyrin-based model systems.
    11. 11
      Auwärter, W.; Écija, D.; Klappenberger, F.; Barth, J. V. Porphyrins at Interfaces. Nat. Chem. 2015, 7, 105– 120,  DOI: 10.1038/nchem.2159
      11
      Porphyrins at interfaces
      Auwarter Willi; Klappenberger Florian; Barth Johannes V; Ecija David
      Nature chemistry (2015), 7 (2), 105-20 ISSN:.
      Porphyrins and other tetrapyrrole macrocycles possess an impressive variety of functional properties that have been exploited in natural and artificial systems. Different metal centres incorporated within the tetradentate ligand are key for achieving and regulating vital processes, including reversible axial ligation of adducts, electron transfer, light-harvesting and catalytic transformations. Tailored substituents optimize their performance, dictating their arrangement in specific environments and mediating the assembly of molecular nanoarchitectures. Here we review the current understanding of these species at well-defined interfaces, disclosing exquisite insights into their structural and chemical properties, and also discussing methods by which to manipulate their intramolecular and organizational features. The distinct characteristics arising from the interfacial confinement offer intriguing prospects for molecular science and advanced materials. We assess the role of surface interactions with respect to electronic and physicochemical characteristics, and describe in situ metallation pathways, molecular magnetism, rotation and switching. The engineering of nanostructures, organized layers, interfacial hybrid and bio-inspired systems is also addressed.
    12. 12
      Gottfried, J. M. Surface Chemistry of Porphyrins and Phthalocyanines. Surf. Sci. Rep. 2015, 70, 259– 379,  DOI: 10.1016/j.surfrep.2015.04.001
      12
      Surface chemistry of porphyrins and phthalocyanines
      Gottfried, J. Michael
      Surface Science Reports (2015), 70 (3), 259-379CODEN: SSREDI; ISSN:0167-5729. (Elsevier B.V.)
      This review covers the surface chem. of porphyrins, phthalocyanines, their metal complexes, and related compds., with particular focus on chem. reactions at solid/vacuum interfaces. Porphyrins are not only important biomols., they also find, together with the artificial phthalocyanines, numerous technol. and scientific applications, which often involve surface and interface related aspects. After a brief summary of fundamental properties of these mols. in the context of surface science, the following topics will be discussed: (1) Aspects of geometric structure, including self-assembly, conformation, mobility and manipulation of the adsorbed mols. (2) Surface-related changes of the electronic structure and the magnetic properties. (3) The role of the metal center in the surface chem. bond. (4) On-surface coordination reactions, such as direct metalation and coordination of axial ligands. (5) The influence of axial ligands on the surface chem. bond and the magnetic properties.
    13. 13
      Sun, Q.; Mateo, L. M.; Robles, R.; Ruffieux, P.; Lorente, N.; Bottari, G.; Torres, T.; Fasel, R. Inducing Open-Shell Character in Porphyrins through Surface-Assisted Phenalenyl π-Extension. J. Am. Chem. Soc. 2020, 142, 18109– 18117,  DOI: 10.1021/jacs.0c07781
      13
      Inducing Open-Shell Character in Porphyrins through Surface-Assisted Phenalenyl π-Extension
      Sun, Qiang; Mateo, Luis M.; Robles, Roberto; Ruffieux, Pascal; Lorente, Nicolas; Bottari, Giovanni; Torres, Tomas; Fasel, Roman
      Journal of the American Chemical Society (2020), 142 (42), 18109-18117CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Org. open-shell compds. are extraordinarily attractive materials for their use in mol. spintronics thanks to their long spin-relaxation times and structural flexibility. Porphyrins (Pors) have widely been used as mol. platforms to craft persistent open-shell structures through soln.-based redox chem. However, very few examples of inherently open-shell Pors have been reported, which are typically obtained through the fusion of non-Kekul´e polyarom. hydrocarbon moieties to the Por core. The inherent instability and low soly. of these radical species, however, requires the use of bulky substituents and multistep synthetic approaches. On-surface synthesis has emerged as a powerful tool to overcome such limitations, giving access to structures that cannot be obtained through classical methods. Herein, we present a simple and straightforward method for the on-surface synthesis of phenalenyl-fused Pors using readily available mol. precursors. In a systematic study, we examine the structural and electronic properties of three surface-supported Pors, bearing zero, two (PorA2), and four (PorA4) meso-fused phenalenyl moieties. Through atomically resolved real-space imaging by scanning probe microscopy and high-resoln. scanning tunneling spectroscopy combined with d. functional theory calcns., we unambiguously demonstrate a triplet ground state for PorA2 and a charge-transfer-induced open-shell character for the intrinsically closed-shell PorA4.
    14. 14
      Sun, Q.; Mateo, L. M.; Robles, R.; Ruffieux, P.; Bottari, G.; Torres, T.; Fasel, R.; Lorente, N. Magnetic Interplay between π-Electrons of Open-Shell Porphyrins and d-Electrons of Their Central Transition Metal Ions. Adv. Sci. 2022, 9, 2105906  DOI: 10.1002/advs.202105906
      14
      Magnetic Interplay between p-Electrons of Open-Shell Porphyrins and d-Electrons of Their Central Transition Metal Ions
      Sun, Qiang; Mateo, Luis M.; Robles, Roberto; Ruffieux, Pascal; Bottari, Giovanni; Torres, Tomas; Fasel, Roman; Lorente, Nicolas
      Advanced Science (Weinheim, Germany) (2022), 9 (19), 2105906CODEN: ASDCCF; ISSN:2198-3844. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Magnetism is typically assocd. with d- or f-block elements, but can also appear in org. mols. with unpaired p-electrons. This has considerably boosted the interest in such org. materials with large potential for spintronics and quantum applications. While several materials showing either d/f or p-electron magnetism have been synthesized, the combination of both features within the same structure has only scarcely been reported. Open-shell porphyrins (Pors) incorporating d-block transition metal ions represent an ideal platform for the realization of such architectures. Herein, the prepn. of a series of open-shell, p-extended Pors that contain magnetically active metal ions (i.e., CuII, CoII, and FeII) through a combination of in-soln. and on-surface synthesis is reported. A detailed study of the magnetic interplay between p- and d-electrons in these metalloPors has been performed by scanning probe methods and d. functional theory calcns. For the Cu and FePors, ferromagnetically coupled p-electrons are detd. to be delocalized over the Por edges. For the CoPor, the authors find a Kondo resonance resulting from the singly occupied CoIIdz2 orbital to dominate the magnetic fingerprint. The Fe deriv. exhibits the highest magnetization of 3.67μB (S≈2) and an exchange coupling of 16 meV between the p-electrons and the Fe d-states.
    15. 15
      Baklanov, A.; Garnica, M.; Robert, A.; Bocquet, M.-L.; Seufert, K.; Küchle, J. T.; Ryan, P. T. P.; Haag, F.; Kakavandi, R.; Allegretti, F.; Auwärter, W. On-Surface Synthesis of Nonmetal Porphyrins. J. Am. Chem. Soc. 2020, 142, 1871– 1881,  DOI: 10.1021/jacs.9b10711
      15
      On-Surface Synthesis of Nonmetal Porphyrins
      Baklanov, Aleksandr; Garnica, Manuela; Robert, Anton; Bocquet, Marie-Laure; Seufert, Knud; Kuechle, Johannes T.; Ryan, Paul T. P.; Haag, Felix; Kakavandi, Reza; Allegretti, Francesco; Auwaerter, Willi
      Journal of the American Chemical Society (2020), 142 (4), 1871-1881CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      We report the on-surface synthesis of a nonmetal porphyrin, namely, silicon tetraphenylporphyrin (Si-TPP), by the deposition of at. silicon onto a free-base TPP layer on a Ag(100) surface under ultrahigh vacuum (UHV) conditions. Scanning tunneling microscopy provides insights into the self-assembly of the TPP mols. before and after Si insertion. Silicon coordinates with all four nitrogen atoms of the TPP macrocycle and interacts with a silver atom of the substrate as confirmed by scanning tunneling spectroscopy, XPS, and complementary d. functional theory calcns. The Si-TPP complex presents a saddle-shaped conformation that is stable under STM manipulation. Our study shows how protocols established for the on-surface metalation of tetrapyrroles can be adopted to achieve nonmetal porphyrins. Complementary expts. yielding Si-TPP and Ge-TPP on Ag(111) highlight the applicability to different main group elements and supports. The success of our nonmetal porphyrin synthesis procedure is further corroborated by a temp.-programmed desorption expt., revealing the desorption of Ge-TPP. This extension of interfacial complex formation beyond metal elements opens promising prospects for new tetrapyrrole architectures with distinct properties and functionalities.
    16. 16
      Chen, H.; Tao, L.; Wang, D.; Wu, Z.-Y.; Zhang, J.-L.; Gao, S.; Xiao, W.; Du, S.; Ernst, K.-H.; Gao, H.-J. Stereoselective On-Surface Cyclodehydrofluorization of a Tetraphenylporphyrin and Homochiral Self-Assembly. Angew. Chem., Int. Ed. 2020, 59, 17413– 17416,  DOI: 10.1002/anie.202005425
      16
      Stereoselective On-Surface Cyclodehydrofluorization of a Tetraphenylporphyrin and Homochiral Self-Assembly
      Chen, Hui; Tao, Lei; Wang, Dongfei; Wu, Zhuo-Yan; Zhang, Jun-Long; Gao, Song; Xiao, Wende; Du, Shixuan; Ernst, Karl-Heinz; Gao, Hong-Jun
      Angewandte Chemie, International Edition (2020), 59 (40), 17413-17416CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The thermally induced cyclodehydrofluorization of iron tetrakis(pentafluorophenyl)porphyrin proceeded highly stereoselectively to give a prochiral product on a gold surface in an ultrahigh vacuum, whereas dehydrocyclization of the resp. iron tetrakisphenylporphyrin did not show such selectivity. Stereoselectivity was predominantly obsd. for closely packed layers, which is an indication of intermol. cooperativity and steric constraints induced by adjacent species. D. functional theory identified intermol. packing constraints as the origin of such selectivity during the reaction. Scanning tunneling microscopy revealed the formation of an enantiomerically pure two-dimensional self-assembly as a conglomerate of mirror domains. On-surface two-dimensional topochem., as reported herein, may open new routes for stereoselective synthesis.
    17. 17
      Zhao, Y.; Jiang, K.; Li, C.; Liu, Y.; Xu, C.; Zheng, W.; Guan, D.; Li, Y.; Zheng, H.; Liu, C.; Luo, W.; Jia, J.; Zhuang, X.; Wang, S. Precise Control of π-Electron Magnetism in Metal-Free Porphyrins. J. Am. Chem. Soc. 2020, 142, 18532– 18540,  DOI: 10.1021/jacs.0c07791
      17
      Precise Control of π-Electron Magnetism in Metal-Free Porphyrins
      Zhao, Yan; Jiang, Kaiyue; Li, Can; Liu, Yufeng; Xu, Chengyang; Zheng, Wenna; Guan, Dandan; Li, Yaoyi; Zheng, Hao; Liu, Canhua; Luo, Weidong; Jia, Jinfeng; Zhuang, Xiaodong; Wang, Shiyong
      Journal of the American Chemical Society (2020), 142 (43), 18532-18540CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      The porphyrin macrocycle can stabilize a set of magnetic metal ions, thus introducing localized net spins near the center. However, it remains elusive but most desirable to introduce delocalized spins in porphyrins with wide implications, for example, for building correlated quantum spins. Here, we demonstrate that metal-free porphyrins host delocalized π-electron magnetism, as revealed by scanning probe microscopy and a different level of theory calcns. Our results demonstrate that engineering of π-electron topologies introduces a spin-polarized singlet state and delocalized net spins in metal-free porphyrins. In addn., the π-electron magnetism can be switched on/off via scanning tunneling microscope manipulation by tuning the interfacial charge transfer. Our results provide an effective way to precisely control the π-electron magnetism in metal-free porphyrins, which can be further extended to design new magnetic functionalities of porphyrin-based architectures.
    18. 18
      Rascon, E. C.; Riss, A.; Matěj, A.; Wiengarten, A.; Mutombo, P.; Soler, D.; Jelinek, P.; Auwärter, W. On-Surface Synthesis of Square-Type Porphyrin Tetramers with Central Antiaromatic Cyclooctatetraene Moiety. J. Am. Chem. Soc. 2023, 145, 967– 977,  DOI: 10.1021/jacs.2c10088
      18
      On-Surface Synthesis of Square-Type Porphyrin Tetramers with Central Antiaromatic Cyclooctatetraene Moiety
      Rascon, Eduardo Corral; Riss, Alexander; Matej, Adam; Wiengarten, Alissa; Mutombo, Pingo; Soler, Diego; Jelinek, Pavel; Auwaerter, Willi
      Journal of the American Chemical Society (2023), 145 (2), 967-977CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      The synthesis of two-dimensionally extended polycyclic heteroat. mols. keeps attracting considerable attention. In particular, frameworks bearing planar cyclooctatetraenes (COT) moieties can display intriguing properties, including antiaromaticity. Here, the authors present an on-surface chem. route to square-type porphyrin tetramers with a central COT ring, coexisting with other oligomers. This approach employing temp.-induced dehydrogenative porphyrin homocoupling in an ultrahigh vacuum environment provides access to surface-supported, unsubstituted porphyrin tetramers that are not easily achievable by conventional synthesis means. Specifically, monomeric free-base (2H-P) and Zn-metalated (Zn-P) porphines (P) were employed to form square-type free-base and Zn-functionalized tetramers on Ag(100). An at.-level characterization by bond-resolved at. force microscopy and scanning tunneling microscopy and spectroscopy is provided, identifying the mol. structures. Complemented by d. functional theory modeling, the electronic structure is elucidated, indeed revealing antiaromaticity induced by the COT moiety. The present study thus gives access, and insights, to a porphyrin oligomer, representing both a model system for directly fused porphyrins and a potential building block for conjugated, extended two-dimensional porphyrin sheets.
    19. 19
      Otsuki, J. STM Studies on Porphyrins. Coord. Chem. Rev. 2010, 254, 2311– 2341,  DOI: 10.1016/j.ccr.2009.12.038
      19
      STM studies on porphyrins
      Otsuki, Joe
      Coordination Chemistry Reviews (2010), 254 (19-20), 2311-2341CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
      A review. Porphyrins are promising components to be used in mol. electronics due to their rich electronic/photonic properties. Prepn. of supramol. architectures of porphyrins on solid surfaces would constitute a basis for further development toward mol. circuitry or other constructs for mol. electronics applications. Assemblies on surfaces can be probed with scanning tunneling microscopy (STM) at submol. resolns. to reveal the arrangements and conformations of mols. on an individual mol. basis. The electronic characteristics within a single porphyrin mol. can also be probed by means of the same technique. This review summarizes the status quo of STM studies on porphyrins on surfaces with regard to their assemblies, structures, and electronic properties at the single mol. level.
    20. 20
      Zhang, Y.; Lu, J.; Zhou, H.; Zhang, G.; Ruan, Z.; Zhang, Y.; Zhang, H.; Sun, S.; Niu, G.; Fu, B.; Yang, B.; Chen, L.; Gao, L.; Cai, J. Highly Regioselective Cyclodehydrogenation of Diphenylporphyrin on Metal Surfaces. ACS Nano 2023, 17, 13575– 13583,  DOI: 10.1021/acsnano.3c02204
      There is no corresponding record for this reference.
    21. 21
      Wu, F.; Zhan, S.; Yang, L.; Zhuo, Z.; Wang, X.; Li, X.; Luo, Y.; Jiang, J. Spatial Confinement of a Carbon Nanocone for an Efficient Oxygen Evolution Reaction. J. Phys. Chem. Lett. 2021, 12, 2252– 2258,  DOI: 10.1021/acs.jpclett.1c00267
      21
      Spatial Confinement of a Carbon Nanocone for an Efficient Oxygen Evolution Reaction
      Wu, Fan; Zhan, Shaoqi; Yang, Li; Zhuo, Zhiwen; Wang, Xijun; Li, Xiyu; Luo, Yi; Jiang, Jun
      Journal of Physical Chemistry Letters (2021), 12 (9), 2252-2258CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      A major bottleneck of large-scale water splitting for hydrogen prodn. is the lack of catalysts for the oxygen evolution reaction (OER) with low cost and high efficiency. In this work, we proposed an electrocatalyst of a curved carbon nanocone embedded with two TMN4 active sites (TM = transition metal) and used first-principles calcns. to investigate their OER mechanisms and catalytic activities. In the particular spatial confinement of a curved nanocone, we found that the distance between intermediates adsorbed on two active sites is shorter than the distance between these two active sites. This finding can be used to enhance OER activity by distance-dependent interaction between intermediates through two different mechanisms. The first mechanism in which an O2 mol. is generated from two neighboring *O intermediates exhibits a linear activity trend, and the lowest overpotential is 0.27 V for the FeN4 system. In the second mechanism, selective stabilization of the *OOH intermediate is realized, leading to a new scaling relationship (ΔG*OOH = ΔG*OH + 3.04 eV) assocd. with a modified OER activity volcano (theor. volcano apex at 0.29 V). The studied mechanisms of the spatial confinement of a carbon nanocone provide a new perspective for designing efficient OER catalysts.
    22. 22
      Hiroto, S.; Miyake, Y.; Shinokubo, H. Synthesis and Functionalization of Porphyrins through Organometallic Methodologies. Chem. Rev. 2017, 117, 2910– 3043,  DOI: 10.1021/acs.chemrev.6b00427
      22
      Synthesis and Functionalization of Porphyrins through Organometallic Methodologies
      Hiroto, Satoru; Miyake, Yoshihiro; Shinokubo, Hiroshi
      Chemical Reviews (Washington, DC, United States) (2017), 117 (4), 2910-3043CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      This review focuses on the postfunctionalization of porphyrins and related compds. through catalytic and stoichiometric organometallic methodologies. The employment of organometallic reactions has become common in porphyrin synthesis. Palladium-catalyzed cross-coupling reactions are now std. techniques for constructing carbon-carbon bonds in porphyrin synthesis. In addn., iridium- or palladium-catalyzed direct C-H functionalization of porphyrins is emerging as an efficient way to install various substituents onto porphyrins. Furthermore, the copper-mediated Huisgen cycloaddn. reaction has become a frequent strategy to incorporate porphyrin units into functional mols. The use of these organometallic techniques, along with the traditional porphyrin synthesis, now allows chemists to construct a wide range of highly elaborated and complex porphyrin architectures.
    23. 23
      Mandal, A. K.; Taniguchi, M.; Diers, J. R.; Niedzwiedzki, D. M.; Kirmaier, C.; Lindsey, J. S.; Bocian, D. F.; Holten, D. Photophysical Properties and Electronic Structure of Porphyrins Bearing Zero to Four Meso-Phenyl Substituents: New Insights into Seemingly Well Understood Tetrapyrroles. J. Phys. Chem. A 2016, 120, 9719– 9731,  DOI: 10.1021/acs.jpca.6b09483
      23
      Photophysical Properties and Electronic Structure of Porphyrins Bearing Zero to Four meso-Phenyl Substituents: New Insights into Seemingly Well Understood Tetrapyrroles
      Mandal, Amit Kumar; Taniguchi, Masahiko; Diers, James R.; Niedzwiedzki, Dariusz M.; Kirmaier, Christine; Lindsey, Jonathan S.; Bocian, David F.; Holten, Dewey
      Journal of Physical Chemistry A (2016), 120 (49), 9719-9731CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
      Six free base porphyrins bearing 0-4 meso substituents have been examd. by steady-state and time-resolved absorption and fluorescence spectroscopy in both toluene and N,N-dimethylformamide (DMF). The lifetime of the lowest singlet excited state (S1) decreases with an increase in the no. of meso-Ph groups; the values in toluene are H2P-0 (15.5 ns) > H2P-1 (14.9 ns) > H2P-2c (14.4 ns) > H2P-2t (13.8 ns) ∼ H2P-3 (13.8 ns) > H2P4 ≈ (12.8 ns), where "H2P" refers to the core free base porphyrin, the numerical suffix indicates the no. of meso-Ph groups, and "c" and "t" refer to cis and trans, resp. The opposite trend is found for the fluorescence quantum yield; the values in toluene are H2P-0 (0.049) < H2P-1 (0.063) ∼ H2P-2c (0.063) < H2P-2t (0.071) < H2P-3 (0.073) < H2P‾4 (0.090). Similar trends occur in DMF. All radiative and nonradiative (internal conversion and intersystem crossing) rate consts. for S1 decay increase with increasing no. of meso-Ph groups. The increase in the rate const. for fluorescence parallels an increase in oscillator strength of the S0 → S1 absorption manifold. The trend is reproduced by time-dependent d. functional theory calcns. The calcns. within the context of the four-orbital model reveal that the enhanced S0 ↔ S1 radiative probabilities derive from a preferential effect of the meso-Ph groups to raise the energy of the HOMO, which underpins a parallel bathochromic shift in the S0 → S1 absorption wavelength. Polarizations of the S1 and S2 excited states with respect to mol. structural features (e.g., the central proton axis) are analyzed in the context of historical conventions for porphyrins vs. chlorins and bacteriochlorins, where some ambiguity exists, including for porphine, one of the simplest tetrapyrroles. Collectively, the study affords fundamental insights into the photophys. properties and electronic structure of meso-phenylporphyrins that should aid their continued widespread use as benchmarks for tetrapyrrole-based architectures in chem., solar-energy and life-sciences research.
    24. 24
      Suijkerbuijk, B. M. J. M.; Klein Gebbink, R. J. M. Merging Porphyrins with Organometallics: Synthesis and Applications. Angew. Chem. Int. Ed 2008, 47, 7396– 7421,  DOI: 10.1002/anie.200703362
      24
      Merging porphyrins with organometallics: synthesis and applications
      Suijkerbuijk, Bart M. J. M.; Klein Gebbink, Robertus J. M.
      Angewandte Chemie, International Edition (2008), 47 (39), 7396-7421CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A review. The coordination chem. of porphyrins has traditionally involved the ability of the porphyrin's tetrapyrrolic core to accommodate metal ions of varying charges and sizes, and on the organometallic chem. of the resulting metalloporphyrins. However, the organometallic chem. of porphyrins is not necessarily restricted to the metal bound in the porphyrin core, but can also be extended to the porphyrin periphery, be it through direct metalation of the porphyrin macrocycle at the meso or β position, or by attachment to or merger of the porphyrin skeleton with ligands, followed by metalation. This Review focuses on the synthetic strategies used for porphyrins with peripheral metal-carbon bonds. The exciting results that have been produced underscore the importance and future potential of this field.
    25. 25
      Pijeat, J.; Dappe, Y. J.; Thuéry, P.; Campidelli, S. Synthesis and Suzuki–Miyaura Cross Coupling Reactions for Post-Synthetic Modification of a Tetrabromo-Anthracenyl Porphyrin. Org. Biomol. Chem. 2018, 16, 8106– 8114,  DOI: 10.1039/C8OB02150C
      There is no corresponding record for this reference.
    26. 26
      Cooper, C.; Paul, R.; Alsaleh, A.; Washburn, S.; Rackers, W.; Kumar, S.; Nesterov, V. N.; D’Souza, F.; Vinogradov, S. A.; Wang, H. Naphthodithiophene-Fused Porphyrins: Synthesis, Characterization, and Impact of Extended Conjugation on Aromaticity. Chem. - Eur. J. 2023, 29, e202302013  DOI: 10.1002/chem.202302013
      There is no corresponding record for this reference.
    27. 27
      Davis, N. K. S.; Thompson, A. L.; Anderson, H. L. A Porphyrin Fused to Four Anthracenes. J. Am. Chem. Soc. 2011, 133, 30– 31,  DOI: 10.1021/ja109671f
      27
      A Porphyrin Fused to Four Anthracenes
      Davis, Nicola K. S.; Thompson, Amber L.; Anderson, Harry L.
      Journal of the American Chemical Society (2011), 133 (1), 30-31CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      The authors synthesized a fused tetraanthracenylporphyrin by oxidn. of a meso-anthracenyl nickel(II) porphyrin with FeCl3. This compd. exhibits an intense red shifted absorption spectrum (λmax = 1417 nm; ε = 1.2 × 105 M-1 cm-1) and a small electrochem. HOMO-LUMO gap (0.61 eV). The crystal structure shows that it forms π-stacked dimers with a short Ni···Ni distance (3.32 Å).
    28. 28
      Davis, N. K. S.; Thompson, A. L.; Anderson, H. L. Bis-Anthracene Fused Porphyrins: Synthesis, Crystal Structure, and Near-IR Absorption. Org. Lett. 2010, 12, 2124– 2127,  DOI: 10.1021/ol100619p
      28
      Bis-Anthracene Fused Porphyrins: Synthesis, Crystal Structure, and Near-IR Absorption
      Davis, Nicola K. S.; Thompson, Amber L.; Anderson, Harry L.
      Organic Letters (2010), 12 (9), 2124-2127CODEN: ORLEF7; ISSN:1523-7060. (American Chemical Society)
      Synthesis of fused bis-anthracene porphyrin monomers and dimers was achieved by oxidative ring closure using FeCl3 and Sc(OTf)3/DDQ, resp. The fused compds. display red-shifted absorption spectra with maxima in the near-IR at 973 and 1495 nm, resp., and small electrochem. HOMO-LUMO gaps. The crystal structure of the fully fused bis-anthracene porphyrin shows that it has a regular planar π-system.
    29. 29
      Kurotobi, K.; Kim, K. S.; Noh, S. B.; Kim, D.; Osuka, A. A Quadruply Azulene-Fused Porphyrin with Intense Near-IR Absorption and a Large Two-Photon Absorption Cross Section. Angew. Chem., Int. Ed. 2006, 45, 3944– 3947,  DOI: 10.1002/anie.200600892
      29
      A quadruply azulene-fused porphyrin with intense near-IR absorption and a large two-photon absorption cross section
      Kurotobi, Kei; Kim, Kil Suk; Noh, Su Bum; Kim, Dongho; Osuka, Atsuhiro
      Angewandte Chemie, International Edition (2006), 45 (24), 3944-3947CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Azulene-fused nickel porphyrins I-III [Ar = 3,5-(Me3C)2C6H3; R = 2,4,6-(Me3C)3C6H2] were synthesized through the oxidn. of meso-(4-azulenyl)porphyrins with FeCl3. The azulene-fused strategy allowed prepn. of highly ρ-conjugated porphyrinic electronic systems, which show promise as two-photon absorption pigments.
    30. 30
      Davis, N. K. S.; Pawlicki, M.; Anderson, H. L. Expanding the Porphyrin π-System by Fusion with Anthracene. Org. Lett. 2008, 10, 3945– 3947,  DOI: 10.1021/ol801500b
      30
      Expanding the Porphyrin π-System by Fusion with Anthracene
      Davis, Nicola K. S.; Pawlicki, Milosz; Anderson, Harry L.
      Organic Letters (2008), 10 (18), 3945-3947CODEN: ORLEF7; ISSN:1523-7060. (American Chemical Society)
      Synthesis of β,meso,β-anthracene triply fused and β,meso-anthracene doubly fused porphyrins was achieved via oxidative intramol. ring closure of meso-(9-anthryl)porphyrins and meso-(1-anthryl)porphyrins, resp. Fusion was only possible when the anthracene carried electron-donating alkoxy substituents. The fused porphyrins exhibit strongly red shifted UV-visible absorption spectra and reduced electrochem. HOMO-LUMO gaps (relative to the unfused tetraaryl porphyrin precursor).
    31. 31
      Gill, H. S.; Harmjanz, M.; Santamaría, J.; Finger, I.; Scott, M. J. Facile Oxidative Rearrangement of Dispiro-Porphodimethenes to Nonplanar and Sheetlike Porphyrins with Intense Absorptions in the Near-IR Region. Angew. Chem., Int. Ed. 2004, 43, 485– 490,  DOI: 10.1002/anie.200352762
      31
      Facile oxidative rearrangement of dispiro-porphodimethenes to nonplanar and sheetlike porphyrins with intense absorptions in the near-IR region
      Gill, Hubert S.; Harmjanz, Michael; Santamaria, Javier; Finger, Isaac; Scott, Michael J.
      Angewandte Chemie, International Edition (2004), 43 (4), 485-490CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The dispiro-porphodimethene (I, Ar = mesityl; R = H, tert-butyl) was prepd. and metalated with Cu or Pd. These Cu and Pd dispiro-porphodimethene complexes were then oxidized with rearrangement to yield complexes of the corresponding cycloheptanones (II, III). Complexes of II or III were then further oxidized to yield Cu and Pd complexes of IV and V. Exceedingly large, planar porphyrin systems composed of 49 nonhydrogen nuclei in highly delocalized at. systems display exceptionally low-energy transitions in UV/visible/NIR spectroscopy and in cyclic voltammetry. The spectra shown are for cis Pd complex depicted and the corresponding trans isomer.
    32. 32
      Diev, V. V.; Hanson, K.; Zimmerman, J. D.; Forrest, S. R.; Thompson, M. E. Fused Pyrene–Diporphyrins: Shifting Near-Infrared Absorption to 1.5 Mm and Beyond. Angew. Chem., Int. Ed. 2010, 49, 5523– 5526,  DOI: 10.1002/anie.201002669
      32
      Fused Pyrene-Diporphyrins: Shifting Near-Infrared Absorption to 1.5 μm and Beyond
      Diev, Vyacheslav V.; Hanson, Kenneth; Zimmerman, Jeramy D.; Forrest, Stephen R.; Thompson, Mark E.
      Angewandte Chemie, International Edition (2010), 49 (32), 5523-5526, S5523/1-S5523/21CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The prepn. of a new class of diporphyrin-pyrene hybrid compds. via a relatively simple method is reported. The key step is the oxidative ring closure of the pyrene with the porphyrin core. Pyrene-substituted zinc porphyrin fused dimer I (Ar = 3,5-di-tert-butylphenyl) was prepd. in two steps (Suzuki coupling and Osuka's oxidative fusion of porphyrin rings) starting from a disubstituted zinc metalloporphyrin. Double fusion of two pyrene rings with the diporphyrin moiety to give II (M = H2, same Ar) is accomplished with anhyd. FeCl3 in CH2Cl2. This crude product can be readily metalated to afford II (M = Zn, Pb). The direct fusion of arom. rings to porphyrins occurred without the need to activate porphyrin rings with nickel, or the arom. rings with alkoxy groups. The UV-visible-NIR spectra of I and II (M = H2, Zn, Pb) were studied, and their redox potentials were detd. by cyclic voltammetry. Thin films of II (M = H2, Zn, Pb) contg. different ratios of [6,6]-phenyl-C61-butyric acid Me ester (PCBM) were prepd. and noncovalent interactions between the porphyrins and π-conjugated acceptors were studied by UV-visible-NIR spectroscopy. Pyrene-fused dimers II were used as active materials in NIR photodetectors, and give external quantum efficiencies of ≤ 6.5% at λ = 1350 nm for II (M = Zn). The effect of arom. ring fusion to porphyrin tapes in a (meso,β) mode was also explored by DFT methods for several diporphyrin core systems.
    33. 33
      Jiao, C.; Huang, K.-W.; Guan, Z.; Xu, Q.-H.; Wu, J. N-Annulated Perylene Fused Porphyrins with Enhanced Near-IR Absorption and Emission. Org. Lett. 2010, 12, 4046– 4049,  DOI: 10.1021/ol1016383
      33
      N-Annulated Perylene Fused Porphyrins with Enhanced Near-IR Absorption and Emission
      Jiao, Chongjun; Huang, Kuo-Wei; Guan, Zhenping; Xu, Qing-Hua; Wu, Jishan
      Organic Letters (2010), 12 (18), 4046-4049CODEN: ORLEF7; ISSN:1523-7060. (American Chemical Society)
      N-Annulated perylene fused porphyrins 1 and 2 were synthesized by oxidative dehydrogenation using a Sc(OTf)3/DDQ system. These newly synthesized hybrid mols. are highly sol. in org. solvents and exhibit remarkably intense near-IR absorption, as well as detectable photoluminescence quantum yields, all of which are comparable to or even exceed those of either meso-β doubly linked porphyrin dimer/trimer or bis/tri-N-annulated perylenes.
    34. 34
      Richeter, S.; Jeandon, C.; Kyritsakas, N.; Ruppert, R.; Callot, H. J. Preparation of Six Isomeric Bis-Acylporphyrins with Chromophores Reaching the Near-Infrared via Intramolecular Friedel–Crafts Reaction. J. Org. Chem. 2003, 68, 9200– 9208,  DOI: 10.1021/jo035108m
      34
      Preparation of Six Isomeric Bis-acylporphyrins with Chromophores Reaching the Near-Infrared via Intramolecular Friedel-Crafts Reaction
      Richeter, Sebastien; Jeandon, Christophe; Kyritsakas, Nathalie; Ruppert, Romain; Callot, Henry J.
      Journal of Organic Chemistry (2003), 68 (24), 9200-9208CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)
      The prepn. of six diketones based on the frameworks of five bis-naphthoporphyrins and one perinaphthoporphyrin is described. All diketones derive from meso-tetraarylporphyrins having incorporated two carbonyl groups, each one connected to one β-pyrrole carbon and one ortho carbon atom from a meso-aryl group. These compds. were all produced in good yield by intramol. Friedel-Crafts acylation, either from porphyrins meso-substituted by o-carboxyphenyl or o,o'-dicarboxyphenyl substituents or from porphyrins bearing carboxy groups attached to the pyrrolic β-positions. Although the former reaction does not show significant regioselectivity when run on nickel complexes, the opposite is true for the corresponding free bases. All diketones show a spectacular bathochromic shift of the UV-vis absorption, the longest wavelength bands absorbing in the 700-825 nm range. Two compds. were structurally characterized by X-ray diffraction. In the case of the diketone, whose carbonyl groups are attached to vicinal pyrrolic β-positions, a significant intermol. interaction between the two carbonyl groups and an arom. hydrogen atom was detected.
    35. 35
      Saegusa, Y.; Ishizuka, T.; Komamura, K.; Shimizu, S.; Kotani, H.; Kobayashi, N.; Kojima, T. Ring-Fused Porphyrins: Extension of π-Conjugation Significantly Affects the Aromaticity and Optical Properties of the Porphyrin π-Systems and the Lewis Acidity of the Central Metal Ions. Phys. Chem. Chem. Phys. 2015, 17, 15001– 15011,  DOI: 10.1039/C5CP01420D
      35
      Ring-fused porphyrins: extension of π-conjugation significantly affects the aromaticity and optical properties of the porphyrin π-systems and the Lewis acidity of the central metal ions
      Saegusa, Yuta; Ishizuka, Tomoya; Komamura, Keiyu; Shimizu, Soji; Kotani, Hiroaki; Kobayashi, Nagao; Kojima, Takahiko
      Physical Chemistry Chemical Physics (2015), 17 (22), 15001-15011CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      Here, the authors report the effects of ring fusion, which causes expansion of the π-conjugation circuits of the porphyrin derivs. to the fused meso-aryl groups, on the aromaticity and the magnetic properties of porphyrin derivs. These studies revealed the facts that the ring fusion with five-membered rings causes not only the remarkable red shifts of the absorption bands and narrowed HOMO-LUMO gaps, but also the contribution of anti-arom. resonance forms to the magnetic properties as obsd. in the 1H NMR spectra. The optical absorption and MCD spectroscopies indicate that the increase in the no. of the fused rings causes stabilization of the LUMO level of the porphyrin derivs. and as a result induces the loosening of the LUMO degeneracy that is generally obsd. for porphyrins. The electronic structure of a quadruply fused porphyrin deriv. was exptl. clarified by the ESR studies on the 1e--oxidized and 1e--reduced species in THF. Also, the authors revealed the substituent effects of the fused meso-aryl groups of quadruply fused porphyrins (QFPs) on the crystal structures, absorption spectra and redox potentials; the sensitiveness of the substituent effects shows that the π-conjugation circuits extended to the fused meso-aryl groups. Addnl., the elongation of the bond lengths between the pyrrolic nitrogen and the central metal ions in QFP-metal complexes causes a remarkable increase of the Lewis acidity of the central metal ions.
    36. 36
      Tokuji, S.; Takahashi, Y.; Shinmori, H.; Shinokubo, H.; Osuka, A. Synthesis of a Pyridine-Fused Porphyrinoid: Oxopyridochlorin. Chem. Commun. 2009, 1028– 1030,  DOI: 10.1039/b819284g
      36
      Synthesis of a pyridine-fused porphyrinoid: oxopyridochlorin
      Tokuji, Sumito; Takahashi, Yuji; Shinmori, Hideyuki; Shinokubo, Hiroshi; Osuka, Atsuhiro
      Chemical Communications (Cambridge, United Kingdom) (2009), (9), 1028-1030CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      Treatment of 3,5-dibenzoylporphyrins with ammonium acetate provides oxopyridochlorins I [M = H2, Ni, Zn; R = 3,5-(Me3C)2C6H3] as the first examples of pyridine-fused porphyrinoids. I display absorption bands at wavelengths from 400-1000 nm (into the near IR region), with the absorption band for I (M = Ni) increasing significantly in width upon protonation. I (M = H2, Zn) sensitize the formation of singlet oxygen with quantum yields of 0.52-0.79 and do not decomp. under the irradn. conditions. The structures of I·2 MeOH (M = Zn), I·MeOH (M = H2), and I·3 (ClCH2CH2Cl) (M = Ni) are detd. by X-ray crystallog.
    37. 37
      Lewtak, J. P.; Gryko, D. T. Synthesis of π-Extended Porphyrins via Intramolecular Oxidative Coupling. Chem. Commun. 2012, 48, 10069– 10086,  DOI: 10.1039/c2cc31279d
      37
      Synthesis of π-extended porphyrins via intramolecular oxidative coupling
      Lewtak, Jan P.; Gryko, Daniel T.
      Chemical Communications (Cambridge, United Kingdom) (2012), 48 (81), 10069-10086CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      A review. Porphyrins fused with other arom. units at the meso- and β-positions have recently emerged as a hot topic of research. Their synthesis typically starts with prepn. of precursors via either Suzuki coupling of a meso-bromoporphyrin or mixed-aldehyde condensation, and is followed by oxidative arom. coupling, often using high-valent metal reagents (DDQ/Sc(OTf)3 and Fe(iii) salts are among the most popular). In recent years, porphyrins were oxidatively coupled not only with well-known arom. hydrocarbons such as naphthalene and pyrene, but also with more complex heterocyclic fragments, including indole, phenanthro[1,10,9,8-cdefg]carbazole and BODIPY. A subtle relationship exists between the output of intramol. oxidative coupling and the nature of the second arom. moiety, cation in the porphyrin cavity, oxidant, and type of remaining meso-substituent. The extension of the porphyrin chromophore leads to significant change in linear and non-linear optical properties. Very strong bathochromic shifts of absorption (λmax reaching 1.5-2 μ in some cases) and increases in two-photon absorption cross-sections are typical for these functional dyes.
    38. 38
      Moss, A.; Jang, Y.; Arvidson, J.; N Nesterov, V.; D’Souza, F.; Wang, H. Aromatic Heterobicycle-Fused Porphyrins: Impact on Aromaticity and Excited State Electron Transfer Leading to Long-Lived Charge Separation. Chem. Sci. 2022, 13, 9880– 9890,  DOI: 10.1039/D2SC03238D
      38
      Aromatic heterobicycle-fused porphyrins: impact on aromaticity and excited state electron transfer leading to long-lived charge separation
      Moss, Austen; Jang, Youngwoo; Arvidson, Jacob; Nesterov, Vladimir N.; D'Souza, Francis; Wang, Hong
      Chemical Science (2022), 13 (34), 9880-9890CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
      A new synthetic method to fuse benzo[4,5]imidazo[2,1-a]isoindole to the porphyrin periphery at the β,β-positions has been developed, and its impact on the aromaticity and electronic structures is investigated. Reactivity investigation of the fused benzoimidazo-isoindole component reveals fluorescence quenching of a zinc porphyrin (AMIm-2) upon treatment with a Bronsted acid. The reaction of the zinc porphyrin (AMIm-2) with Me iodide initiated a new org. transformation, resulting in the ring-opening of isoindole with the formation of an aldehyde and dimethylation of the benzoimidazo component. The fused benzoimidazo-isoindole component acted as a good ligand to bind platinum(II), forming novel homobimetallic and heterobimetallic porphyrin complexes. The fusion of benzoimidazo-isoindole on the porphyrin ring resulted in bathochromically shifted absorptions and emissions, reflecting the extended conjugation of the porphyrin π-system. Time-resolved emission and transient absorption spectroscopy revealed stable excited state species of the benzoimidazo-isoindole fused porphyrins. Zinc porphyrin AMIm-2 promoted excited state electron transfer upon coordinating with an electron acceptor, C60, generating a long-lived charge-sepd. state, in the order of 37.4 μs. The formation of the exceptionally long-lived charge-sepd. state is attributed to the involvement of both singlet and triplet excited states of AMIm-2, which is rarely reported in porphyrins.
    39. 39
      Liu, Z.; Fu, S.; Liu, X.; Narita, A.; Samorì, P.; Bonn, M.; Wang, H. I. Small Size, Big Impact: Recent Progress in Bottom-Up Synthesized Nanographenes for Optoelectronic and Energy Applications. Adv. Sci. 2022, 9, 2106055  DOI: 10.1002/advs.202106055
      There is no corresponding record for this reference.
    40. 40
      Björk, J.; Hanke, F. Towards Design Rules for Covalent Nanostructures on Metal Surfaces. Chem. - Eur. J. 2014, 20, 928– 934,  DOI: 10.1002/chem.201303559
      There is no corresponding record for this reference.
    41. 41
      Clair, S.; de Oteyza, D. G. Controlling a Chemical Coupling Reaction on a Surface: Tools and Strategies for On-Surface Synthesis. Chem. Rev. 2019, 119, 4717– 4776,  DOI: 10.1021/acs.chemrev.8b00601
      41
      Controlling a Chemical Coupling Reaction on a Surface: Tools and Strategies for On-Surface Synthesis
      Clair, Sylvain; de Oteyza, Dimas G.
      Chemical Reviews (Washington, DC, United States) (2019), 119 (7), 4717-4776CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. On-surface synthesis is appearing as an extremely promising research field aimed at creating new org. materials. A large no. of chem. reactions have been successfully demonstrated to take place directly on surfaces through unusual reaction mechanisms. In some cases the reaction conditions can be properly tuned to steer the formation of the reaction products. It is thus possible to control the initiation step of the reaction and its degree of advancement (the kinetics, the reaction yield); the nature of the reaction products (selectivity control, particularly in the case of competing processes); as well as the structure, position, and orientation of the covalent compds., or the quality of the as-formed networks in terms of order and extension. The aim of our review is thus to provide an extensive description of all tools and strategies reported to date and to put them into perspective. We specifically define the different approaches available and group them into a few general categories. In the last part, we demonstrate the effective maturation of the on-surface synthesis field by reporting systems that are getting closer to application-relevant levels thanks to the use of advanced control strategies.
    42. 42
      Song, S.; Su, J.; Telychko, M.; Li, J.; Li, G.; Li, Y.; Su, C.; Wu, J.; Lu, J. On-Surface Synthesis of Graphene Nanostructures with π-Magnetism. Chem. Soc. Rev. 2021, 50, 3238– 3262,  DOI: 10.1039/D0CS01060J
      42
      On-surface synthesis of graphene nanostructures with π-magnetism
      Song, Shaotang; Su, Jie; Telychko, Mykola; Li, Jing; Li, Guangwu; Li, Ying; Su, Chenliang; Wu, Jishan; Lu, Jiong
      Chemical Society Reviews (2021), 50 (5), 3238-3262CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      A review. Graphene nanostructures (GNs) including graphene nanoribbons and nanoflakes have attracted tremendous interest in the field of chem. and materials science due to their fascinating electronic, optical and magnetic properties. Among them, zigzag-edged GNs (ZGNs) with precisely-tunable π-magnetism hold great potential for applications in spintronics and quantum devices. To improve the stability and processability of ZGNs, substitutional groups are often introduced to protect the reactive edges in org. synthesis, which renders the study of their intrinsic properties difficult. In contrast to the conventional wet-chem. method, on-surface bottom-up synthesis presents a promising approach for the fabrication of both unsubstituted ZGNs and functionalized ZGNs with at. precision via surface-catalyzed transformation of rationally-designed precursors. The structural and spin-polarized electronic properties of these ZGNs can then be characterized with sub-mol. resoln. by means of scanning probe microscopy techniques. This aims to highlight recent advances in the on-surface synthesis and characterization of a diversity of ZGNs with π-magnetism. We also discuss the important role of precursor design and reaction stimuli in the on-surface synthesis of ZGNs and their π-magnetism origin. Finally, we will highlight the existing challenges and future perspective surrounding the synthesis of novel open-shell ZGNs towards next-generation quantum technol.
    43. 43
      Gaweł, P.; Foroutan-Nejad, C. Carbon Rings Push Limits of Chemical Theories. Nature 2023, 623, 922– 924,  DOI: 10.1038/d41586-023-03575-5
      There is no corresponding record for this reference.
    44. 44
      Cai, Z.-F.; Chen, T.; Wang, D. Insights into the Polymerization Reactions on Solid Surfaces Provided by Scanning Tunneling Microscopy. J. Phys. Chem. Lett. 2023, 14, 2463– 2472,  DOI: 10.1021/acs.jpclett.2c03943
      There is no corresponding record for this reference.
    45. 45
      Shen, Q.; Gao, H.-Y.; Fuchs, H. Frontiers of On-Surface Synthesis: From Principles to Applications. Nano Today 2017, 13, 77– 96,  DOI: 10.1016/j.nantod.2017.02.007
      45
      Frontiers of on-surface synthesis: From principles to applications
      Shen, Qian; Gao, Hong-Ying; Fuchs, Harald
      Nano Today (2017), 13 (), 77-96CODEN: NTAOCG; ISSN:1748-0132. (Elsevier Ltd.)
      On-surface synthesis is the bottom-up construction of covalent bonds between mol. building blocks, which has been greatly developed during the past decade. Dozens of reactions have been successfully realized and scrutinized on various surfaces with the help of surface science techniques combined with theor. calcns. Functional nanoarchitectures such as one-dimensional nanowires, nanoribbons and two-dimensional nanonetworks have been constructed on surfaces and explored in several potential applications. In fact, the generation of multilevel nanostructures will play a key role in future soft nanoscience and technologies due to their emergent properties ranging far beyond those of the individual mols. building them up. In this review, we discuss selected examples of important processes in on-surface synthesis developed in recent years and summarize them under the following aspects: (1) on-surface reactions in a category of different carbon types; (2) techniques applied in on-surface synthesis; (3) on-surface synthesized functional nanostructures; and (4) potential applications of on-surface synthesized nano-materials. The review concludes with a perspective of the future development of on-surface synthesis.
    46. 46
      Xing, G.-Y.; Zhu, Y.-C.; Li, D.-Y.; Liu, P.-N. On-Surface Cross-Coupling Reactions. J. Phys. Chem. Lett. 2023, 14, 4462– 4470,  DOI: 10.1021/acs.jpclett.3c00344
      There is no corresponding record for this reference.
    47. 47
      Qin, T.; Wang, T.; Zhu, J. Recent Progress in On-Surface Synthesis of Nanoporous Graphene Materials. Commun. Chem. 2024, 7, 154  DOI: 10.1038/s42004-024-01222-2
      There is no corresponding record for this reference.
    48. 48
      Sooambar, C.; Troiani, V.; Bruno, C.; Marcaccio, M.; Paolucci, F.; Listorti, A.; Belbakra, A.; Armaroli, N.; Magistrato, A.; Zorzi, R. D.; Geremia, S.; Bonifazi, D. Synthesis, Photophysical, Electrochemical, and Electrochemiluminescent Properties of 5,15-Bis(9-Anthracenyl)Porphyrin Derivatives. Org. Biomol. Chem. 2009, 7, 2402– 2413,  DOI: 10.1039/b820210a
      48
      Synthesis, photophysical, electrochemical, and electrochemiluminescent properties of 5,15-bis(9-anthracenyl)porphyrin derivatives
      Sooambar, Chloe; Troiani, Vincent; Bruno, Carlo; Marcaccio, Massimo; Paolucci, Francesco; Listorti, Andrea; Belbakra, Abdelhalim; Armaroli, Nicola; Magistrato, Alessandra; De Zorzi, Rita; Geremia, Silvano; Bonifazi, Davide
      Organic & Biomolecular Chemistry (2009), 7 (11), 2402-2413CODEN: OBCRAK; ISSN:1477-0520. (Royal Society of Chemistry)
      Novel 5,15-bis(9-anthracenyl)porphyrin derivs. (I; R = H, C6H4NMe2-4) were synthesized by stepwise Suzuki-type coupling reactions using anthracenyl-boronates bearing various electronically active moieties. Absorption spectra of these porphyrin conjugates reveal some degree of delocalization with the directly linked chromophores, particularly in the case of anthracenyl-porphyrin bearing dimethylanilino moieties at the two extremities. Fluorescence and 77 K phosphorescence properties indicate that the excitation energy is invariably funnelled to the lowest singlet and triplet states of the porphyrin chromophore. The latter levels have been probed also by transient absorption spectroscopy, showing the typical triplet features detected in meso-substituted porphyrins. Extensive electrochem. studies have been performed to unravel the electronic properties of the newly synthesized porphyrins. Low-temp. cyclic voltammetry investigations showed that the anthracenyl-porphyrins are capable of undergoing as many as four electron transfer processes. In particular, by means of UV-Vis-NIR spectroelectrochem. measurements, a NIR-centered intramol. photoinduced intervalence charge transfer (IV-CT) from a neutral N,N-dimethylanilino moiety to the N,N-dimethylanilino radical cation has been obsd. for the doubly-oxidized porphyrin II. The mols. also showed unexpected electrogenerated chemiluminescence properties, which revealed to be largely controlled by the electronic characteristics of the peripheral anthracenyl substituents. The structural and the electronic properties of these complexes have been also characterized by DFT calcns., as well as by X-ray crystallog. analyses.
    49. 49
      Volz, H.; Schäffer, H. Mesosubstituted Porphyrins. III. 5,10,15,20-Tetraanthracenylporphyrin. Chem.-Ztg. 1985, 109, 308– 309
      49
      Mesosubstituted porphyrins. III. 5,10,15,20-Tetraanthracenylporphyrin
      Volz, Heinrich; Schaeffer, Hermann
      Chemiker-Zeitung (1985), 109 (9), 308-9CODEN: CMKZAT; ISSN:0009-2894.
      The title porphyrin was prepd. in 5.65% overall yield by treating 2-formylpyrrole with 9-lithioanthracene and tetramerizing the resulting carbinol in EtCO2H-PhMe, followed by DDQ oxidn. of residual chlorin in the product.
    50. 50
      Wäckerlin, C. On-Surface Hydrogen/Deuterium Isotope Exchange in Polycyclic Aromatic Hydrocarbons. Angew. Chem. Int. Ed. 2021, 60, 8446– 8449,  DOI: 10.1002/ange.202015552
      There is no corresponding record for this reference.
    51. 51
      Cai, J.; Ruffieux, P.; Jaafar, R.; Bieri, M.; Braun, T.; Blankenburg, S.; Muoth, M.; Seitsonen, A. P.; Saleh, M.; Feng, X.; Müllen, K.; Fasel, R. Atomically Precise Bottom-up Fabrication of Graphene Nanoribbons. Nature 2010, 466, 470– 473,  DOI: 10.1038/nature09211
      51
      Atomically precise bottom-up fabrication of graphene nanoribbons
      Cai, Jinming; Ruffieux, Pascal; Jaafar, Rached; Bieri, Marco; Braun, Thomas; Blankenburg, Stephan; Muoth, Matthias; Seitsonen, Ari P.; Saleh, Moussa; Feng, Xinliang; Muellen, Klaus; Fasel, Roman
      Nature (London, United Kingdom) (2010), 466 (7305), 470-473CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)
      Graphene nanoribbons-narrow and straight-edged stripes of graphene, or single-layer graphite-are predicted to exhibit electronic properties that make them attractive for the fabrication of nanoscale electronic devices. In particular, although the two-dimensional parent material graphene exhibits semimetallic behavior, quantum confinement and edge effects should render all graphene nanoribbons with widths smaller than 10 nm semiconducting. But exploring the potential of graphene nanoribbons is hampered by their limited availability: although they were made using chem., sonochem. and lithog. methods as well as through the unzipping of carbon nanotubes, the reliable prodn. of graphene nanoribbons smaller than 10 nm with chem. precision remains a significant challenge. Here the authors report a simple method for the prodn. of atomically precise graphene nanoribbons of different topologies and widths, which uses surface-assisted coupling of mol. precursors into linear polyphenylenes and their subsequent cyclodehydrogenation. The topol., width and edge periphery of the graphene nanoribbon products are defined by the structure of the precursor monomers, which can be designed to give access to a wide range of different graphene nanoribbons. The authors expect that the authors' bottom-up approach to the atomically precise fabrication of graphene nanoribbons will finally enable detailed exptl. studies of the properties of this exciting class of materials. It should even provide a route to graphene nanoribbon structures with engineered chem. and electronic properties, including the theor. predicted intraribbon quantum dots, superlattice structures and magnetic devices based on specific graphene nanoribbon edge states.
    52. 52
      Mateo, L. M.; Sun, Q.; Liu, S.-X.; Bergkamp, J. J.; Eimre, K.; Pignedoli, C. A.; Ruffieux, P.; Decurtins, S.; Bottari, G.; Fasel, R.; Torres, T. On-Surface Synthesis and Characterization of Triply Fused Porphyrin–Graphene Nanoribbon Hybrids. Angew. Chem., Int. Ed. 2020, 59, 1334– 1339,  DOI: 10.1002/anie.201913024
      52
      On-Surface Synthesis and Characterization of Triply Fused Porphyrin-Graphene Nanoribbon Hybrids
      Mateo, Luis M.; Sun, Qiang; Liu, Shi-Xia; Bergkamp, Jesse J.; Eimre, Kristjan; Pignedoli, Carlo A.; Ruffieux, Pascal; Decurtins, Silvio; Bottari, Giovanni; Fasel, Roman; Torres, Tomas
      Angewandte Chemie, International Edition (2020), 59 (3), 1334-1339CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      On-surface synthesis offers a versatile approach to prep. novel carbon-based nanostructures that cannot be obtained by conventional soln. chem. Graphene nanoribbons (GNRs) have potential for a variety of applications. A key issue for their application in mol. electronics is in the fine-tuning of their electronic properties through structural modifications, such as heteroatom doping or the incorporation of non-benzenoid rings. In this context, the covalent fusion of GNRs and porphyrins (Pors) is a highly appealing strategy. Herein we present the selective on-surface synthesis of a Por-GNR hybrid, which consists of two Pors connected by a short GNR segment. The atomically precise structure of the Por-GNR hybrid has been characterized by bond-resolved scanning tunneling microscopy (STM) and noncontact at. force microscopy (nc-AFM). The electronic properties have been investigated by scanning tunneling spectroscopy (STS), in combination with DFT calcns., which reveals a low electronic gap of 0.4 eV.
    53. 53
      Kawai, S.; Ishikawa, A.; Ishida, S.; Yamakado, T.; Ma, Y.; Sun, K.; Tateyama, Y.; Pawlak, R.; Meyer, E.; Saito, S.; Osuka, A. On-Surface Synthesis of Porphyrin-Complex Multi-Block Co-Oligomers by Defluorinative Coupling. Angew. Chem., Int. Ed. 2022, 61, e202114697  DOI: 10.1002/anie.202114697
      53
      On-Surface Synthesis of Porphyrin-Complex Multi-Block Co-Oligomers by Defluorinative Coupling
      Kawai, Shigeki; Ishikawa, Atsushi; Ishida, Shin-ichiro; Yamakado, Takuya; Ma, Yujing; Sun, Kewei; Tateyama, Yoshitaka; Pawlak, Remy; Meyer, Ernst; Saito, Shohei; Osuka, Atsuhiro
      Angewandte Chemie, International Edition (2022), 61 (3), e202114697CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      On-surface chem. reaction has become a very powerful technique to synthesize nanostructures by linking small mols. in the bottom-up approach. Given the fact that most reactants are simultaneously activated at certain temps., a sequential reaction in a controlled way has remained challenging. Here, the authors present an on-surface synthesis of multi-block cooligomers from trifluoromethyl (CF3) substituted porphyrin metal complexes. The oligomerization on Au(111) is demonstrated with a combination of bond-resolved scanning probe microscopy and d. functional theory (DFT) calcns. Even after the first oligomerization of single monomer unit, the termini of the oligomer keep the CF3 group, which can be used as a reactant for further coupling in a sequential order. Consequently, copper, cobalt, and palladium complexes of bisanthracene-fused porphyrin oligomers were linked with each other in a designed order.
    54. 54
      Sen, D.; Błoński, P.; de la Torre, B.; Jelínek, P.; Otyepka, M. Thermally Induced Intra-Molecular Transformation and Metalation of Free-Base Porphyrin on Au(111) Surface Steered by Surface Confinement and Ad-Atoms. Nanoscale Adv. 2020, 2, 2986– 2991,  DOI: 10.1039/D0NA00401D
      54
      Thermally induced intra-molecular transformation and metalation of free-base porphyrin on Au(111) surface steered by surface confinement and ad-atoms
      Sen, Dipayan; Blonski, Piotr; Torre, Bruno de la; Jelinek, Pavel; Otyepka, Michal
      Nanoscale Advances (2020), 2 (7), 2986-2991CODEN: NAADAI; ISSN:2516-0230. (Royal Society of Chemistry)
      We investigated chem. transformations of a fluorinated free-base porphyrin, 5,10,15,20-tetrakis(4-fluorophenyl)-21,23H-porphyrin (2H-4FTPP) under a Au(111) surface confinement and including gold adatoms by using an expt. and d. functional theory based first-principles calcns. Annealing of 2H-4FTPP led to cyclodehydrogenation of the mol. to a π-extended fused arom. planar compd., 2H-4FPP, and metalation of the porphyrin ring by Au atoms to Au-4FPP complex. Noticeable lowering of bond-dissocn. energies of the pyrrole's C-H bonds of the Au(111) supported mol. with respect to their values in the gas phase explained the obsd. on-surface planarization. Our findings also indicate that Au adatoms may catalyze cleavage of C-H/F bonds in temp.-initiated processes on Au surfaces. BDEs and explicit inclusion of Au adatoms helps to rationalize thermally induced chem. reactions on the resp. surface.
    55. 55
      Lowe, B.; Hellerstedt, J.; Matěj, A.; Mutombo, P.; Kumar, D.; Ondráček, M.; Jelinek, P.; Schiffrin, A. Selective Activation of Aromatic C–H Bonds Catalyzed by Single Gold Atoms at Room Temperature. J. Am. Chem. Soc. 2022, 144, 21389– 21397,  DOI: 10.1021/jacs.2c10154
      55
      Selective activation of aromatic C-H bonds catalyzed by single gold atoms at room temperature
      Lowe, Benjamin; Hellerstedt, Jack; Matej, Adam; Mutombo, Pingo; Kumar, Dhaneesh; Ondracek, Martin; Jelinek, Pavel; Schiffrin, Agustin
      Journal of the American Chemical Society (2022), 144 (46), 21389-21397CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Selective activation and controlled functionalization of C-H bonds in org. mols. is one of the most desirable processes in synthetic chem. Despite progress in heterogeneous catalysis using metal surfaces, this goal remains challenging due to the stability of C-H bonds and their ubiquity in precursor mols., hampering regioselectivity. Here, we examine the interaction between 9,10-dicyanoanthracene (DCA) mols. and Au adatoms on a Ag(111) surface at room temp. (RT). Characterization via low-temp. scanning tunneling microscopy, spectroscopy, and noncontact at. force microscopy, supported by theor. calcns., revealed the formation of organometallic DCA-Au-DCA dimers, where C atoms at the ends of the anthracene moieties are bonded covalently to single Au atoms. The formation of this organometallic compd. is initiated by a regioselective cleaving of C-H bonds at RT. Hybrid quantum mechanics/mol. mechanics calcns. show that this regioselective C-H bond cleaving is enabled by an intermediate metal-org. complex which significantly reduces the dissocn. barrier of a specific C-H bond. Harnessing the catalytic activity of single metal atoms, this regioselective on-surface C-H activation reaction at RT offers promising routes for future synthesis of functional org. and organometallic materials.
    56. 56
      Mendieta-Moreno, J. I.; Mallada, B.; de la Torre, B.; Cadart, T.; Kotora, M.; Jelínek, P. Unusual Scaffold Rearrangement in Polyaromatic Hydrocarbons Driven by Concerted Action of Single Gold Atoms on a Gold Surface. Angew. Chem., Int. Ed. 2022, 61, e202208010  DOI: 10.1002/anie.202208010
      56
      Unusual Scaffold Rearrangement in Polyaromatic Hydrocarbons Driven by Concerted Action of Single Gold Atoms on a Gold Surface
      Mendieta-Moreno, Jesus I.; Mallada, Benjamin; de la Torre, Bruno; Cadart, Timothee; Kotora, Martin; Jelinek, Pavel
      Angewandte Chemie, International Edition (2022), 61 (50), e202208010CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Chem. transformation of polyarom. hydrocarbon (PAH) mols. following different reaction strategies has always been the focus of org. synthesis. In this work, we report the synthesis of a PAH mol., formation of which consists of an unusual C-C bond cleavage accompanied by a complex π-conjugated mol. scaffold rearrangement. We demonstrate that the complex chem. transformation is steered by concerted motion of individual Au0 gold atoms on a supporting Au(111) surface. This observation underpins the importance of single-atom catalysis mediated by adatoms in on-surface synthesis as well as catalytic activity of single Au0 atoms facilitating cleavage of covalent carbon bonds.
    57. 57
      Björk, J.; Sánchez-Sánchez, C.; Chen, Q.; Pignedoli, C. A.; Rosen, J.; Ruffieux, P.; Feng, X.; Narita, A.; Müllen, K.; Fasel, R. The Role of Metal Adatoms in a Surface-Assisted Cyclodehydrogenation Reaction on a Gold Surface. Angew. Chem., Int. Ed. 2022, 61, e202212354  DOI: 10.1002/anie.202212354
      57
      The Role of Metal Adatoms in a Surface-Assisted Cyclodehydrogenation Reaction on a Gold Surface
      Bjork, Jonas; Sanchez-Sanchez, Carlos; Chen, Qiang; Pignedoli, Carlo A.; Rosen, Johanna; Ruffieux, Pascal; Feng, Xinliang; Narita, Akimitsu; Muellen, Klaus; Fasel, Roman
      Angewandte Chemie, International Edition (2022), 61 (49), e202212354CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Dehydrogenation reactions are key steps in many metal-catalyzed chem. processes and in the on-surface synthesis of atomically precise nanomaterials. The principal role of the metal substrate in these reactions is undisputed, but the role of metal adatoms remains, to a large extent, unanswered, particularly on gold substrates. Here, we discuss their importance by studying the surface-assisted cyclodehydrogenation on Au(111) as an ideal model case. We choose a polymer theor. predicted to give one of two cyclization products depending on the presence or absence of gold adatoms. Scanning probe microscopy expts. observe only the product assocd. with adatoms. We challenge the prevalent understanding of surface-assisted cyclodehydrogenation, unveiling the catalytic role of adatoms and their effect on regioselectivity. The study adds new perspectives to the understanding of metal catalysis and the design of on-surface synthesis protocols for novel carbon nanomaterials.
    58. 58
      Frezza, F.; Matěj, A.; Sánchez-Grande, A.; Carrera, M.; Mutombo, P.; Kumar, M.; Curiel, D.; Jelínek, P. On-Surface Synthesis of a Radical 2D Supramolecular Organic Framework. J. Am. Chem. Soc. 2024, 146, 3531– 3538,  DOI: 10.1021/jacs.3c13702
      There is no corresponding record for this reference.
    59. 59
      Frampton, E. S.; Edmondson, M.; Judd, C. J.; Duncan, D. A.; Jones, R. G.; Saywell, A. Self-Metalation of Tetraphenyl Porphyrin on Au(111): Structural Characterisation via X-Ray Standing Wave Analysis. Inorg. Chim. Acta 2023, 558, 121718  DOI: 10.1016/j.ica.2023.121718
      There is no corresponding record for this reference.
    60. 60
      Edmondson, M.; Frampton, E. S.; Judd, C. J.; Champness, N. R.; Jones, R. G.; Saywell, A. Order, Disorder, and Metalation of Tetraphenylporphyrin (2H-TPP) on Au(111). Chem. Commun. 2022, 58, 6247– 6250,  DOI: 10.1039/D2CC00820C
      60
      Order, disorder, and metalation of tetraphenylporphyrin (2H-TPP) on Au(111)
      Edmondson, Matthew; Frampton, Eleanor S.; Judd, Chris J.; Champness, Neil R.; Jones, Robert G.; Saywell, Alex
      Chemical Communications (Cambridge, United Kingdom) (2022), 58 (42), 6247-6250CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      A thermally induced order-disorder transition of tetraphenylporphyrin (2H-TPP) on Au(111) is characterised by scanning probe microscopy and XPS-based techniques. We obsd. that a transition from an ordered close-packed phase to a disordered diffuse phase is correlated with an on-surface cyclodehydrogenation reaction, and that addnl. heating of this diffuse phase gives rise to a single distinct nitrogen environment indicative of the formation of a Au-TPP species.
    61. 61
      Kalashnyk, N.; Daher Mansour, M.; Pijeat, J.; Plamont, R.; Bouju, X.; Balaban, T. S.; Campidelli, S.; Masson, L.; Clair, S. Edge-On Self-Assembly of Tetra-Bromoanthracenyl-Porphyrin on Silver Surfaces. J. Phys. Chem. C 2020, 124, 22137– 22142,  DOI: 10.1021/acs.jpcc.0c05908
      61
      Edge-On Self-Assembly of Tetra-bromoanthracenyl-porphyrin on Silver Surfaces
      Kalashnyk, Nataliya; Daher Mansour, Michel; Pijeat, Joffrey; Plamont, Remi; Bouju, Xavier; Balaban, Teodor Silviu; Campidelli, Stephane; Masson, Laurence; Clair, Sylvain
      Journal of Physical Chemistry C (2020), 124 (40), 22137-22142CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      Mol. self-assembly on surfaces is driven by the range of interactions between the mols. themselves and the substrate. Generally, a face-on structure is favored for arom. mols. lying flat on the surface. Here, we report on the supramol. self-assembly of 5,10,15,20-tetrakis(10-bromoanthracen-9-yl)porphyrin on the Ag(111) and Ag(110) surfaces. Well-ordered mol. chains were obsd. by room-temp. scanning tunneling microscopy on both surfaces. The relatively small size of the unit cell revealed an edge-on configuration of the porphyrin macrocycles, i.e., perpendicular to the surface plane, as confirmed by mol. mechanics calcns. Distinct intermol. interactions were found on the two surfaces, providing different mol. chain orientations on Ag(111) and Ag(110).
    62. 62
      Mishra, S.; Yao, X.; Chen, Q.; Eimre, K.; Gröning, O.; Ortiz, R.; Di Giovannantonio, M.; Sancho-García, J. C.; Fernández-Rossier, J.; Pignedoli, C. A.; Müllen, K.; Ruffieux, P.; Narita, A.; Fasel, R. Large Magnetic Exchange Coupling in Rhombus-Shaped Nanographenes with Zigzag Periphery. Nat. Chem. 2021, 13, 581– 586,  DOI: 10.1038/s41557-021-00678-2
      62
      Large magnetic exchange coupling in rhombus-shaped nanographenes with zigzag periphery
      Mishra, Shantanu; Yao, Xuelin; Chen, Qiang; Eimre, Kristjan; Groning, Oliver; Ortiz, Ricardo; Di Giovannantonio, Marco; Sancho-Garcia, Juan Carlos; Fernandez-Rossier, Joaquin; Pignedoli, Carlo A.; Mullen, Klaus; Ruffieux, Pascal; Narita, Akimitsu; Fasel, Roman
      Nature Chemistry (2021), 13 (6), 581-586CODEN: NCAHBB; ISSN:1755-4330. (Nature Portfolio)
      Nanographenes with zigzag edges are predicted to manifest non-trivial π-magnetism resulting from the interplay of concurrent electronic effects, such as hybridization of localized frontier states and Coulomb repulsion between valence electrons. This provides a chem. tunable platform to explore quantum magnetism at the nanoscale and opens avenues towards org. spintronics. The magnetic stability in nanographenes is thus far greatly limited by the weak magnetic exchange coupling, which remains below the room-temp. thermal energy. Here, we report the synthesis of large rhombus-shaped nanographenes with zigzag peripheries on gold and copper surfaces. Single-mol. scanning probe measurements show an emergent magnetic spin singlet ground state with increasing nanographene size. The magnetic exchange coupling in the largest nanographene (C70H22, contg. five benzenoid rings along each edge), detd. by inelastic electron tunnelling spectroscopy, exceeds 100 meV or 1,160 K, which outclasses most inorg. nanomaterials and survives on a metal electrode.
    63. 63
      Stöckl, Q. S.; Hsieh, Y.-C.; Mairena, A.; Wu, Y.-T.; Ernst, K.-H. Aggregation of C70-Fragment Buckybowls on Surfaces: π–H and π–π Bonding in Bowl Up-Side-Down Ensembles. J. Am. Chem. Soc. 2016, 138, 6111– 6114,  DOI: 10.1021/jacs.6b02412
      63
      Aggregation of C70-Fragment Buckybowls on Surfaces: π-H and π-π Bonding in Bowl Up-Side-Down Ensembles
      Stockl, Quirin S.; Hsieh, Ya-Chu; Mairena, Anais; Wu, Yao-Ting; Ernst, Karl-Heinz
      Journal of the American Chemical Society (2016), 138 (19), 6111-6114CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      The self-assembly of the C38H14-buckybowl, a fragment bowl of the C70 fullerene, has been studied with scanning tunneling microscopy on the Cu(111) surface. Isolated mols. adsorb bowl opening-up with the center C6 ring parallel to the surface. In extended 2D islands, however, 1/3 of the mols. are oriented such that the bowl opening points down. From a detailed anal. of relative orientation of the mols., the nature of intermol. lateral interactions is identified. In densely packed islands, π-π bonding between convex sides of the bowls dominate, while π-H bonding between rim and convex sides plays the important role in small mol. 2D clusters.
    64. 64
      Wang, T.; Zhu, J. Confined On-Surface Organic Synthesis: Strategies and Mechanisms. Surf. Sci. Rep. 2019, 74, 97– 140,  DOI: 10.1016/j.surfrep.2019.05.001
      64
      Confined on-surface organic synthesis: Strategies and mechanisms
      Wang, Tao; Zhu, Junfa
      Surface Science Reports (2019), 74 (2), 97-140CODEN: SSREDI; ISSN:0167-5729. (Elsevier B.V.)
      A review. On-surface synthesis has been one of the hottest research fields in surface science in the last decade, owing to its great potential for bottom-up synthesis of functional mols. and covalent nanomaterials. Compared to classical in-soln. chem., all of the on-surface reactions are done without solvent, thus very minimal byproducts and no limitation of soly. are involved. However, because of its typically required ultra-high vacuum conditions, where only limited catalysts can be used, a key challenge for on-surface synthesis is the precise control of the reaction pathway. Countless efforts have been made for controllable synthesis of target chem. structures on surfaces by distinct strategies. These strategies can be summarized under following aspects: (1) rational choice of surfaces; (2) template effects based on two-dimensional (2D) environments; (3) on-surface thermodn. and kinetic controls; (4) the participation of chemisorbed nonmetal adatoms on surfaces. This report reviews the recent progress toward the control of on-surface synthesis and raises a series of questions at the end, which deserve further explorations in the future.
    65. 65
      Cai, Z.; She, L.; He, Y.; Wu, L.; Cai, L.; Zhong, D. Halogen-Free On-Surface Synthesis of Rylene-Type Graphene Nanoribbons. Macromol. Chem. Phys. 2017, 218, 1700155  DOI: 10.1002/macp.201700155
      There is no corresponding record for this reference.
    66. 66
      Klaasen, H.; Liu, L.; Meng, X.; Held, P. A.; Gao, H.-Y.; Barton, D.; Mück-Lichtenfeld, C.; Neugebauer, J.; Fuchs, H.; Studer, A. Reaction Selectivity in On-Surface Chemistry by Surface Coverage Control─Alkyne Dimerization versus Alkyne Trimerization. Chem. - Eur. J. 2018, 24, 15303– 15308,  DOI: 10.1002/chem.201802848
      There is no corresponding record for this reference.
    67. 67
      Fesser, P.; Iacovita, C.; Wäckerlin, C.; Vijayaraghavan, S.; Ballav, N.; Howes, K.; Gisselbrecht, J.-P.; Crobu, M.; Boudon, C.; Stöhr, M.; Jung, T. A.; Diederich, F. Visualizing the Product of a Formal Cycloaddition of 7,7,8,8-Tetracyano-p-Quinodimethane (TCNQ) to an Acetylene-Appended Porphyrin by Scanning Tunneling Microscopy on Au(111). Chem. - Eur. J. 2011, 17, 5246– 5250,  DOI: 10.1002/chem.201100733
      67
      Visualizing the Product of a Formal Cycloaddition of 7,7,8,8-Tetracyano-p-quinodimethane (TCNQ) to an Acetylene-Appended Porphyrin by Scanning Tunneling Microscopy on Au(111)
      Fesser, Petra; Iacovita, Cristian; Waeckerlin, Christian; Vijayaraghavan, Saranyan; Ballav, Nirmalya; Howes, Kara; Gisselbrecht, Jean-Paul; Crobu, Maura; Boudon, Corinne; Stoehr, Meike; Jung, Thomas A.; Diederich, Francois
      Chemistry - A European Journal (2011), 17 (19), 5246-5250, S5246/1-S5246/48CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      We have introduced formal [2+2] cycloaddns. as a click-type on-surface reaction yielding push-pull substituted chromophores with notable optoelectronic properties. High-resoln. low-temp. STM images and manipulations, as well as XPS and ToF-SIMS anal. demonstrate that the reaction occurs on Au(111) and XPS indicates a significant intramol. charge transfer in the product porphyrin. The presented combination of thorough studies of the TCNQ addn. to acetylene-appended porphyrin in soln., in the solid state, and on Au(111) contributes to a methodol. and target-oriented approach towards novel on-surface reactions.
    68. 68
      Franke, M.; Marchini, F.; Steinrück, H.-P.; Lytken, O.; Williams, F. J. Surface Porphyrins Metalate with Zn Ions from Solution. J. Phys. Chem. Lett. 2015, 6, 4845– 4849,  DOI: 10.1021/acs.jpclett.5b02218
      68
      Surface Porphyrins Metalate with Zn Ions from Solution
      Franke, Matthias; Marchini, Florencia; Steinrueck, Hans-Peter; Lytken, Ole; Williams, Federico J.
      Journal of Physical Chemistry Letters (2015), 6 (23), 4845-4849CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      Controlling the metalation of surface porphyrins is a crit. process in porphyrin-based devices. Indeed, surface porphyrins are known to metalate in ultrahigh vacuum from codeposited metal atoms or substrate atoms; however, it is not yet known if surface porphyrins could metalate from ions in soln., i.e., the most likely environment for porphyrin-based devices. Using XPS the authors have studied the metalation of monolayers and multilayers of a free-base tetra-Ph porphyrin adsorbed on Au(111) with ions in soln. Full metalation with Zn2+ can be achieved already at room temp. in contrast with the elevated temps. required for metalation with codeposited metal atoms.
    69. 69
      Herritsch, J.; Kachel, S. R.; Fan, Q.; Hutter, M.; Heuplick, L. J.; Münster, F.; Gottfried, J. M. On-Surface Porphyrin Transmetalation with Pb/Cu Redox Exchange. Nanoscale 2021, 13, 13241– 13248,  DOI: 10.1039/D1NR04180K
      69
      On-surface porphyrin transmetalation with Pb/Cu redox exchange
      Herritsch, Jan; Kachel, Stefan R.; Fan, Qitang; Hutter, Mark; Heuplick, Lukas J.; Muenster, Florian; Gottfried, J. Michael
      Nanoscale (2021), 13 (31), 13241-13248CODEN: NANOHL; ISSN:2040-3372. (Royal Society of Chemistry)
      Metal complexes at surfaces and interfaces play an important role in many areas of modern technol., including catalysis, sensors, and org. electronics. An important aspect of these interfaces is the possible exchange of the metal center, because this reaction can drastically alter the properties of the metal complex and thus of the interface. Here, we demonstrate that such metal exchange reactions are indeed possible and can proceed already at moderate temps. even in the absence of solvents. Specifically, we studied the redox transmetalation of a monolayer of lead(II)-tetraphenylporphyrin (PbTPP) with copper from a Cu(111) surface under ultrahigh-vacuum (UHV) conditions using multiple surface-sensitive techniques. Temp.-dependent XPS reveals that the Pb/Cu exchange starts already below 380 K and is complete at 600 K. The identity of the reaction product, CuTPP, is confirmed by mass spectrometric detection in a temp.-programmed reaction (TPR) expt. Scanning tunneling microscopy (STM) sheds light on the adsorbate structure of PbTPP at 300 K and uncovers the structural changes accompanying the transmetalation and side-reactions of the Ph substituents. Moreover, individual free Pb atoms are obsd. as a product of the metal exchange.
    70. 70
      Hötger, D.; Abufager, P.; Morchutt, C.; Alexa, P.; Grumelli, D.; Dreiser, J.; Stepanow, S.; Gambardella, P.; Busnengo, H. F.; Etzkorn, M.; Gutzler, R.; Kern, K. On-Surface Transmetalation of Metalloporphyrins. Nanoscale 2018, 10, 21116– 21122,  DOI: 10.1039/C8NR04786C
      70
      On-surface transmetalation of metalloporphyrins
      Hotger Diana; Abufager Paula; Morchutt Claudius; Alexa Patrick; Grumelli Doris; Dreiser Jan; Stepanow Sebastian; Gambardella Pietro; Busnengo H Fabio; Etzkorn Markus; Gutzler Rico; Kern Klaus
      Nanoscale (2018), 10 (45), 21116-21122 ISSN:.
      Increasing the complexity of 2D metal-organic networks has led to the fabrication of structures with interesting magnetic and catalytic properties. However, increasing complexity by providing different coordination environments for different metal types imposes limitations on their synthesis if the controlled placement of one metal type into one coordination environment is desired. Whereas metal insertion into free-base porphyrins at the vacuum/solid interface has been thoroughly studied, providing detailed insight into the mechanisms at play, the chemical interaction of a metal atom with a metallated porphyrin is rarely investigated. Herein, the breadth of metalation reactions is augmented towards the metal exchange of a metalloporphyrin through the deliberate addition of atomic metal centers. The cation of Fe(ii)-tetraphenylporphyrins can be replaced by Co in a redox transmetalation-like reaction on a Au(111) surface. Likewise, Cu can be replaced by Co. The reverse reaction does not occur, i.e. Fe does not replace Co in the porphyrin. This non-reversible exchange is investigated in detail by X-ray absorption spectroscopy complemented by scanning tunneling microscopy. Density functional theory illuminates possible reaction pathways and leads to the conclusion that the transmetalation proceeds through the adsorption of initially metallic (neutral) Co onto the porphyrin and the expulsion of Fe towards the surface accompanied by Co insertion. Our findings have important implications for the fabrication of porphyrin layers on surfaces when subject to the additional deposition of metals. Mixed-metal porphyrin layers can be fabricated by design in a solvent-free process, but conversely care must be taken that the transmetalation does not proceed as an undesired side reaction.
    71. 71
      Rieger, A.; Schnidrig, S.; Probst, B.; Ernst, K.-H.; Wäckerlin, C. Ranking the Stability of Transition-Metal Complexes by On-Surface Atom Exchange. J. Phys. Chem. Lett. 2017, 8, 6193– 6198,  DOI: 10.1021/acs.jpclett.7b02834
      71
      Stability of transition-metal complexes by on-surface atom exchange
      Rieger, Alexandra; Schnidrig, Stephan; Probst, Benjamin; Ernst, Karl-Heinz; Wackerlin, Christian
      Journal of Physical Chemistry Letters (2017), 8 (24), 6193-6198CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      Surface-adsorbed macrocycles exhibit a no. of interesting phys. and chem. properties; many of them are detd. by their transition-metal centers. The hierarchical exchange of the central metal atom in such surface-adsorbed complexes is demonstrated, specifically in the porphyrin-like macrocycle pyrphyrin adsorbed on Cu(111). Using scanning tunneling microscopy and XPS, we show that Cu as central metal atom is easily exchanged with Ni or Fe atoms supplied in trace amts. to the surface. Atom exchange of Ni centers with Fe atoms also occurs, with moderate yield. These results allow ranking the stability of the surface-adsorbed Cu, Ni, and Fe complexes. The fact that the atom exchange occurs at 423 K shows that surface-adsorbed macrocycles can be surprisingly easily transformed.
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      Loos, M.; Gerber, C.; Corona, F.; Hollender, J.; Singer, H. Accelerated Isotope Fine Structure Calculation Using Pruned Transition Trees. Anal. Chem. 2015, 87, 5738– 5744,  DOI: 10.1021/acs.analchem.5b00941
      72
      Accelerated Isotope Fine Structure Calculation Using Pruned Transition Trees
      Loos, Martin; Gerber, Christian; Corona, Francesco; Hollender, Juliane; Singer, Heinz
      Analytical Chemistry (Washington, DC, United States) (2015), 87 (11), 5738-5744CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
      A fast and memory-efficient calcn. of theor. isotope patterns is crucial for the routine interpretation of mass spectrometric data. For high-resoln. expts., calcns. must procure the exact masses and probabilities of relevant isotopologues over a wide range of polyisotopic compds., while pruning low-probable ones. Here, a novel albeit simple treelike structure is introduced to swiftly derive sets of relevant subisotopologues for each element in a mol., which are then combined to the isotopologues of the full mol. In contrast to existing approaches, transitions via single replacements of the most abundant isotope per element are used in separable tree branches to derive subisotopologues from each other. The underlying transition trees prevent redundant replacements and permit the detection of the most probable isotopologue in a 1st phase. A relative threshold can then be exploited in a 2nd parallelized phase for a precise prepruning of large fractions of the remaining subisotopologues. The gain in performance from such early pruning and the lower variation in the distortion of simulated data using relative rather than abs. thresholds were validated in a large-scale benchmark simulation, unprecedentedly comprising several thousand mol. formulas. Both the algorithm and a wealth of related features are freely available as R-package enviPat and as a user-friendly Web interface.
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      Horcas, I.; Fernández, R.; Gómez-Rodríguez, J. M.; Colchero, J.; Gómez-Herrero, J.; Baro, A. M. WSXM: A Software for Scanning Probe Microscopy and a Tool for Nanotechnology. Rev. Sci. Instrum. 2007, 78, 013705  DOI: 10.1063/1.2432410
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      WSXM: a software for scanning probe microscopy and a tool for nanotechnology
      Horcas, I.; Fernandez, R.; Gomez-Rodriguez, J. M.; Colchero, J.; Gomez-Herrero, J.; Baro, A. M.
      Review of Scientific Instruments (2007), 78 (1), 013705/1-013705/8CODEN: RSINAK; ISSN:0034-6748. (American Institute of Physics)
      In this work we briefly describe the most relevant features of WSXM, a freeware scanning probe microscopy software based on MS-Windows. The article is structured in three different sections: The introduction is a perspective on the importance of software on scanning probe microscopy. The second section is devoted to describe the general structure of the application; in this section the capabilities of WSXM to read third party files are stressed. Finally, a detailed discussion of some relevant procedures of the software is carried out.

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    • Detailed description of ZnBAP/ZnTAP synthesis; overview images; and abundance of fused ZnBAP/ZnTAP molecules; modeled conformations of the native ZnTAP molecule; modeled structures for ZnTAP-20H and ZnTAP-24H molecules, as well as STM imaging parameters (PDF)


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