Breaking aggregation in a tetrathiafulvalene-fused zinc porphyrin by metal–ligand coordination to form a donor–acceptor hybrid for ultrafast charge separation and charge stabilization

Abstract

A novel electron rich, tetrathiafulvalene fused zinc porphyrin, (TTF)4PZn, has been newly synthesized and characterized using spectral and electrochemical methods. In spite of the presence of eight t-butyl groups, (TTF)4PZn exhibited appreciable aggregation in solution. Scanning electron microscopic (SEM) imaging of the aggregates revealed their spherical particulate morphology. Attenuation of intermolecular aggregation was possible by metal-ligand coordination of a nitrogenous ligand. Further, using this strategy, a donor-acceptor hybrid was formed by coordinating imidazole functionalized fullerene as an electron acceptor. The occurrence of intrasupramolecular ultrafast photoinduced charge separation has been established using fluorescence and transient absorption spectroscopic techniques. The determined rate of charge separation, kCS, and rate of charge recombination, kCR were found to be 1.4 × 10(11) s(-1) and 2.5 × 10(6) s(-1), respectively. The lower kCR values indicate charge stabilization in the assembled donor-acceptor conjugate via an electron transfer-hole transfer mechanism.

Design and photochemical study of supramolecular donor–acceptor systems assembled via metal–ligand axial coordination

“…al. [113] designed an electron rich tetrathiafulvalene fused zinc porphyrin, (TTF) 4 ZnP, as a donor that revealed appreciable self-aggregation (see Fig. 24 for structure).…”

Photocurrent in Multilayered Assemblies of Porphyrin–Fullerene Covalent Dyads: Evidence for Channels for Charge Transport

“…Porphyrin-fullerene (PF) blends, [1][2][3][4][5][6][7][8][9] supramolecular complexes [9][10][11][12][13][14][15][16] and covalently linked ensembles [6,[17][18][19][20][21][22][23][24][25][26] are regarded as possible photoactive materials for solar energy conversion. Porphyrin-fullerene blendsh ave been mostly studied as materials for photovoltaic devices, [1-4, 6, 9] whereas supramolecular complexes and covalently linked ensembles have attracted more interest as artificial photosynthesis models.…”

“…Porphyrin-fullerene blendsh ave been mostly studied as materials for photovoltaic devices, [1-4, 6, 9] whereas supramolecular complexes and covalently linked ensembles have attracted more interest as artificial photosynthesis models. [12][13][14][15][16][17][18][19][22][23][24][25] This discrepancy in applications might be due to the common sense notion that in ap hotovoltaic cell the electron donora nd the electron acceptor should constitute two different phases. This can be easily realized using porphyrin-fullereneb lends, either in the form of two different layersf or the donor (porphyrin) and acceptor( fullerene)c omponents in bilayer cells [5] or in the form of ab icontinuous network of donor and acceptor components in bulk heterojunction (BHJ) devices.…”

“…Porphyrin–fullerene (PF) blends, supramolecular complexes and covalently linked ensembles are regarded as possible photoactive materials for solar energy conversion. Porphyrin–fullerene blends have been mostly studied as materials for photovoltaic devices, whereas supramolecular complexes and covalently linked ensembles have attracted more interest as artificial photosynthesis models . This discrepancy in applications might be due to the common sense notion that in a photovoltaic cell the electron donor and the electron acceptor should constitute two different phases.…”

Tetrathiafulvalene- (TTF-) Derived Oligopyrrolic Macrocycles

“…Compound 32 is another TTF-annulated porphyrin. It was synthesized with a view toward exploring whether deaggregation could be achieved by metal–ligand coordination within a donor–acceptor-based hybrid supramolecule . In dimethyl sulfoxide (DMSO)/D 2 O solution, porphyrin 32 exhibits appreciable aggregation (due to the presence of phenolic −OH groups at the periphery) and gives rise to spherical particulate morphologies, as inferred from scanning electron microscopy (SEM) studies (Figure ).…”