Increased Light-Harvesting in Dye-Sensitized Solar Cells through Förster Resonance Energy Transfer within Supramolecular Dyad Systems

Novel pyridine-substituted subphthalocyanines were prepared for an additional harvesting of a green spectral region of the solar light spectrum for zinc phthalocyanine-based dye-sensitized solar cells. These compounds can bind with the central metal of zinc phthalocyanines to form the corresponding supramolecular complexes as monitored by the absorption and fluorescence spectral changes. The stability constants of these complexes were altered by the number and position of pyridine units in the pyridine-substituted subphthalocyanines. On the basis of fluorescence titration study, the complexes efficiently transfer energy from the subphthalocyanine to zinc phthalocyanine. The solar cells using TiO₂ electrodes stained with the supramolecular complexes, composed of zinc phthalocyanine sensitizer and pyridine-substituted subphthalocyanines, showed panchromatic responses, and the photocurrent generation in the range of 500–600 nm is attributed to the efficient Förster resonance energy transfer from subphthalocyanine to zinc phthalocyanine on the TiO₂ surface

Catalytic Oxidation of Thiols within Cavities of Phthalocyanine Network Polymers

Two three-dimensional (3D) network polymers (<b>1</b> and <b>2</b>), in which zinc­(II) or cobalt­(II) phthalocyanines were interconnected with twisted 9,9′-spirobifluorene linkers, were synthesized in order to investigate their performance as heterogeneous catalysts for thiol oxidations. From the spectroscopic analyses of two dimers (<b>3</b> and <b>4</b>) as component units of the network polymers, <b>3</b> connected with a short linker revealed electronic interaction between the two phthalocyanine units. Micrometer-sized polymer particles were formed due to the condensation of the twisted 9,9′-spirobifluorene linkers in the presence of zinc or cobalt ions. The dispersed solutions of <b>1</b> and <b>2</b> had sharp Q-bands, indicating the prevention of stacking among phthalocyanine moieties within the polymers. Powdered X-ray diffraction pattern and N₂ adsorption–desorption analyses suggested that <b>1</b> created small and rigid cavities as compared with <b>2</b> through the regular spatially arrangement of the phthalocyanine moieties in the 3D networks. The photocatalytic and catalytic activities of <b>1</b> and <b>2</b> for thiol oxidations using molecular oxygen were examined. We found that the catalytic activity of <b>1</b> was higher than that of <b>2</b> having larger cavities