Synthesis of Hyperbranched Polymers with Rhenium(I) Bis(Stilbazoylimino)Acephthalene Complexes at the Branching Units

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Two hyperbranched polymers that contains chlorotricarbonyl rhenium(I) bis(stilbazoylimino)acenaphthene complexes were synthesized. The AB2 typed monomers are based on 3- or 4-stilbazoylimino groups that coordinated to the rhenium center as the bidentate ligands. Self-polymerization could be initiated by the addition of silver triflate that activated the rhenium center by removing the chloride ligand. The sizes of the polymers were studied by various methods including gel permeation chromatography and light scattering, and atomic force microscopy. Addition of electrolyte to the polymer solutions resulted in decrease in molecular size, but after a critical concentration (ca. 10 mM), the sizes increased due to the formation of aggregates. These polymers were fabricated into multilayer films by the layer-by-layer electrostatic self-assembly with another polyanion. The multilayer films could function as the active layer in photovoltaic cells. The open-circuit voltage, short circuit current, and fill factor of the best device were measured to be 0.62 V, 3.7 μA/cm2, and 0.17, respectively. The power conversion efficiencies of the cells were in the order of 10−4 %. The contribution of metal complex in the photosensitization process was confirmed by the plot of incident photon-to-electron conversion efficiency as the function of incident light wavelength.