Study of photoinduced electron transfer of tris(phenothiazine) subphthalocyanine-fullerene pentad for light energy harvesting system
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Abstract
Photo induced excitation and electron transfer to reaction center generate long lived charge separated state is the key step for natural photosynthesis process in green plants to harvest light energy. Well-arranged donor and acceptor systems play a vital role in this field. By mimicking particularly the photo induced process of natural photosynthesis, efficient supramolecular assemblies based on donor and acceptors has been designed and studied. In present study a pentad of Subphthalocyanine (SubPc) as an electron donor that comprises an axially covalently linked fullerene as an acceptor has been synthesized for a model compound to mimic natural photosynthesis. The subphthalocyanine moiety has been peripherally functionalized with three phenothiazine (PHZ) substituents to facilitate the electron transfer event between donor and acceptor. Upon photo excitation at 575nm band of SubPc, photoinduced electron transfer to fullerene occurs which is followed by the hole transfer from SubPc to phenothiazine molecules. Thus, a long lived charge separated state PHZ•+SubPc-C60•- has been achieved with a lifetime of 185ns. Occurrences of charge separated state have been witnessed in the pentad from the femtosecond and nanosecond transient absorption studies.