Photoinduced hydrogen evolution with hydrogenase and water-soluble viologen-linked zinc porphyrins

A series of water-soluble viologen-linked zinc porphyrins with different methylene chain lengths (n = 3-6) between porphyrin and viologen, ZnP(CnV)(4), were synthesized and characterized. The intramolecular electron transfer rate constants from the porphyrin moiety of ZnP(CnV)(4) to viologen were measured by using fluorescence lifetime and laser flash photolysis. Both the photoexcited singlet state and the triplet state of the porphyrin were quenched by the bonded viologen. These compounds were applied to photoinduced hydrogen evolution in the system containing nicotinamide-adenine dinucleotide phosphate (reduced form NADPH), ZnP(CnV)(4) and hydrogenase under steady-state irradiation. (C) 1998 John Wiley & Sons, Ltd.