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

A series of water-soluble viologen-linked zinc porphyrins with different me thylene 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 me asured by using fluorescence lifetime and laser flash photolysis. Both the photoexcited singlet state and the triplet state of the porphyrin were quen ched by the bonded viologen. These compounds were applied to photoinduced h ydrogen evolution in the system containing nicotinamide-adenine dinucleotid e phosphate (reduced form NADPH), ZnP(CnV)(4) and hydrogenase under steady- state irradiation. (C) 1998 John Wiley & Sons, Ltd.