PHOTOINDUCED ELECTRON-TRANSFER REACTION BETWEEN [CU(DMP)P-2](-) (P=PPH(3) OR PPH(2)(M-C6H4SO3-) AND VIOLOGEN DERIVATIVES(OR)

The copper(I) complex, [Cu(dmp)P-2](+or-) (dmp = 2,9-dimethyl-1,10-phe nanthroline, P = triphenylphosphine PPh(3) or diphenylphosphinobenzene -m-sulfonate PPh(2)(m-C6H4SO3-)), catalytically photoreduces viologen derivatives, dicationic methyl viologen MV(2+) and neutral propylviolo gen disulfonate PVS0. The quantum yield phi(V-.) for the viologen phot oreduction is discussed on the basis of the lifetime of the photosensi tiser, formation of the encounter complex, dissociation of the encount er complex to products, and back electron transfer in the encounter co mplex. When [Cu(dmp){PPh(2)(m-C6H4SO3)}(2)](-) is used for the photore duction of MV(2+), the highest quantum yield (phi(V-.)(Tr)=0.03) is ob tained. Kinetic analysis and measurements of the excited state lifetim e reveal that this best phi(V-.) value arises from the rapid formation of the encounter complex, owing to the attractive electrostatic inter action between anionic [Cu(dmp){PPh(2)(m-C6H4SO3)}(2)](-) and cationic MV(2+).