Photoinduced electron transfer reactions of ruthenium(II) complexes containing 2,2′-bipyridine-4,4′-dicarboxylic acid with phenols

Luminescent mixed-ligand ruthenium(II) complexes of type RuLnX3−n (L = 2,2′-bipyridine, X = 2,2′-bipyridine-4,4′-dicarboxylic acid, n = 0,1,2,3) have been synthesized and their photophysical and electrochemical properties are investigated. The emission lifetime measured for RuLnX3−n reveals that the lifetime increases as the ligand L is replaced by X. The luminescence quenching of *RuLnX3−n with several substituted phenolate ions in aqueous medium is efficient and the change of quenching rate data with the change of structure of ligand of RuLnX3−n and phenolate ion is explained in terms of exergonicity of the reaction, electron transfer distance and charge effect. The semiclassical theory of electron transfer has been successfully applied to this photoredox system.