Excited-state electron-transfer quenching by a series of water photoreduction mediators

Abstract

Rate constants k q for the quenching of the excited state of Ru(bipy) 3 2+ by a series of viologen salts having different redox potential E 1 2 have been determined in deaerated aqueous solutions at pH = 5 by laser flash photolysis. The k q values are found to decrease with increasing — E 1 2 and to correlate with the reaction free-energy change Δ G. Such a correlation is shown to be consistent with the Rehm—Weller model for electron-transfer reactions.