Light-induced electron-transfer reactions involving the tris(2,2'-bipyridine)ruthenium dication and related complexes. I. The bis(2,2'-bipyridine)(diethyl 2,2'-bipyridine-4,4'-dicarboxylate)ruthenium dication

Abstract

Irradiation of the bis(2,2'-bipyridine)(diethyl 2,2'-bipyridine-4,4'- dicarboxylate)ruthenium(II) dication (2c) in water, in the presence of ethylenediaminetetraacetic acid, methyl viologen and a platinum catalyst, produces hydrogen at about one-tenth the rate observed with Ru(bpy)₃²⁺. This decrease is ascribed to electron withdrawal by the ester group in (2c) and to bimolecular quenching of photo-excited (2c) by water (rate constant 9.3 × 10⁴ 1. mol^-1 s^-1), which follows (in ethanol) Stern-Volmer kinetics (K_SV 9.5 x 10^-2 1. mol^-1).