The photoreduction of [Ru(bpy)3]3+ investigated by two-pulse two-colour laser-flash photolysis

The title reaction turns the photoionization of the metal-to-ligand charge-transfer state MLCT of the ruthenium(II)-tris-bipyridyl ion into a catalytic cycle of photoinduced water splitting. To isolate that key step from the complex reaction scheme, the metastable oxidized form OX, [Ru(bpy)3]3+, is prepared by a first laser flash, and then photoreduced by a second. An analysis is presented that yields the efficiency η of the photoreduction from the intensity dependences of the concentrations of MLCT and OX. When water is the donor, η is only about 0.5; for alcohols (1-butanol, 2-propanol, tert-butanol) it is 1.