The Use of a Vanadium Species As a Catalyst in Photoinduced Water Oxidation

The first water oxidation catalyst containing only vanadium atoms as metal centers is reported. The compound is the mixed-valence [(VIV 5VV 1)O7(OCH3)12]−species, 1. Photoinduced water oxidation catalyzed by 1, in the presence of Ru(bpy)3 2+ (bpy = 2,2′-bipyridine) and Na2S2O8, in acetonitrile/aqueous phosphate buffer takesplace with a quantum yield of 0.20. A hole scavenging reaction between the photochemically generated Ru(bpy)33+ and 1 occurs with a bimolecular rate constant of 2.5 × 108 M−1 s−1. The time-resolved formation of the oxidized molecular catalyst 1+ in bimolecular reactions is also evidenced for the first time by transient absorption spectroscopy. This result opens the way to the use of less expensive vanadium clusters as water oxidation catalysts in artificial photosynthesis schemes.