Iridium(iii) molecular catalysts for water oxidation: the simpler the faster

We report on three Ir(iii) molecular catalysts for water oxidation: 1, [Cp*Ir(ppy)Cl]; 2, [Cp*Ir(bzpy)NO(3)]; 3, [Cp*Ir(H(2)O)(3)](NO(3))(2). 2 and 3 are water-soluble and show a long-term activity ca. 2 and 3 times higher than 1. It is remarkable that 3, having the simplest structure, is the catalyst with the highest activity.