Oxidation of water

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We succeeded in catalytic water oxidation using a bis-mu-hydroxo-Co(III)-TPA dimer complex, [CoIII(mu-OH)(TPA)]2(ClO4)4 (1) (TPA = tris(2-pyridylmethyl)amine), as a catalyst. We conducted the catalytic oxidation with a chemical oxidant, [Ru(bpy)3]3+, to observe O2 evolution and excellent stability of 1 under catalytic conditions. Based on detailed electrochemical and isotope-labeling studies, we proposed a plausible reaction mechanism of the catalytic water oxidation by complex 1, where the oxidation process of the two Co(III) centers to give a bis-mu-oxyl dinuclear Co(III) species is the rate-determining step and intramolecular O-O bond formation in the intermediate. Furthermore, we applied the system to photocatalytic water oxidation using a Ru-based photosensitizer and persulfate as an oxidant in borate buffer at pH 9.3. We obtained the maximum TON of the photocatalysis to be 742, together with the highest quantum yield of 88%, for the dioxygen production.