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The kinetics and mechanism of CeIV oxidation of the water oxidation catalyst (bpy)2(H2O)RuIIIORuIII(OH2)(bpy)24+ (1, RuIIIORuIII) have been investigated by UV−visible measurements with application of global analysis. The reaction proceeds by stepwise oxidation of RuIIIORuIII to RuVORuV with oxidation of RuIVORuIII the slow step. RuVORuV has been identified as an intermediate by the appearance of its ClO4- salt as a black suspension in concentrated solutions at 5 °C. It is the key intermediate in water oxidation. The mechanism may involve a bimolecular step and formation of a peroxo-bridged intermediate. Catalytic water oxidation is greatly retarded after just a few catalytic cycles because of anation induced by O2 evolution.
Binstead et al. (Wed,) studied this question.