Molecular Mechanism of the Mononuclear Copper Complex-Catalyzed Water Oxidation from Cluster-Continuum Model Calculations.

Cluster-continuum model calculations were conducted to decipher the mechanism of water oxidation catalyzed by a mononuclear copper complex. Among various O-O bond formation mechanisms investigated in this study, the most favorable pathway involved the nucleophilic attack of OH- onto the .+ L-CuII -OH- intermediate. During such process, the initial binding of OH- to the proximity of .+ L-CuII -OH- would result in the spontaneous oxidation of OH- , leading to OH⋅ radical and CuII -OH- species. The further O-O coupling between OH⋅ radical and CuII -OH- was associated with a barrier of 14.8 kcal mol-1 , leading to the formation of H2 O2 intermediate. Notably, the formation of "CuIII -O.- " species, a widely proposed active species for O-O bond formation, was found to be thermodynamically unfavorable and could be bypassed during the catalytic reactions. On the basis the present calculations, a catalytic cycle of the mononuclear copper complex-catalyzed water oxidation was proposed.