Vitamin B12 (macrocyclic cobalamin) has been recently reported to be capable of electrochemically cat-alyzing water oxidation in a neutral phosphate buffer solution.In this work,density functional calcula-tions were employed to elucidate the water oxidation mechanism catalyzed by vitamin B12.The calcu-lations showed that the catalytic cycle starts from the L·-CoⅡ-OH2 complex 1.A proton-coupled electron transfer process then leads to the formation of a L·-CoⅢ-OH complex 2,followed by another proton-coupled electron transfer event to afford a corrin ligand radical cation intermediate 3 (L·-CoⅢ-O·).The re-dox non-innocent nature of the corrin ligand plays an essential role in the oxidation process.3 is capable of triggering the O-O bond formation via a water nucleophilic attack mechanism,in which a hydrophos-phate dianion functions as a base to accept a proton from the water nucleophile.A dioxygen molecule is released after the oxidation of the CoⅢ-OOH intermediate.The rate-determining step was calculated to be the O-O bond formation with a total barrier of 16.5 kcal/mol.While the use of water molecules as the proton acceptor was found to be less feasible for the O-O bond formation,with a barrier of 31.2 kcal/mol,further highlighting the crucial of phosphate in water oxidation.

Ying-Ying Li;Rong-Zhen Liao

Key Laboratory of Material Chemistry for Energy Conversion and Storage,Ministry of Education,Hubei Key Laboratory of Bioinorganic Chemistry and Materia Medica,Hubei Key Laboratory of Materials Chemistry and Service Failure,School of Chemistry and Chemical Engineering,Huazhong University of Science and Technology,Wuhan 430074,China

中国化学快报（英文版）

[1]Ying-Ying Li;Rong-Zhen Liao-.Mechanism of water oxidation catalyzed by vitamin B12:Redox non-innocent nature of corrin ligand and crucial role of phosphate)[J].中国化学快报（英文版）,2022(01):358-361

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