Ruthenium-Based Catalysts for Water Oxidation: Key Role of Carboxy Group as Proton Acceptor
In this work, the mechanism of water oxidation catalyzed by Ru-based complex [Ru(L)]+ (L = 5,5-chelated 2-carboxy-phen, 2,2’;6’,2’’-terpyridine) was studied by density functional theory (DFT) calculations. In [Ru(L)]+, a carboxy group is included in the second coordination sphere and plays an important role in catalytic process. In the oxidation activation stage of water oxidation catalysis, the carboxy group is proposed as the promising proton acceptor to promote proton transfer, which results in the active RuV=O species. Then O‒O bond formation can proceed via water nucleophilic attack (WNA) or oxo-oxo coupling mechanisms. In O2 release stage, similar to oxidation activation process, the carboxy group promotes proton transfer as the promising proton acceptor. In present work, the favorable mechanism is WNA that involves the proton transfer to carboxy group. It is expected that this work provides meaningful information for synthesizing excellent water oxidation catalysts(WOC).