Catalytic Water Oxidation by a Bio-inspired Nickel Complex with a Redox-Active Ligand.

The oxidation of water (HO) to dioxygen (O) is important in natural photosynthesis. One of nature's strategies for managing such multi-electron transfer reactions is to employ redox-active metal-organic cofactor arrays. One prototype example is the copper tyrosinate active site found in galactose oxidase. In this work, we have implemented such a strategy to develop a bio-inspired nickel phenolate complex capable of catalyzing the oxidation of HO to O electrochemically at neutral pH with a modest overpotential. Employment of the redox-active ligand turned out to be a useful strategy to avoid the formation of high-valent nickel intermediates while a reasonable turnover rate (0.15 s) is retained.