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Dinuclear Cobalt Complexes for Homogeneous Water Oxidation: Tuning Rate and Overpotential Through the Non‐Innocent Ligand

Von Wiley-VCH zur Verfügung gestellt

In this study, dinuclear cobalt complexes ( 1 and 2 ) featuring bisbenzimidazolepyrazolide-type ligands ( H 2 L and Me 2 L ) were prepared and evaluated as molecular electrocatalysts for water oxidation. Notably, 1 bearing a non-innocent ligand ( H 2 L ) displays faster catalytic turnover than 2 under alkaline conditions, and the base dependence of WO and kinetic isotope effect analysis indicate that the reaction mediated by 1 proceeds by a different mechanism relative to 2 . Spectroelectrochemical, cold-spray ionization mass spectrometry, and computational studies found that double deprotonation of 1 under alkaline conditions cathodically shifts the catalysis-initiating potential and further alters the turnover-limiting step from nucleophilic water attack on ( H 2 L )Co III 2 (superoxo) to deprotonation of ( L )Co III 2 (OH) 2 . The rate-overpotential analysis and catalytic Tafel plots show that 1 exhibits a significantly higher rate than previously reported Ru-based dinuclear electrocatalysts at similar overpotentials. These observations suggest that using non-innocent ligands is a valuable strategy for designing effective metal-based molecular WOCs.

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