Calcium-Ion Binding Mediates the Reversible Interconversion of Cis and Trans Peroxido Dicopper Cores.

Coupled dinuclear copper oxygen cores (Cu O ) featured in type III copper proteins (hemocyanin, tyrosinase, catechol oxidase) are vital for O transport and substrate oxidation in many organisms. μ-1,2-cis peroxido dicopper cores ( P) have been proposed as key structures in the early stages of O binding in these proteins; their reversible isomerization to other Cu O cores are directly relevant to enzyme function. Despite the relevance of such species to type III copper proteins and the broader interest in the properties and reactivity of bimetallic P cores in biological and synthetic systems, the properties and reactivity of P Cu O species remain largely unexplored. Herein, we report the reversible interconversion of μ-1,2-trans peroxido ( P) and P dicopper cores. Ca mediates this process by reversible binding at the Cu O core, highlighting the unique capability for metal-ion binding events to stabilize novel reactive fragments and control O activation in biomimetic systems.