A Ferromagnetically Coupled (S=1) Peroxodicopper(II) Complex

Copper enzymes play important roles in the binding and activation of dioxygen in biological systems. Key copper/dioxygen intermediates have been identified and studied in synthetic analogues of the metalloprotein active sites, including the -(2):(2)-peroxodicopper(II) motif relevant to typeIII dicopper proteins. Herein, we report the synthesis and characterization of a bioinspired dicopper system that forms a stable -(1):(1)-peroxo complex whose Cu-O-O-Cu torsion is constrained to around 90 degrees by ligand design. This results in sizeable ferromagnetic coupling between the copper(II) ions, which is detected by magnetic measurements and HF-EPR spectroscopy. The new dicopper peroxo system is the first with a triplet ground state, and it represents a snapshot of the initial stages of O-2 binding at typeIII dicopper sites.