Theoretical studies of the magnetic couplings and the chemical indices of the biomimetic models of oxyhemocyanin and oxytyrosinase

Magnetic interactions and the nature of the chemical bonds of the biomimetic Cu2(μ–η2:η2–O2) complexes of oxyhemocyanin and oxytyrosinase have been investigated with hybrid density functional theory. The Cu2(μ–η2:η2–O2) species has drawn attention in type III copper proteins because this structure is suggested as an important motif in biological systems. Many synthetic modeling approaches have been performed and greatly developed our understanding of the character of the Cu2(μ–η2:η2–O2) species. Natural orbital analysis clearly shows that the superexchange interaction of the dxy orbitals of the Cu ions through the π∗ orbitals of μ–η2:η2 peroxide is responsible for the antiferromagnetic couplings of these Cu2O2 system and that the distortion of the Cu2O2 core from a planar structure to a butterfly structure and elongation of the Cu–O bonds cause the reduction of orbital interactions between the dxy ± dxy orbitals of the dicopper site and the σ∗ and π∗ orbitals of peroxide, weakening the magnetic coupling between the Cu sites via μ–η2:η2-peroxide.