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

Abstract

Magnetic interactions and the nature of the chemical bonds of the biomimetic Cu 2(μ–η 2:η 2–O 2) complexes of oxyhemocyanin and oxytyrosinase have been investigated with hybrid density functional theory. The Cu 2(μ–η 2:η 2–O 2) 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 Cu 2(μ–η 2:η 2–O 2) species. Natural orbital analysis clearly shows that the superexchange interaction of the d xy orbitals of the Cu ions through the π ∗ orbitals of μ–η 2:η 2 peroxide is responsible for the antiferromagnetic couplings of these Cu 2O 2 system and that the distortion of the Cu 2O 2 core from a planar structure to a butterfly structure and elongation of the Cu–O bonds cause the reduction of orbital interactions between the d xy ± d xy orbitals of the dicopper site and the σ ∗ and π ∗ orbitals of peroxide, weakening the magnetic coupling between the Cu sites via μ–η 2:η 2-peroxide.