A New Cu(II) Side-on Peroxo Model Clarifies the Assignment of the Oxyhemocyanin Raman Spectrum

The most intense vibrational feature in the UV rR spectrum of oxyhemocyanin is a band at 267−296 cm-1 which has been assigned as either a Cu−Cu stretch or a Cu−N(His)axial stretch. Cu(II)2 side-on peroxo models utilizing bidentate diamine ligand systems retain this vibrational feature, confirming the Cu−Cu stretch assignment. The identity and enhancement behavior of this mode make it an ideal diagnostic of the side-on peroxo Cu2O2 core.