Resonance Raman studies of the electronic state of oxygen in hemerythrin.

Excitation of oxyhemerythrin with radiation within the envelope of its strong oxygen --> iron chargetransfer band generates two Raman frequencies, at 844 cm(-1) and 500 cm(-1). These are assigned to O-O and Fe-O stretching modes. Confirmation of these assignments is provided by the observed shifts in frequency when (16)O(2) is substituted by (18)O(2) as ligand. Comparison of the position of the 844-cm(-1) band with band positions of small molecules of known oxidation state clearly establishes that the bound oxygen is in an O(2) (2-), peroxide-type, electronic state.