Resonance Raman studies of transition metal complexes containing activated oxygen species

ioxygen is a powerful oxidant that must be activated to release its oxidizing potential. The four-electron reduction of dioxygen is thermodynamically favorable but the triplet ground state of the molecule presents a kinetic barrier to reduction. The kinetic barrier is overcome when dioxygen binds to a reduced transition metal center in a process called oxygen activation. The mechanism of oxygen activation by metalloenzymes and synthetic model complexes is currently the focus of intense study in biochemistry, biophysics, and bioinorganic chemistry. Resonance Raman spectroscopy has proven to be a powerful and generally useful technique for characterizing species involved in oxygen activation, both in metalloenzymes and synthetic model complexes.;Oxygen activation can be assisted by transition metals by direct electron transfer from the metal to dioxygen through an intermediate involving the metal and dioxygen. One such intermediate is the transition metal-peroxide complex. Peroxo and alkylperoxo complexes of iron have been proposed as intermediates in the oxygen activation mechanism. An alkylperoxo complex is thought to be an intermediate in the catalytic cycle of lipoxygenase. Resonance Raman studies of alkylperoxo complexes of iron show that the O-O bond is intact, support the assignment of major feature in the electronic absorption spectrum as a peroxo-to-Fe(III) charge transfer transition, and document a distinctive pattern of vibrations that is diagnostic of an alkylperoxo complex of Fe(III).;The...