Density functional theory calculations on Fe–O and O–O cleavage of ferric hydroperoxide species: Role of axial ligand and spin state

Density functional theory (DFT) calculations are performed on thiolate bound hydroperoxide complexes. O–O and Fe–O cleavage reaction coordinates, relevant to the active sites of cytochrome P450 and superoxide reductase enzymes, were investigated for both high and low spin states and for cis and trans orientations of the thiolate ligand with respect to the hydroperoxide ligand. The results indicate that the presence of a thiolate ligand produces significant elongation of the Fe–O bond and reduction of Fe–O vibrational frequency. While the fate of the O–O cleavage reaction is not significantly altered, the presence of a thiolate induces a heterolytic Fe–O cleavage irrespective of the spin state and orientation which is very different from results obtained with a trans ammine ligand.