High-Spin Fe(IV)-Oxo Porphyrin Complexes in Epoxidation Reaction of Olefin : A CASPT2 Study

High-valent iron (IV)-oxo porphyrin π-cation radical species (P+・) FeIV = O are known as an active intermediate in various enzymatic reactions of cytochrome P450s. In epoxidation reactions catalyzed by these species, potential surfaces between reactant and product are connected by the intersystem crossing. In this report, CASPT2, SO-CASPT2 and SAC-CI calculations were carried out to analyze low-lying doublet, quartet, and sextet electronic ground and excited states in an expoxidation reaction of olefin catalyzed by Cl−(P+・) FeIV = O. In both CASPT2 and SAC-CI calculations, we obtained the quartet and sextet ground states of Cl−(P+・) FeIV = O and Cl (P) FeIII respectively as suggested experimentally.