Modeling Heme Peroxidase: Heme Saddling Facilitates Reactions with Hyperperoxides To Form High-Valent Fe -Oxo Species.

Saddle-shaped hemes have been discovered in the structures of most peroxidases. How such a macrocycle deformation affects the reaction of Fe hemes with hydrogen peroxide (H O ) to form high-valent Fe-oxo species remains uncertain. Through examination of the ESI-MS spectra, absorption changes and H NMR chemical shifts, we investigated the reactions of two Fe porphyrins with different degrees of saddling deformation, namely Fe (OETPP)ClO (1 ) and Fe (OMTPP)ClO (1 ), with tert-butyl hydroperoxide (tBuOOH) in CH Cl at -40 °C, which quickly resulted in O-O bond homolysis from a highly unstable Fe -alkylperoxo intermediate, Fe -O(H)OR (2) into Fe -oxo porphyrins (3).