Heme Cleavage with Remarkable Ease: Paramagnetic Intermediates Formed by Aerobic Oxidation of a Meso-Amino-Substituted Iron Porphyrin

Abstract

Hemes must be oxidatively stable to carry out their functions as biological oxidants, but introduction of a single amino group at a meso position of octaethylheme renders it extremely sensitive to ring opening by dioxygen. Exposure of a red pyridine (py) solution of diamagnetic (py)(2)Fe(II)(H(2)N-OEP) (1) (H(2)N-OEP is the dianion of meso-amino-octaethylporphyrin) to air results in the immediate formation of a green intermediate which is subsequently converted into a second species that has been crystallized and characterized by X-ray diffraction. This process is distinct from coupled oxidation, a model for biological heme cleavage, because it does not require a sacrificial reducing agent to initiate the process.