Nuclear Magnetic Resonance Studies of Axial Amine Coordination in Synthetic Ferryl, (FeIVO)2+, Porphyrin Complexes and in Ferryl Myoglobin

Article abstract of DOI:10.1021/ja00297a001

Proton and deuterium NMR studies have detected resonances of coordinated pyridine, 1-methylimidazole, and their derivatives on synthetic ferryl, (Fe^IVO)²⁺, porphyrin complexes.The resonances have been identified through methyl and deuterium labeling.Only one amine ligand is present and it must exchange slowly with the free ligand.The results for these synthetic model complexes have led to the detection of broad, weak axial histidine resonances at -11 and -16 ppm in ferryl myoglobin at 35 deg C.Analysis of the hyperfine shifts in these paramagnetic molecules suggests that the axial amine is located trans to a strongly ?-donating oxo ligand in both the model compounds and ferryl myoglobin.