Oxygen Binding to Cobalt Porphyrins

Abstract: The thermodynamic constants of oxygen binding to cobalt “picket fence ” porphyrin complexes, meso-tetra(a,o,a,o-o-pivalamidophenyl)porphyrinatocobalt(II)- 1-methylimidazole and 1,2-dimethylimidazole, are reported. In contrast to pre-viously studied cobalt porphyrins, these complexes bind oxygen with the same affinity as cobalt substituted myoglobin and he-moglobin. Solvation effects are discussed as the source of this difference. The use of sterically hindered axial bases as models of T state hemoglobin is discussed. In studies of myoglobin (Mb) and hemoglobin (Hb), the replacement of the neutral iron porphyrin prosthetic group with different metalloporphyrins has proved to be a useful tech