Oxygen binding to cobalt porphyrins

Abstract

The thermodynamic constants of oxygen binding to cobalt "picket fence" porphyrin complexes, mejo-tetra(a,a,a,ao-pivalamidophenyl)porphyrinatocobalt(II)-1 -methylimidazole and 1,2-dimethylimidazole, are reported. In contrast to previously studied cobalt porphyrins, these complexes bind oxygen with the same affinity as cobalt substituted myoglobin and hemoglobin. 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.

Unusual oxygen affinity of linear polyvinyl amine–cobalt complexes with hydroxyl counter ions: an efficient way of separation and chemical storage of molecular oxygen

“…[2] Those investigations showed that an additional electron donating ligand so-called 'axial ligand' is essential for efficient binding of oxygen. Later investigations revealed that reversible oxygenation behavior is not confined to Co(II) complexes of salicylaldimine, but many other Co(II) complexes such as ethylenediamine-bridged bis-β-diketones, [3] porphyrins, [4] and cyclams [5] can bind molecular oxygen to give 1:1 or 2:1 oxygen adducts depending on nature [6] and steric effects [7] of the ligating groups.…”

N-Heterocyclic carbene bonding to cobalt porphyrin complexes

“…Porphyrins appear particularly attractive for this purpose [16], as they stabilize the diamagnetic cobalt(III) center and prevent undesired redox-processes at the metal [17]. In addition, coordination of a NHC leaves one labile coordination site opposite to the carbene, which should eventually allow the strong trans effect of the NHC ligand to be exploited.…”

Microporous Porphyrin Solids

“…1 Our interest in this area goes back some 30 years to our studies of reversible O 2 binding in porous molecular solids of picket-fence metalloporphyrins [2][3][4] and especially our adventitious discovery of cooperativity in such binding for several such solids. 5,6 Planning and prediction of the structures of molecular solids, however, is notoriously difficult.…”