A study of cobalt(II) porphyrins on their oxygen-binding behaviors and oxygen-facilitated transport properties in polymeric membranes

The oxygen-binding behaviors of five cobalt(II) meso-tetrakis(substituted phenyl)porphyrin complexes [CoTPP, CoT(2-Cl)PP, CoT(4-Cl)PP, CoT(4-MeO)PP, and CoT(2,4-2MeO)PP] in chloroform solution were investigated using a UV-visible spectrophotometer. It shows that the substituents and the fifth ligand in the cobalt(II) porphyrins strongly influence the oxygen-binding rate. The cobalt(II) porphyrin complexes substituted with an electron-donating group on the meso-phenyl ring increase the oxygen-binding rate, in contrast, the cobalt(II) porphyrin complexes substituted with an electron-accepting group decrease the oxygen-binding rate; as fifth ligand, both imidazole and pyridine enhance the oxygen-binding rate of cobalt porphyrin complexes, and the imidazole has a higher oxygen-binding rate. Meanwhile, the oxygen-facilitated transport properties in ethyl cellulose (EC) membranes containing five cobalt porphyrins as oxygen carriers were studied, too. The oxygen-facilitated transport in a membrane containing such complexes could be strongly affected by the different substituents and fifth ligand of the complexes.