Adsorption of molecular oxygen by polymer covalently bonded co(II) porhyrin complex in toluene

Abstract

SynopsisReaction between molecular oxygen and polystyrene covalently bonded Co(I1) protoporphyrin IX complex, which was prepared by the incorporation of a cobaltous ion into the metal-free porphyrin polymer, was studied in toluene in the presence of N-ethylimidazole by measuring visible absorption and electron spin resonance spectra. It was found that the complex forms a monomeric oxygen adduct reversibly at low temperature dependent on oxygen pressure. In the presence of molecular oxygen, a new electron spin resonance signal due to the oxygen complex at g i , = 2.02 shows no superhyperfine splitting structure in fluid toluene solution even at -8O"C, but it was observed in frozen toluene glass solution at -120%. The oxygen adducts of the complexes between Co(I1) protoporphyrin IX dimethyl ester and N-ethylimidazole and copoly(styrene-N-vinylimidazole) showed eight resolved superhyperfie splitting a t -40 and -6OoC, respectively. The polymer covalently bonded Co(I1) complex with N-ethylimidazole was oxidized at room temperature under oxygen atmosphere. It was suggested that a Co(I1) porphyrin-oxygen adduct with an axial ligand may be oxidized monomolecularly at higher temperature.