Electron spin resonance study of the oxygenation of cobalt(II) tetraphenylporphyrintetrasulphonate

Abstract

E.s.r. spectroscopy has been used to show that the addition of NN-dimethylformamide or dimethyl sulphoxide to aqueous solutions of cobalt(II) tetraphenylporphyrintetrasulphonate. [Co^II(tpps)], results in a disaggregation of the metalloporphyrin and provides conditions for its oxygenation by molecular oxygen. Larger additions of ethanol lead to formation of a monomeric six-co-ordinate cobalt(II) porphyrin which does not undergo a reaction with molecular Oxygen to any great extent. On long storage in air, [Co^II(tpps)] in the solid state forms a complex with molecular oxygen. The magnetic parameters associated with the e.s.r. spectra of the monomeric forms of the metalloporphyrin and its complex with molecular oxygen have been determined. The oxygenated complex is believed to involve a Co–O–O bond angle of 105°. intermediate between the two models proposed previously for oxyhaemoglobin.