An electron spin resonance study of the aggregation of copper(II) water-soluble porphyrins

Abstract

Electron spin resonance measurements involving aqueous solutions of copper(II) tetraphenylporphyrintetrasulphonate have been carried out both at room temperature and 77 K to provide evidence for the process of aggregation. The addition of dimethylformamide or dimethyl sulphoxide to the aqueous solution containing the copper(II) chelate results in a breaking up of the polymer units into a distribution of species which include dimeric and monomeric species. The dimeric species are formed only to a minor extent. A similar study of solutions containing the copper(II) chelate of tetracarboxyphenylporphyrin showed that breakdown to monomeric species only occurred in solutions containing a high percentage of dimethylformamide or dimethyl sulphoxide, and that here, too, specific dimeric species did not occur in any great amount. The magnetic parameters have been determined for the monomeric chelates.