Syntheses and properties of polymeric imidazole coordinated ferriprotoporphyrin IX in nonaqueous solution

Abstract

The complexes between ferriprotoporphyrin IX derivatives and polymeric imidazoles were studied in nonaqueous solution by electronic absorption spectral and electron spin resonance measurements. Ferriprotoporphyrin IX chloride and the μ-oxodimer of ferriprotoporphyrin IX dimethyl ester were used. It was found that the μ-oxodimer was dissociated into monomeric species in methanol-rich solvents. The ligand coordination numbers with respect to added bases of the former were found to be 2, while those of the latter were 1. However, both complexes gave the low-spin type absorption and electron spin resonance spectra. The coordination structures were affected by the counter anions of the parent ferriporphyrins used. The formation constants were much larger in polymeric imidazole complexes, while the axial coordination numbers were the same in both polymeric and monomeric 2-unsubstituted imidazoles.