Imidazole and p-Nitrophenolate Complexes of Oxoiron(IV) Porphyrin π-Cation Radicals as Models for Compounds I of Peroxidase and Catalase

The title complexes, (P•)FeIVO(Im) and (P•)FeIVO(OAr), have been prepared by the ozone oxidation of iron(III) porphyrins. The absorption spectra of (P•)FeIVO(Im) and (P•)FeIVO(OAr) are similar to those of compounds I of horseradish peroxidase and catalase, respectively. The NMR measurements of (P•)FeIVO(Im) show an a1u radical state. The absorption spectral features of compound I species reflect the basicity of the axial ligand rather than the HOMO of the porphyrin π-cation radical.