Dual electron-transfer reactivity of a high-spin iron(III) porphyrin cation radical complex

Abstract

Easily oxidised nucleophiles, such as iodide, bromide, and 1,8-bis(dimethylamino)naphthalene, react with the diaquotetraphenylporphyrinatoiron(III) cation radical complex, [Fe(H₂O)₂(tpp˙)]²⁺, to give the corresponding tetraphenylporphyrin complex, [Fe(H₂O)₂(tpp)]⁺, while pyridine gives an entirely different product, [(tpp)FeOFe(tpp˙)]⁺; e.s.r. spectra and potentiometric evidence suggest that a base-dependent internal electronic isomerisation, leading to tetraphenylporphyrinato-oxoiron(IV), takes place in the latter reaction.