Spectroelectrochemistry of the dioxygen adduct of an iron(II) C2-capped porphyrin

Abstract

The spectrolectrochemistry of the dioxygen adduct of the iron(II) C₂-capped porphyrin complex [Fe^IIL(B)]{H₂L = 5,10,15,20-tetraphenylporphyrin capped at the o-position of each of the phenyl rings by C₆H₂[C(O)O(CH₂)₂O]₄-1,2,4,5, B = 1-methylimidazole or pyridine} has been studied in both dimethyl sulfoxide and pyridine solutions. In both cases electrooxidation of the adduct produced an unusual spectrum, assigned to a new type of O₂ adduct, [Fe^IIIL(B)(O₂)]⁺. Subsequent electroreduction of the system regenerated the original O₂ adduct, but not in 100% yield, indicating that some dissociation of O₂ had occurred during the redox cycling. This behaviour is discussed in terms of bonding in the Fe–O₂ adducts.