SPECTROELECTROCHEMISTRY OF THE DIOXYGEN ADDUCT OF AN IRON(II) C2-CAPPED PORPHYRIN

The spectroelectrochemistry of the dioxygen adduct of the iron(II) C2-capped porphyrin complex [Fe(II)L(B)] {H-2L = 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(III)L(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.