O2-Adduct Complex of meso-Tetrakis(α,α,α,α-o-pivalamidophenyl)porphinatoiron(II) with an Intramolecularly Coordinated Proximal Histidine

meso-Tetrakis(α,α,α,α-o-pivalamidophenyl)porphinatoiron(II) with an intramolecularly coordinated proximal histidine forms a stable O2-adduct complex in benzene solution at 25 °C; the O2-binding affinity (P1/2: 1.7 Torr) is significantly low compared to that of the N-alkylimidazole bound analogue.