tetraphenylporphyrin derivative having two pockets on both sides of the porphyrin ring plane, 5,10,15-tri(2′,6′-bis(pivaloyloxy)phenyl)-20-((2′-hydroxy-6′-pivaloyloxy)phenyl)porphine, and its iron complex were synthesized. The 1,2-dimethylimidazole binding to the iron(II) was enhanced by the presence of a steric-hindrance reduced pocket. The complex formed a stable dioxygen adduct in toluene at 25°C.