Imidazole ligand effect on O2 interaction with metalloporphyrins

We investigate the imidazole ligand effect on O2 interaction with metalloporphyrins (MPs) using ab initio density functional calculations. We select iron-porphyrin (FeP) and cobalt-porphyrin (CoP) as MPs, and compare MP with (imidazole)MP [(Im)MP] including their O2 adducts. The O-O bond of (Im)MP-O2 tends to be weaker than that of MP-O2 due to more accessible back-donation to O2, resulting from a strong electron push from the imidazole ligand, though the effect is not true for the interaction of excited singlet O2.