A molecular mechanics model of the metalloporphyrins: the role of steric hindrance in discrimination in favour of dioxygen relative to carbon monoxide in some haem models

Abstract

A Molecular Mechanics (M.M.) model of complexes of P^V, Ni^II, Fe^II, Zn^II, and Pb^II with porphyrins is discussed, which predicts with considerable accuracy the bond lengths and angles, and the extent of S₄ ruffling of the porphyrin core as the metal ions are changed; the model suggests that there is a considerable steric contribution to the depression of carbon monoxide relative to dioxygen loading onto capped Fe^II porphyrins.