Electronic Structure Contributions to the Reactivity of Mononuclear Fe^IV-Oxo Intermediates

ConspectusMononuclear iron enzymes can perform oxidative chemistry that is key to many biological processes, including natural product biosynthesis, DNA repair, and bioremediation. Fe^IV-oxo intermediates are often the active species responsible for this reactivity, as these can abstract an H atom from strong C-H bonds in organic substrates, initiating catalysis.Chemists have been inspired by these remarkable intermediates for more than 40 years and have synthesized a wide range of biomimetic Fe^IV═O complexes with either S = 1 or S = 2 spin ground states that can react with organic substrates. However, no consensus exists in terms of which are the most reactive species because the steric hindrance that is necessary for the stability of these Fe^IV-oxo species also impacts reactivity toward the substrate.This Account provides a methodology to study experimentally the geometric and electronic structures of Fe^IV-oxo active sites and understand their contribution to reactivity. These results provide a rationale for understanding the relative reactivities of Fe^IV═O intermediates in different spin states and with different equatorial ligand fields and can guide the design of new iron-based catalysts for oxidative chemistry.