Synthetic heme dioxygen adducts: electronic structure and reactivity

Heme dioxygen adducts (FeO2) are ubiquitous in all heme-based oxygen activating enzymes, which presents a rather curious case of electronic structure as well as reactivity. They participate in binding/transfer, activation, and reduction of O2 as well as deoxygenation of amino acids. While erstwhile efforts explored these species as models of hemoglobin using a broad range of spectroscopic techniques, recently there have been substantial developments in the understanding of reactivity of these entities. The FeO2 species have been shown to undergo reduction, protonation, and proton coupled electron transfer and perform hydrogen atom transfer and deoxygenation of organic substrates. Both electronic structure and reactivities are strongly affected by the axial ligand to the heme and presence of second sphere hydrogen-bonding interaction.