Cytochrome P450 monooxygenases (CYP450s) involved in critical biological processes catalyze the incorporation of one atom of molecular oxygen into biological substrates. In such processes, the progression of species formed during catalytic cycles is intermediates that are interrelated by sequential reduction and/or protonation: oxy-heme (i.e., the ferric-superoxide), peroxide and hydroperoxide. Over the years, the generation and spectroscopic characterization of these analogs have been of great interest. In this presentation, we describe the generation of superoxide, peroxide and hydroperoxide analogs using two different heme model complexes through electron reduction and protonation processes and characterization with UV-vis, EPR and resonance Raman spectroscopies. We also report key thermodynamic insights into the transformations involving these metal bound O<sub>2</sub>-derived species: experimentally determined superoxide complex reduction potentials and peroxide ligand basicities. With these new data, we have advanced our understanding of the thermodynamics interrelating these three complex types; OO–H bond dissociation free energies (BDFE’s) of ferric heme hydroperoxide complexes have been calculated. Then, the reactivity results of superoxide species with/without axial ligand with external substrates reveal their oxidizing capability, and these observations corroborate the newly determined thermodynamic results.

Thermochemistry of ferric heme hydroperoxide complexes: Hydrogen atom abstraction reactivity of the superoxide partner complexes

ACS Spring Meeting 2021

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