Key Words: electrochemistry – molecular catalysis – operando spectroscopy – reductive activation of O2

Context: Oxidation chemistry in industrial processes constitutes a multimegaton commodity production valuing tens of billions dollars. The current economic and environmental contexts require to urgently replace the energy-demanding and harmful technologies often used with economically viable and environmentally sound alternatives.[i] Through the reductive activation of O2, metalloenzymes, such as heme and nonheme Fe oxygenases achieve efficient and selective oxygenations by unravelling O2 oxidizing power. This is achieved through partial and controlled reduction of O2 bound at the Fe active site, involving sequential e- and H+ transfers to the Fe-oxygen adduct and formation of various oxidizing intermediates during the catalytic cycle.[ii] We have developed an electrochemical reductive O2 activation strategy and succeeded in mimicking the oxygenase activity by using Fe and Mn porphyrins to generate and to characterize various M-oxygen oxidizing species[iii] and to tune their reactivity.[iv] This original approach is part of the development of green electrosynthesis in an effort to electrify homogeneous catalysis.[v] 

Based on our expertise, the present PhD project proposes to generalize this concept to a wider range of substrates both in organic and aqueous media and to focus on the impact of CO2's Lewis acidity. Our objective is to get new and unprecedented knowledge of the electrochemical O2 reductive activation using Fe and Mn catalysts under mild conditions, focusing on the acidic properties of CO2 as co-substrate. Our roadmap includes(1) optimizing and maturing efficient electrocatalytic systems for oxidation of a wide range of organic substrates under homogeneous conditions, (2) deciphering the mechanisms of oxidation reactions and providing spectroscopic signatures (UV-Vis, EPR, IR) for intermediates species (M(OO°), M(OO), M(OOH), M(O), peroxocarbonato M(OOC(O)O) involved in the catalytic process (M = Fe, Mn) and finally (3) transferring the reactivity to heterogeneous conditions at liquid/solid interfaces.

Bibliography: 

[i] P. Anastas, N. Eghbalia Chem. Soc. Rev., 2010, 39, 301-312.

[ii] M. Duo, T. Corona, K. Ray, W. Nam, ACS Cent. Sci.2019, 5, 1, 13-28.

[iii] (a) N. Kostopoulos, C. Achaibou, J.-M. Noël, F. Kanoufi, M. Robert, C. Fave, E. Anxolabéhère-Mallart Inorg. Chem. 2020, 59, 11577-11583 ; (b) N. Kostopoulos, PhD Thesis, 2021, Université Paris Cité.

[iv] (a) N. Kostopoulos, F. Banse, C. Fave, E. Anxolabéhère-Mallart Chem. Comm. 2021, 57, 1198-1201 ; (b) I. Tomczyk, L. Berthonnaud, E. Nubret, F. Banse, C. Fave, E. Anxolabéhère-Mallart, in preparation; (c) L. Berthonnaud, S. Groni, E. Nubret, C. Fave, E. Anxolabéhère-Mallart, in preparation.

[v] (a) S. D. Minteer, P. Baran Acc. Chem. Res.2020, 53, 545-546; (b) J. C. Siu, N. Fu, S. Lin Acc. Chem. Res. 2020, 53, 547-560.