The catalytic conversion of carbon dioxide into valuable chemical feedstocks and synthetic fuels is a critical challenge towards achieving sustainable, carbon-neutral, technologies. As such, the electrocatalytic reduction of CO2 to CO utilizing renewable sources is a highly studied field of research. Our current understanding of electrocatalytic CO2 reduction with homogeneous molecular transition metal catalysts has progressed significantly in recent years, yet multiple challenges still remain. For example, taking advantage of proton-coupled electron transfer (PCET) phenomena, by the engineering of a second coordination sphere in the catalyst, may promote access to a lower energy transition state structure thereby lowering the catalyst overpotential. In this study, both the inner coordination sphere and second coordination sphere of the manganese(I) polypyridyl tricarbonyl class of catalyst is investigated. Specifically, the [fac-Mn(dpa)(CO)3(CH3CN)](OTf) pre-catalyst is presented, where dpa is the k2-2,2’-dipyridylamine. In contrast to the benchmark bpy ligand, dpa forms a 6-membered metallacycle at the Mn(I) center with an inner coordination sphere closer to ideal octahedral geometry. Furthermore, the dpa ligand possesses a bridging secondary amine group in the equatorial plane with potential to participate as a Brønsted base at the critical rate-determining C–OH bond cleavage transition state en-route to CO production. A comprehensive evaluation of the [fac-Mn(dpa)(CO)3(CH3CN)](OTf) complex will be here presented encompassing structural, electrochemical, electrocatalytic and computational characterization.

Electrocatalytic CO2 reduction by [fac-Mn(dpa)(CO)3(CH3CN)](OTf)

ACS Spring 2022

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