First row transition metal photocatalysts for CO2 reduction: Exploitation of a long-lived excited state for self-sensitized catalysis

Abstract: We have had a long-standing interest in designing new catalysts for CO2 reduction using earth abundant first row metals. We have synthesized novel CNC pincer ligands using NHC and pyridine donor groups for coordination to Co(I) and Ni(II) metal centers. The Ni(II) complexes are noteworthy for self-sensitized CO2 reduction to produce formate and CO. A record setting and long-lived metal centered excited state (ACS Catalysis, 2024) was believed to contribute to the promising catalytic properties. Further directions are being explored including the use of Co(I) complexes for CO2 hydrogenation reactions. An ultimate goal of this work is the formation of methanol and other high value products from CO2 hydrogenation or reduction. Several synthetic modifications to the metal complexes have been studied including 1) affixing electron donor or withdrawing groups to the pincer and 2) modification of the wingtip groups.