Tracking Charge Accumulation in a Functional Triazole‐Linked Ruthenium‐Rhenium Dyad Towards Photocatalytic Carbon Dioxide Reduction
Philipp Gotico, Mai T.T. Tran, Aurélie Baron, Boris Vauzeilles, Christophe Lefumeux, Minh‐Huong Ha‐Thi, Thomas Pino, Zakaria Halime, Annamaria Quaranta, Winfried Leibl, Ally Aukauloo
Abstract
Abstract The [Re(bpy)(CO) 3 Cl] catalyst pioneered by Lehn for the two‐electron reduction of CO 2 has constantly revealed unique facets in the mechanistic understanding of the selective transformation of CO 2 . A novel triazole‐linked ruthenium photosensitizer and a rhenium catalyst dyad was synthesized and investigated for photo‐induced charge accumulation using time‐resolved absorption spectroscopy. The triazole bridging ligand promoted weak electronic communication between the two units, resulting in an anodic shift of the reduction potentials of the Re moiety. Upon excitation of the photosensitizer, the first reduction of the catalyst occurred with a fast apparent rate of >5×10 7 s −1 . Using a double‐excitation nanosecond pump‐pump‐probe setup to track the second electron accumulation on the catalytic unit was not conclusive as no observable absorption changes occurred upon the second excitation, suggesting a pathway for an efficient intramolecular reverse electron transfer preventing the two‐electron accumulation at the catalyst under our experimental conditions. Nevertheless, under continuous irradiation and with the use of sacrificial electron donors, photocatalytic CO 2 reduction assays showed good turnover numbers, hinting at the non‐innocent role of byproducts in solution.