Supramolecular Assembly Promotes the Electrocatalytic Reduction of Carbon Dioxide by Re(I) Bipyridine Catalysts at a Lower Overpotential

The addition of methyl acetamidomethyl groups at the 4,4'-positions of a 2,2'-bipyridyl ligand is found to enhance the rate of a bimolecular reduction mechanism of CO2 by Re(II)fac-tricarbonyl chloride complexes. Electrochemical studies, spectroelectrochemical measurements, and molecular dynamics simulations indicate that these methyl acetamidomethyl groups promote the formation of a hydrogen-bonded dimer. This supramolecular complex catalyzes the reductive disproportionation of CO2 to CO and CO32- at a lower overpotential (ca. 250 mV) than the corresponding single-site 2 e- reduction of CO2 to CO and H2O catalyzed by the corresponding model complex with a 4,4'-dimethyl-2,2'-bipyridyl ligand. These findings demonstrate that noncovalent self-assembly can modulate the catalytic properties of metal complexes by favoring alternate catalytic pathways.