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 ReI 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.