Influence of Intermolecular Hydrogen Bonding Interactions on the Electrocatalytic Reduction of CO2 to CO by 6,6′-Amine Substituted Rhenium Bipyridine Complexes

The introduction of biologically inspired motifs into electrocatalysts is an attractive strategy for efficiently transforming harmful fossil fuel combustion products such as carbon dioxide into useful chemical fuels. Herein, we present a series of Re(bpy)(CO)(3)Cl electrocatalysts with pendant primary, secondary, and tertiary amines with the aim of determining the effect of available pendant protons on the reduction of CO2 to CO. Cyclic voltammetry studies indicate that the availability of pendant protons leads to intermolecular hydrogen bonding interactions, altering the electrochemical behavior of the complexes. Further, controlled potential electrolysis studies show a clear trend in the catalytic activity of these complexes based on the availability of pendant protons. For the NMe2-substituted complex with no pendant protons, the Faradaic efficiency (FE) remains quite stable with changing potential (41-65 % FECO), but for the NH2-substituted complex with maximum available pendant protons, the FECO increases with more negative potentials, peaking at 83 % FECO. Together with the formation of H-2 by the NH2-substituted Re(bpy)(CO)(3)Cl complex, this suggests a change in electrocatalytic behavior due to the intermolecular hydrogen bonding interactions that occur with additional pendant protons.