Structural effect of imidazolium salts on electrochemical conversion of carbon dioxide to imidazolium carboxylate

Imidazolium salts with various alkyl side chains and counter anions were synthesized. The conversion of CO₂ to N-heterocyclic carbene-CO₂ adducts (NHC-CO₂) were achieved by in situ electroreduction of the imidazolium salts under CO₂ atmosphere. The yield of NHC-CO₂ decreases with the increase of steric effect of alkyl side chains, which is attributed to the decrease of reactivity of NHCs in the case of strong steric effect. The hydrogen bond accepting ability of anion has a substantial effect on the conversion of CO₂. The high ability of anion to establish hydrogen bond favors the conversion of CO₂. A good correlation between hydrogen bond accepting abilities of anions and yields of NHC-CO₂ was demonstrated.