Fig. 4: Effect of side group substitutions on CHO-CO coupling.

a Structural formulas of NHC molecules with side groups studied. b The dependence between ΔG of CHO-CO coupling and the Bader charge of carbene C atom. c The dependence between adsorption energies of CO (E_ads) and the Bader charge of carbene C atom. d A scaling relation between ΔG and E_ads.