The Effect of N-Donor Ligands on Activation of [Ru(tpy)(L–py)(AcCN)] ²⁺ Precatalysts in CO ₂ Reduction Reaction Electrocatalysis

High Resolution Image Download MS PowerPoint Slide The electrocatalytic reduction of CO 2 to CO in anhydrous media requires the formation of the M–CO 2 bond. Using [Ru(tpy)(bpy)S] 2+ as a model, and substituting a pyridine of bipyridine( bpy ) for L = 123-triazole( 123-trz ), oxazole( oz ), pyrrole( pyrr ), pyrazole( pr z ), or NHC was computationally studied using TPPSh/def2-svp for geometries, SP correction with def2-tzvp, and implicit acetonitrile solvation. Complexes with pyrr, prz, and NHC undergo both reductions on the tpy ligand, shifting the second reduction to more negative potentials compared to bpy, 123-trz, and oz (which are at least 0.15 V more positive). For the latter, the second reduction occurs on the bidentate ligand generating [Ru(tpy · )(py-L · )AcCN] 0 . The general reaction path features two reductions, solvent dissociation to a pentacoordinated complex, and CO 2 association, except for NHC, where theoretical and experimental data suggest dissociation after the first reduction. Dissociation barriers varied from 19.0 ( oz ) to 12.9 kcal/mol ( prz ), while association barriers ranged from 9.0 ( NHC ) to 3.8 kcal/mol ( oz ). Finally, the cis / trans product ratio from CO 2 association is directly influenced by the τ 5 distortion parameter, serving as a qualitative indicator of selectivity.