Group 6 (Cr, Mo, W) and Group 7 (Mn, Re) bipyridyl tetracarbonyl complex for electrochemical CO₂ conversion: DFT and DLPNO-CCSD(T) study for effects of the central metal on redox potential, thermodynamics, and kinetics

To reveal the effects of central metal on the catalytic efficiency, we estimated the thermodynamics and kinetics of CO₂ reduction by Group 6 and Group 7 metal bpy tetracarbonyl complexes using DLPNO-CCSD(T) method. The applied potential V1 required for the formation of the two-electron reduced species of the metal bpy tetracarbonyl complex is greater than the applied potential V2 required for the formation of the two-electron reduced species of the metal bpy tricarbonyl complex, and for each applied potential, the effect of the central metal on the reaction process was investigated. At applied potential V1, CO₂ binding to metal center was the rate-limiting step in CO₂ reduction by the Group 6 complex, while the second proton transfer was the rate-limiting step for CO₂ reduction by the Group 7 complex. At applied potential V2, the rate-limiting step was the dissociation of the CO ligand from the central metal, except for Cr.