The Role of Redox Potential and Molecular Structure of Co(II)-Polypyridine Complexes on the Molecular Catalysis of CO2 Reduction

In this work, we report the electrochemical response of a family Co(II) complexes, [CoII(L)3]2+ and [CoII(L’)2]2+ (L = 2,2’-bipyridine, 1,10-phenanthroline, 3,4,7,8-tetramethyl-1,10-phenanthroline, 5,6-dimethyl-1,10-phenanthroline, 4,7-diphenyl-1,10-phenanthroline; L’ terpyridine 4-chloro-terpyridine), in presence absence CO2 order to understand role redox potential molecular structure on catalysis reduction. The tris chelate complexes exhibited three electron transfer processes ⇄ [CoIII(L)3]3+ + 1e−, [CoΙΙ(L)3]2++1e− [CoΙ(L)3]+, [CoΙ(L)3]+ 2e- [CoΙ(L)(L−)2]−. case with 1,10-phen 2,2-bipy, third process showed coupled chemical reaction [CoΙ(L)(L−)2]− → [CoΙ(L−)2]− L. For bis associated couples [CoΙΙ(L)2]/[CoIII(L)2]3+, [CoΙΙ(L)2]2+/[CoΙ(L)2]+, [CoΙ(L)2]+/[CoΙ(L)(L−)] were registered, including only for complex containing ligand 4-chloro-terpyridine. Foot wave analysis (FOWA) obtained from cyclic voltammetry experiments allowed us calculate catalytic rate constant (k) [Co(3,4,7,8-tm-1,10-phen)3]2+ presented high k value; moreover, [Co(4-Cl-terpy)3]2+ did not show activity, indicating that more negative increased catalysis. Density functional theory (DFT) calculations compounds rationalize effect electronic