Calix[8]arene-based Ni(II) complexes for electrocatalytic CO2 reduction

The electrochemical behavior and catalytic activity for the electroreduction of CO2 of complexes of Ni-(II) containing phenanthroline-based ligands, with or without a calixarene scaffold, were tested. The complexes were characterized by spectroscopic techniques, and their electrocatalytic properties determined by cyclic voltammetry. With water as proton source the complex [(1,5-(2,9-dimethyl-1,10-phenanthro)-p-tert-butylcalix[8]arene) NiCl2] (1) presented a significant increase in current at E = -2.36 V (relative to Ag/AgCl reference electrode) when reduced under an atmosphere of CO2, indicating that an electrocatalytic process occurs. Thus, calix[8] arenes that feature a phenanthroyl moiety as bidentate N-ligands, and an intramolecular proton source in the phenolic -OH groups, afford Ni-(II) electrocatalysts for the reduction of CO2.