Studies on carbon dioxide binding to metal macrocycles using electrochemical technique

Nickel azamacrocycles act as efficient electrocatalysts for the reduction of carbon dioxide in terms of reduction potential, stability and catalytic current, The extent of catalytic activity is dictated by the size of macrocy clic ring, extent and saturation in the ring of substituents on the ring. Studies of carbon dioxide binding to the nickel complexes allow one to choose an appropriate catalyst among the preferred ones. With this aim. the binding constants for various CO2 -nickel azamacrocycles were determined by electro cyclic voltammetry in acetonitrile, These values exhibit a strong correlation with the Ni(II)/Ni (I) redox potential and a weak correlation with the solvent dielectric constant, when studies were carried out in the presence of various solvents, The Kco2 of square planar complexes seem to be influenced by the bond strength of Ni - CO2 solvation effect and geometric structure around the metal complex upon carbon dioxide binding. The results will be discussed in the light of comprehensive data.