Copper(II) complexes of 13-membered amide-based macrocyclic ligands: Effect of electronic substituents on redox properties

1369-1379The present work discusses copper(II) complexes of 13–membered macrocyclic ligands carrying electronic substituents on the ligand periphery. The complexes have been thoroughly characterized including crystallographic investigations of two representative compounds. The crystal structures confirm that the metal center is coordinated by two deprotonated Namide and two neutral Namine atoms in an N4 basal plane within the macrocyclic cavity. The electrochemical studies suggest that the different electronic substituents present on the ligand periphery (–H, –Cl, –CH3, and –OCH3) significantly alter the CuIII–CuII potential values. Based on the electrochemical findings, the transient Cu(III) species generated coulometrically are characterized by their absorption spectra