An electrochemical investigation of the structure of copper(II) complexes of Schiff base ligands derived from salicylaldehyde and substituted anilines

An electrochemical investigation has been carried out on a series of Schiff base copper(II) complexes derived from salicylaldehyde and substituted anilines in the attempt to correlate the solid-state geometry of the CuN 2O2 core, which is conditioned by the steric encumbrance of the different peripheral substituents, and the corresponding solution structures as inferred from either the distinctive features of the Cu(II)/Cu(I) reduction or the EPR characteristics of the original complexes. Even if a good agreement is expected between the extent of chemical reversibility of the reduction process and the tetrahedral distortion of the complexes, it has been found, that in reality, the chemical reversibility of the reduction process also holds for nominally planar complexes in that they are sufficient flexible to pass from planar to tetrahedral arrangements upon addition of one electron. The relative location of the Cu(II)/Cu(I) formal electrode potentials appears more pertinent in that the higher is the distortion the less negative is the potential value.