Multi-properties of a new azo-Schiff base and its binuclear copper(II) chelate: Preparation, spectral characterization, electrochemical, potentiometric and modeling studies

Abstract

In this study, NN– chromophore group containing a new Schiff base ligand 2-{(E)-[(3-hydroxy-4-methoxyphenyl)imino]methyl}-4-[(E)-phenyldiazenyl]phenol H2L.3/2H2O, formed by the 1:1 M condensation of 5-amino-2-methoxyphenol with 2-hydroxy-5-[(E)-phenyldiazenyl]benzaldehyde and the binuclear copper(II) chelate of this ligand have been prepared. The structures of the ligand and its Cu(II) chelate have been elucidated on the basis of elemental analyses, conductivity measurements, spectral (FT-IR, 1H and 13C NMR and UV.–Vis.), electrochemical studies and theoretical calculations. Cu(II) ion coordinates with the ligand through the oxygen of the phenolic and nitrogen of azomethine group. The redox behaviors of the ligand and its binuclear Cu(II) chelate were investigated in DMSO solution containing 0.1 M tetrabutylammoniumtetrafluoroborate (TBATFB) as supporting electrolyte by cyclic voltammetry (CV). Five dissociation constants were determined for the prepared azo-Schiff base ligand as 3.25 (pKa1), 5.51 (pKa2), 7.18 (pKa3), 9.60 (pKa4) and 11.10 (pKa5). Also, the stability constants of the Cu(II) chelate have been calculated by SUPERQUAD computer program and general mechanisms have been proposed with regard to the formation of the complex.