Synthesis and characterization of copper(II) complexes with dissymmetric tetradentate Schiff base ligands derived from aminothioether pyridine.: Crystal structures of [Cu(pytIsal)]ClO4•0.5CH3OH and [Cu(pytAzosal)]ClO4

Five dissymmetric tetradentate Schiff base ligands, containing a mixed donor set of NSNO were prepared by the reaction of aminothioether pyridine with the appropriate salicylaldchyde and characterized by FTIR, H-1 and C-13 NMR and elemental analysis methods. The complexes of these ligands were synthesized by treating an ethanolic solution of the appropriate ligand with an equimolar amount of Cu(ClO4)(2).6H(2)O and methanolic NaOH or alternatively by a more direct route in which the two reactants are added to a solution of the ligand immediately after formation of the ligand and prior to any isolation. The copper(II) complexes, [Cu(pytXsal)]ClO4 (4-X-2-{[2-(2-pyridin-2-yl-ethylsulfanyl)ethyliminolmethyl) phenol copper(11)) (X iodo (1), bromo (Br), nitro (NO2), methoxy (OMe), phenylazo (Azo)) were characterized by FTIR, elemental analysis, electronic spectra and molar conductivity. The ligand functions as a monobasic tetradentate ligand bonding through the thiolate sulfur, azomethine and pyridine nitrogens and phenolate oxygen. All of the complexes were found to be 1:1 electrolyte systems in acetonitrile. Electronic spectra show that the copper complexes have a tetrahedrally distorted square planar environment. The single crystal X-ray diffraction is reported for [Cu(pytlsal)]ClO4.0.5CH(3)OH (A) and [Cu(pytAzosal)]ClO4 (B). The copper atom in both complexes lies in a slightly tetrahedrally distorted square planar coordination. Cyclic voltammetry indicates that complexes of [Cu(pytXsal)]ClO4 (X = NO2, Azo) have a quasi-reversible redox behavior and complexes of [Cu(pytXsal)]ClO4 (X = I, OMe) undergo irreversible reduction under the experimental conditions. (C) 2003 Elsevier Science Ltd. All rights reserved.