Synthesis, structural characterization, electrochemistry and spectroelectrochemistry of dinuclear copper(II) metal complexes stabilized by a tetradentate NOOO salicylaldimine ligands

The synthesis, structure, spectroscopic and electro-spectrochemical properties of salicylaldimine Schiff-base ligands (LnH) (n = 1, 2, and 3) (L1H = N-[2-amino-8-hydroxyquinoline]-salicylaldimine, L2H = N-[2-amino-8-hydroxyquinoline]-5-bromosalicylaldimine and L3H = N-[2-amino-8-hydroxyquinoline]-5-methoxysalicylaldimine), respectively, and their dinuclear copper(II) complexes [Cu2(Ln)2] are described. Three new dissymmetric tetradentate salicylaldimine ligands containing a donor set of NOOO were prepared by reaction of 2-amino-8-hydroxyquinoline with different salicylaldehydes. The dinuclear copper(II) metal complexes of these ligands were synthesized by treating an ethanolic solution of the appropriate ligand with an equimolar amount of Cu(Ac)2·H2O. The ligands and their copper complexes were characterized by FT-IR, UV–vis, 1H NMR, elemental analysis, molar conductivity, mass spectra and thermal analysis methods in addition to magnetic susceptibility and spectroelectrochemical techniques. The reaction of these ligands in a 1:1 mole ratio with copper(II) acetate afforded dinuclear Cu(II) metal complexes. The room temperature magnetic moments of [Cu2(Ln)2] complexes are found between 1.12 and 1.28 BM for per Cu(II) molecule.