Spectroscopic studies of bimetallic complexes derived from tridentate or tetradentate Schiff bases of some di- and tri-valent transition metals

Abstract

Two series of new binuclear complexes with Schiff base ligands, H 4L a or H 2L b, derived from the reaction of 4,6-diacetylresorcinol and ethylenediamine, in the molar ratio 1:1 and 1:2 have been prepared, respectively. The two ligands react with Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Cr(III) and Fe(III)-nitrates to get binuclear complexes. The ligands were characterized by elemental analysis, IR, UV–vis, 1H NMR and mass spectra. The complexes were synthesized by direct and template methods. Different types of products were obtained for the same ligand and metal salts according to the method of preparation. The H 4L a ligand behaves as a macrocyclic tetrabasic with two N 2O 2 sits, while the H 2L b ligand behaves as a dibasic with two N 2O sites. The H 4L a ligand is a compartmental ligand which hosts the two metal ions at the centers of two cis-N 2O 2 sites, while the metal complexes of H 2L b ligand are binuclear, where the ligand hosts two metal ions at the centers of two N 2O sites. In both cases, deprotonation of the hydrogen atoms of the phenolic OH groups occur except in the case of the Ni(II), Fe(III) and Cr(III) complexes. Electronic spectra and magnetic moments of the complexes indicate that the geometries of the metal centers are either octahedral or tetrahedral. The structures are consistent with the IR, UV–vis, ESR, 1H NMR, mass spectra, and thermal gravimetric analysis (TGA/DTA) as well as conductivity and magnetic moment measurements.