Preparation and Characterization of Novel Asymmetrical Schiff-Base Ligands Derived from 2-methyl-7-formyl-8-hydroxyquinoline and their Metal Complexes

Abstract

Two novel asymmetrical Schiff-base ligands, H2L1 and H2L2, were prepared by reacting two half-unit Schiff-base compounds with 2-methyl-7-formyl-8-hydroxyquinoline. The two half-unit Schiff-base compounds were initially prepared by condensing dimedone with either ethylenediamine or p-phenylenediamine, respectively. Both ligands are dibasic and contain two sets of NO coordinating sites. Twelve metal complexes were obtained by reacting both ligands with Cu(II), Ni(II), Co(II), Mn(II), Fe(III), VO(IV) cations. The ligands and their metal complexes were characterized by elemental analysis, IR, UV-Vis, ESR and mass spectra, also magnetic moments of the complexes were determined. Visible spectra of the complexes indicated distorted octahedral geometries around the metal cations. ESR spectra indicated mononuclear and dinuclear structures of the complexes of ligands H2L1 and H2L2, respectively. Magnetic moments of the complexes were rather low compared with those expected for octahedral geometries and indicated polymeric linkage of the metal complex molecules within their crystal lattices. The insolubility of the metal complexes in most organic solvents support the polymeric structures.