Novel Asymmetric Tetradentate Schiff Base Ligands Derived from 6-Metwia-Formyl4-Hydroxy-2-(1H)-Quinolone and Their Metal Complexes

Abstract

Novel asymmetric, tetradentate, dibasic Schiff base ligands were synthesized by the condensation of the half-unit Schiff base ligand 3-[o-aminophenyliminomethyl]-4-hydroxy-6-methyl-2-(1H)-quinolone with acetylacetone and salicylaldehyde. Cu(II), Ni(II), UO₂ (VI) and Fe(III) complexes of both ligands were prepared using different salts in the case of Cu(II) and Ni(II) cations The structures of the ligands and the complexes were elucidated by chemical analyses, IR, UV-visible, mass spectra and magnetic moment measurements. Both Cu(II) and Ni(II) cations are initially coordinated to the N₂O₂ coordinating sites of the ligands The Cu(II) complexes were either square-planar mononuclear compounds, [LCu]. xH₂O, or dinuclear compounds, [LCu₂(OAc)2], where both square-planar and octahedral geometries exist in the same complex molecule, while the Ni(II) complexes were either diamagnetic square-planar or paramagnetic compounds where both octahedral and square-planar geometries do exist, indicating their anomalous behaviour. Both UO₂(VI) and Fe(III) cations are initially coordinated to the outer O-O atoms of the ligand molecule(s) The uranyl complex of the ligand H₂L^a is coordinated to two ligand molecules while that of ligand H₂Lb is coordinated to only one ligand molecule and to a bidentate acetate group. TheFe(III) complexes are dinuclear where each Fe(III) cation is linked to orlly one ligand molecule and the two Fe(III) cations are bridged through two chlorine atoms. The geometry of the uranyl complexes are pentagonal bipyramidal while the Fe(III) complexes are octahedral.