Novel asymmetric tetradentate Schiff base ligands derived from 6-methyl-3-formyl-4-hydroxy-2-(1H)-quinolone and their metal complexes

摘要

Novel asymmetric, tetradentate, dibasic Schiff baseligands were synthesized by the condensation of the half-unitSchiff base ligand 3-[o-aminophenliminomethyl]-4-hydroxy-6-methyl-2-(1H)-quinolone with acetylacetone and salicylaldehyde.Cu(II), Ni(II), UO2(VI) and Fe(III) complexes of both ligands wereprepared using different salts in the case of Cu(II) and Ni(II)cations. The structures of the ligands and the complexes wereelucidated by chemical analyses, IR, UV-visible, mass spectra andmagnetic moment measurements. Both Cu(II) and Ni(II) cationsare initially coordinated to the N2O2 coordinating sites of theligands. The Cu(II) complexes were either square-planarmononuclear compounds, [LCu].xH2O, or dinuclear compounds,[LCu2(OAc)2], where both square-planar and octahedralgeometries exist in the same complex molecule, while the Ni(II)complexes were either diamagnetic square-planar orparamagnetic compounds where both octahedral and square-planargeometries do exist, indicating their anomalous behaviour. BothUO2(VI) and Fe(III) cations are initially coordinated to the outerO-O atoms of the ligand molecule(s). The uranyl complex of theligand H2La is coordinated to two ligand molecules while that ofligand H2Lb is coordinated to only one ligand molecule and to abidentate acetate group. The Fe(III) complexes are dinuclear whereeach Fe(III) cations are bridged through two chlorine atoms. Thegeometry of the uranyl complexes are pentagonal bipyramidalwhile the Fe(III) complexes are octahedral.