摘要:
Two novel symmetrical Schiff base ligands, H2L1 and H2L2 with tetradentate N2O2 and pentadentate N3O2 coordinating sites were prepared by the reaction of the aldehyde 2-methyl-7-formyl-8-hydroxy-quinoline with 1,3-diaminopropane or diethylenetriamine, respectively, in the molar ratio 2: 1. Cu(II), Ni(II), Co(II), Mn(II), Fe(III) and VO(IV) complexes of both ligands were synthesized. The ligands and their metal complexes were characterized by elemental analyses, IR, UV-Vis, ESR, NMR and mass spectra and also by magnetic moment measurements. Both ligands behave as tetradentate ones when coordinating metal cations. The ligand H2L1 has a smaller cavity than the ligand H2L2, thus the former ligand yielded mononuclear products, through chelation of one ligand molecule to a metal cation, while the latter ligand yielded binuclear products, through the coordination of two metal cations to two ligand molecules. Each of the Fc(III) cations was coordinated to three halves of both ligand molecules yielding also a mononuclear product with ligand H2L1 and a binuclear product with ligand H2L2. Either mononuclear or binuclear complex molecules link together forming polymeric chains. The mononuclear and binuclear complex forms were well manifested in the ESR spectra of the vanadyl complexes. The polymeric structures of the metal complexes led to an enhanced decrease of their magnetic moments through antiferromagnetic exchange between neighbouring metal cations.