Preparation, spectral characterization and antimicrobial activities of Schiff base complexes derived from 4-aminoantipyrine. Mixed ligand complexes with 2-aminopyridine, 8-hydroxyquinoline and oxalic acid and their pyrolytical products

摘要

A series of biologically active mononuclear complexes of Cu(II), Ni(II), Zn(II), and Fe(III) were prepared. The reactions of the Schiff base ligand 1-phenyl-2,3-dimethyl-4-salicylalidene pyrazole-5-one, (HL), with the previous metals in the presence of LiOH as a deprotonating agent, yielded different types of complexes. The binary complexes react with the mixed ligands 2-aminopyridine (2-ampy), 8-hydroxyquinoline (8-OHqu) and Oxalic acid (Ox) to form the mixed ligand complexes. All the binary and mixed ligand complexes have octahedral configurations. The Schiff base ligand (HL) is coordinated to the central metal as monoanionic terdentate ONO ligand. Thermal studies explored the possibility of obtaining new complexes, which can not be prepared from solutions. Five coordinate Ni(II) and Zn(II) complexes were prepared pyrolytically. Also, the binuclear Fe(III) complex was prepared through the thermal transformation of its mononuclear complex to the binuclear one. All complexes and the corresponding thermal products were isolated and their structures were elucidated by elemental analyses, conductance, IR and electronic absorption spectra, magnetic moments, H-1 NMR and TG-DSC measurements. The free ligand (HL) and its metal complexes showed higher antibacterial effects than that of some investigated antibiotics.