Schiff base derived from 2-aminophenol and 3-formyl-2-hydroxy-6-methoxyquinoline and its Mn(II) and Fe(II) complexes were synthesized and characterized by melting point and decomposition temperature, elemental analysis, molar conductivity, infrared (IR) spectral analysis, atomic absorption spectroscopy (AAS) analysis, solubility test, and magnetic susceptibility. The Fourier-transform infrared spectroscopy (FTIR) spectral data of the Schiff base determined showed a band at 1622 cm −1 and this was assigned to the v (C=N), which is a feature of azomethine group. The same band was observed to shift to lower frequencies 1577 and 1599 cm −1 in the complexes suggesting coordination of the Schiff base with the respective metal(II) ions. Molar conductance values 14.58 and 12.65 Ω −1 •cm 2 •mol −1 show that the metal complexes were non-electrolyte in nature. The magnetic susceptibility of the complexes was determined and the gram magnetic susceptibility of the complexes was found to be positive, revealing that they are paramagnetic. The elemental analysis of the complexes for C, N and H determined suggested 1:1 metal to ligand ratio. The result of the antimicrobial studies showed that, the metal(II) complexes exhibited better antibacterial and antifungal activity than the Schiff base.

Schiff base derived from 2-aminophenol and 2-hydroxy-6-methoxy-3-quinolinecarboxaldehyde and its Co(II) and Ni(II) complexes were synthesized and characterized by elemental analysis, melting point and decomposition temperature, molar conductivity, IR spectral analysis, AAS analysis, solubility test, and magnetic susceptibility. The FTIR spectral data of the Schiff base determined showed a band at 1622cm-1  which was assigned to the v(C=N), a feature of azomethine group. The same band was observed to shift to lower frequencies 1577 and 1599cm-1 in the complexes suggesting coordination of the Schiff base with the respective metal (II) ions. Molar conductance values 14.58 and 12.65Ω-1cm2mol-1show that the metal complexes were non-electrolytic in nature. The magnetic susceptibility of the complexes were determined and the gram magnetic susceptibility of the complexes were found to be positive, revealing that they are paramagnetic. The elemental analysis of the complexes for C, N and H determined suggested (1:1) metal to ligand ratio.  The result of the antimicrobial studiesthat, the metal (II) complexes exhibited higher antibacterial and antifungal activity than the Schiff base but lower than the reference drugs Amoxicillin and Ketoconazole used as control in all cases.   

Schiff base of 4-methyl-o-phenylenediamine and 2-hyroxy-1-napthaldehyde was synthesized and was used to prepare some metal (II) complex by refluxing with Metal (II) chloride ions. The ligand and its complexes were characterized by melting point and decomposition temperature, FTIR, solubility, magnetic susceptibility, conductivity measurement and elemental analysis. The IR spectral data revealed that, the  Schiff base coordinated to the respective metal(II) ion through the azomethine nitrogen and phenolic oxygen due to the shifting  of the azomethine band υ(C = N) from 591cm–1 to 1603 and 1581cm-1 in the spectra of the complexes. The band at 567 and 563cm-1 were due to υ(M–N), and 729-752cm–1 due to υ(M–O) and the infrared spectra of the metal(II) complexes showed strong bands 3443 and 3363cm–1 suggesting the presence of coordinated water in the metal complexes. Molar conductance values determined 9.17 and 10.04W–1cm2mol–1 showed that, the complexes were non-electrolytes. The ligand and its metal (II) complexes are not soluble in water and most organic solvents except DMF and DMSO. The melting point of the ligand and the decomposition temperatures of the metal (II) complexes were 243 and 224oC, which indicated their good thermal stability. The magnetic moment values of the metal (II) complexes obtained were 5.65 and 5.22BM for Mn(II) and Fe(II) complexes. This positive values indicated that they were paramagnetic. The elemental analysis suggested a metal to ligand ratio of 1:2. The antibacterial and antifungal test carried out on the ligand and its metal(II) complexes sowed moderate activity.