1Department of Pure and Applied Chemistry, University of Calabar, Nigeria
Online published on 7 May, 2019.
The ligand, isonicotinylhydrazone-4-hydroxy-3-methoxybenzaldehyde (ISVN) was synthesized by the condensation reaction between isonicotinylhydrazide and 4-hydroxy-3-methoxybenzaldehyde (vanillin) at room temperature. The synthesized ligand was used to prepare the mixed ligand complexes of Co(II) and Zn(II) with aniline, furan and thiophene as secondary ligands. These complexes were characterized by using conductometry, elemental analysis, infrared and UV spectroscopic analysis. The melting points of the synthesized compounds were high (221.4 - 238.4°C) while the conductivities were low (0.09 - 1.19 μs). The infrared spectral data available proved that the ligand, ISVN coordinated to the metal ions through its nitrogen atom of the azomethine group and the phenolic oxygen atom of the vanillin ring thus illustrating the bidentate nature. The secondary ligands; aniline, furan and thiophene coordinated to the metal ions through their donor atoms viz nitrogen, oxygen and sulphur respectively. The electronic absorption bands depicted 4TIg →4A2g and 4TIg → 4T2g transitions for the Co(II) complexes revealing an octahedral geometry for the molecule while Zn(II) ion with no d-d transition show a band indicating charge transfer at 24,330cm-1 which is typical of tetrahedral geometry. The antimicrobial analysis was carried out using disc diffusion method on strains of Escherichia coli, Staphylococcus aureus and Salmonella typhi—the bacteria. The zones of inhibition (24.0–38.0mm and 23.0–34.0 mm)) caused by the cobalt and zinc complexes were significantly higher than that caused by streptomycin (24.0–26.0 mm) while the zones of inhibition on fungi i.e Candida albican, Trichophyton rubrum and Aspergillus niger caused by the same complexes were comparable with those caused by fluconazole. The minimum inhibitory concentrations (MICs) obtained for the ligand and the complexes were in the range of 2.5–10 mg/ml. The analysis proved that the synthesized compounds were bactericidal and fungicidal within the range of 2.5- 10 mg/ml
Synthesis, characterization, antimicrobial, ligand, complex
