CO²⁺, NI²⁺, CU²⁺, ZN²⁺ AND VO²⁺ COMPLEXES DERIVED FROM 5-PHENYL-1,3,4-OXADIAZOLE-2(3H)-THIONE

In this study, five novel coordination compounds of 5-phenyl-1,3,4-oxadiazole-2(3H)-thione (FODT) with Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, and VO²⁺ ions were successfully synthesized and comprehensively investigated. The ligand was prepared via a condensation reaction between benzoyl hydrazide and potassium isothiocyanate. The metal complexes were obtained in solution using a 1:2 metal-to-ligand molar ratio. The synthesized compounds were characterized by IR spectroscopy and X-ray structural analysis. IR spectral data confirmed that the ligand coordinates to the metal ions through nitrogen and sulfur donor atoms, forming N,S-chelate complexes. X-ray crystallographic analysis revealed that the Cu(II) complex adopts a square-pyramidal geometry. Based on spectral and analytical data, octahedral geometries were proposed for the Co(II) and Ni(II) complexes, while the Zn(II) complex was suggested to possess a tetrahedral coordination environment. The antimicrobial activity of all synthesized compounds was evaluated using the disk diffusion method against Staphylococcus aureus, Escherichia coli, and Candida albicans test strains. All metal complexes exhibited significantly higher biological activity compared to the free ligand. Among them, the Cu(II) and VO²⁺ complexes demonstrated the strongest antimicrobial effects. These findings indicate that FODT-based metal complexes may be considered promising candidates for the development of new biologically active compounds.