Synthesis, Characterization, and Biological Activity of Transition Metal Complexes of Oxadiazole

A new oxadiazole and its metal complexes have been synthesized and characterized. The ligand potassium 2-(2-phenylisonicotinoyl)hydrazinecarbodithioate [K+(H2L)-] (1) on reaction with transition metals in EtOH-H2O medium undergoes cyclization and converted to 5-(2-phenyl-4-pyridyl)-1,3,4-oxadiazole-2-thione (ppot), which yielded a series of mononuclear transition metal complexes. Four transition metal complexes of ligand are prepared and characterized based on elemental analysis, IR,1H NMR, UV-vis spectra, and thermogravimetry-differential thermal analysis (TG-DTA). From the obtained data, the structure of complexes has the general formula [M(ppot)2Cl2(H2O)2], where M [image omitted] Cu(II), Co(II), Ni(II), Zn(II). The thermal behaviors of these complexes showed that the complexes lost coordinated water molecules in the first step followed by decomposition of the ligand molecule in the subsequent steps. The ligand and its transition metal complexes were screened against fungi and bacteria in vitro. Data obtained showed that the ligand itself showed moderate biological activity, whereas the metal complexes exhibited a higher inhibition towards both bacteria and fungi.