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NNS tridentate thiosemicarbazide complexes of Zn(II) and Mn(II), 1,3,4-thiadiazole complex of Cd(II) and Hg(II) catalysed conversion of thiosemicarbazide into 1,3,4-oxadiazole: Synthesis, spectral and X-ray characterization


A. Bharti, A. Singh, A.K. Srivastava, N. K. Singh


Department of Chemistry, Banaras Hindu University, Varanasi- 221005, India

Email: singhnk_bhu@yahoo.co.in



The reactions of Zinc(II) and Mn(II) acetate with 1-picolinoyl-4-phenyl thiosemicarbazide (Hppts) yielded [Zn(ppts)2].CHCl3 (1) and [Mn(ppts)2].THF (2) but the reaction of Hppts with HgCl2 gave a cyclized product N-phenyl-5-(pyridin-2-yl)-1,3,4-oxadiazole-2-amine (Hppoa) (3). The treatment of thiosemicarbazide with conc. H2SO4 formed N-phenyl-5-(pyridin-2-yl)-1,3,4-thiadiazole-2-amine (Hppt) (4). It was observed that the thiosemicarbazide (Hppts) is a non-fluorescent material but its catalysed products 1,3,4-oxadiazole/1,3,4-thiadiazole are fluorescent materials with maximum emissions at 452/473 nm at an excitation wavelength at 252/259 nm. The reaction of cyclized ligand Hppt with Cd(OAc).2H2O gave [Cd2(ppt)2(-OAc)4] (5) which has a binuclear acetato-bridged seven coordinate pentagonal bipyarmidal geometry. In the solid state, the crystal structure of the ligand and complexes are stabilized by various types of hydrogen bonding forming supramolecular framework.


Keywords: Hppts, thiosemicarbazide, Ortep diagram



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