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
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(µ-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
1. The Chemistry of Pincer Compounds, ed. D. Morales-Morales and M. C. Jensen, Elsevier, Amsterdam, The Netherlands, 2007.
2. (a) S. Datta, D. K. Seth, R. J. Butcher and S. Bhattacharya, Inorg. Chim. Acta, 2011, 377, 120; (b) P. Paul, S. Datta, S. Holder, R. Acharyya, F. Basauli, R. J. Buchter, S.-M. Peng, G.- H. Lee, A. Castiñeiras and Bhattacharya, J. Mol. Catal. A: Chem., 2011, 324, 62.