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Title:	Synthesis, characterization and antimicrobial studies of organotin(iv) complexes of thiosemicarbazide and semicarbazide
Authors:	Nasry Jassim Hussien (P68268)
Supervisor:	Siti Fairus Mohd Yusoff, Assoc. Prof. Dr.
Keywords:	Organotin compounds Universiti Kebangsaan Malaysia -- Dissertations Dissertations, Academic -- Malaysia
Issue Date:	15-Jan-2019
Description:	The organotin (IV) complexes derived from semicarbazide/thiosemicarbazide and semicarbazone/thiosemicarbazone ligands represent an interesting class of organometallics compounds. These species have several potential applications including their role as antimicrobial agents. These types of ligands have the ability to stabilize a number of oxidation states and coordination geometries of the central ion. In the present work, a series of 28 semicarbazide/thiosemicarbazide ligands and 20 organotin (IV) complexes were synthesized and characterized. A range of physico-chemical techniques were used to confirm the entity of chemical structure of these species. These include CHNS microelemental analysis, FTIR, Nuclear Magnetic Resonance (NMR) spectroscopy and X-Ray crystallography techniques. All the newly synthesized derivatives were isolated in high yields. The melting points of the compounds lies in the range 190-334°C, bar from 11, 19 and 20. The FTIR spectra of the tin compounds exhibit several new stretching frequencies, compared with their free ligands, at 685-522, 468-429 and 360-329 cm-1 assigned to v(Sn-O), v(Sn-N) and v(Sn-S), respectively. These stretching frequencies confirm the complexation of dimethyltin (IV) to the ligands via oxygen, nitrogen and sulfur. The absence of v(NH) stretching frequencies of the newly synthesized complexes in the range 3371-3134 cm-1 is a strong indication of the involvement of thiolate sulfur and iminol oxygen in the coordination. The 1H-NMR spectra of synthesized derivatives revealed chemical shift in the range δ 5.1–9.9 ppm that correlated to the amino proton (NH). Further, the 13C-NMR spectra of the synthesized ligands show distinct C=S and C=O carbon shifts in the range δ 187.5-177.8 and 169.8-152.1 ppm, which shifted to δ 186.49-170.85 and 167.39-150.05 ppm, respectively upon complexation to the tin center. The chemical shift is an indication of the coordination between S/O with the tin atom. The 119Sn-NMR spectra of complexes displayed chemical shift in the range δ -250 to -103 ppm. The characterization data demonstrated the formation of tetra-, penta- and hexa-coordinate dimethyltin (IV) semicarbazone and thiosemicarbazone complexes with tetrahedral, distorted trigonal bipyramidal and distorted octahehedral arrangement about Sn atom, respectively. The X-ray single crystal structure of ligands exhibit distortion and no plane of symmetry could be observed. In the crystal structure of compounds 21, 22 and 23, the incorporation of the solvent molecule of the acetone resulted in the deviation of the molecular arrangement from the expected geometry. Antibacterial studies against six marine-pathogenic bacteria and eight human-pathogenic bacteria (both Gram positive and Gram negative) were performed using disc diffusion techniques. Ampiciline at the concentration of 10 mg/mL was used as a control. The results of the antimicrobial studies revealed the organotin (IV) complexes possessed enhanced inhibition activities, compared with their free ligands. Upon changing the reaction medium (solvent), several unexpected compounds were isolated during the course of this study. These compounds were characterized using a range of analytical and spectroscopic techniques including single crystal X-ray analysis.,Ph.D.
Pages:	327
Call Number:	QD412.S7H837 2019 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

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