Synthesis, Characterization, Antioxidant and Antibacterial Activities of Thiosemicarbazide Derived Schiff Base and its Metal Complexes

Law, Shiaw Yee (2020) Synthesis, Characterization, Antioxidant and Antibacterial Activities of Thiosemicarbazide Derived Schiff Base and its Metal Complexes. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Synthesis of novel thiosemicarbazide derived Schiff base by the condensation reaction of 4-methyl-3-thiosemicarbazide (MT) and 4-(p-acetoxyphenyl)-2-butanone (4ACT) was successfully carried out. The synthesized Schiff base (MT4ACT) was reacted with transition metal acetate salt of Cd(II), Cu(II), Ni(II) and Zn(II) respectively yielding metal complexes with stoichiometry molar ratio of 1:2 (metal: ligand) with a general formula of M(MT4ACT)2 where M = Cd, Cu, Ni and Zn. These compounds were characterized by different analytical techniques, such as FTIR-ATR, UV-Vis, 1H NMR, 13C NMR and molar conductivity. The results showed that Schiff base behaved as a bidendate NS donor ligands and coordinated via azomethine nitrogen and thiolate sulphur. The proposed geometries of the 1:2 metal complexes were square planar or tetrahedral. The FTIR spectrum confirmed that the ligand existed in thione form in solid state. Furthermore, the NMR spectrum confirmed that the ligand existed in thione form in solution state. The stoichiometry concluded from the analytical data was in good agreement with the proposed formula of the ligand and metal complexes. The Schiff base and its metal complexes were evaluated for their in vitro antioxidant activity at the concentrations range from 62.5 to 2000ppm via 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The results revealed that only Schiff base showed antioxidant activity with an IC50 value of 275.4ppm. Moreover, in vitro antibacterial activities of Schiff base and its metal complexes were also tested against one Gram-positive bacterium, namely, Staphylococcus aureus and one Gram-negative bacterium, namely, Escherichia coli. All Schiff base and metal complexes were found to be inactive and unable to inhibit the growth of S. aureus and E. coli.