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

Chong, Jing Man (2019) Synthesis, Characterization, and Antioxidant Activities of Thiosemicarbazide Derived Schiff Base and the Metal Complexes. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

The aim of this project was to synthesize and characterize a novel thiosemicarbazide derived Schiff base with its Copper(II) (Cu) and Cadmium(II) (Cd) complexes. Antioxidant activities of the synthesized Schiff base and its metal complexes were studied via DPPH free radical scavenging method. In this study, a thiosemicarbazide derived Schiff base (E)-N-phenyl-2-((E)-3- phenylallylidene)hydrazine-1-carbothioamide (PTCA) was synthesized from transcinnamaldehyde and 4-phenyl-3-thiosemicarbazide by conventional condensation reaction. The compound was characterized by FTIR-ATR, DSC, 1H and 13C NMR, and UV-Vis analyses. Cu(II) and Cd(II) complexes of PTCA were synthesized and characterized by FTIR-ATR, DSC, UV-Vis, FAAS, and magnetic susceptibility analyses. FTIR-ATR confirmed that PTCA coordinates to the respective metal ions via the thiolate sulphur atom. Analytical data from FAAS confirmed that the complexes have metal to ligand stoichiometry of 1:2. Cu(PTCA)2 is a paramagnetic compound which contains one unpaired electron. The antioxidant studies of synthesized compounds were measured by half maximal inhibitory concentration value (IC50). Lower IC50 value corresponds to higher antioxidant activity. Results show that the metal complexes exhibit higher antioxidant activities than free Schiff base ligand. IC50 values of the compounds are; PTCA: IC50 = 112.7 ppm, Cu(PTCA)2: IC50 = 9.413 ppm, and Cd(PTCA)2: IC50 = 56.63 ppm. The order of free radical scavenging activity of the compounds is Cu(PTCA)2 > Cd(PTCA)2 > PTCA. Cu(PTCA)2 was the most active among the synthesized compounds with IC50 value of 9.413 ppm.