Synthesis, Characterization and Antioxidant Studies of Thiosemicarbazide Derived Schiff Bases and its Metal Complex

Khor, Shu Hui (2020) Synthesis, Characterization and Antioxidant Studies of Thiosemicarbazide Derived Schiff Bases and its Metal Complex. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

A Schiff base (PTCA) of 4-phenyl-3-thiosemicarbazide with trans-cinnamaldehyde was synthesized via condensation reaction in the molar ratio 1:1. The synthesized Schiff base was purified by recrystallization in hot absolute ethanol. The synthesized ligand was used to prepare metal complexes of Cu(II), Ni(II) and Zn(II) and characterized by several analysis techniques. The novel compounds formed has been structurally characterised by Fourier-Transformed Infrared (FTIR), Ultraviolet-visible (UV-Vis) spectrophotometer, Flame Atomic absorption spectroscopy (FAAS), 1H and 13C Nuclear Magnetic Resonance (NMR) spectrometer, Differential Scanning Calorimetry (DSC). According to the analysis, it shows that the Schiff base existed as thione tautomer and a bidentate complex was formed as the Schiff base synthesized was coordinated to the metal ion through azomethine N and thione S. The characterization result of synthesized Schiff base was conforms to the corresponding proposed structure. All the synthesized compounds including Schiff base and its metal complexes were evaluated on its antioxidant activity. The study on the radical scavenging activity was carried out by using 1,1-diphenyl-2-picrylhydrazyl (DPPH) as substrate in order to obtain half maximal inhibition concentration value (IC50). The results of the DPPH antioxidant assay proved that the copper complex of (E)-N-phenyl-2-((E)-3-phenylallylidene) hydrazine-1-carbothiomide (PTCA) is the most potent antioxidant among all the metal complexes.