SYNTHESIS, CHARACTERIZATION, AND ANTIOXIDANT ACTIVITY ON METAL(II) COMPLEXES OF A SCHIFF BASE DERIVED FROM THIOSEMICARBAZIDES AND O-VANILLIN

Abstract

A Schiff base derived from o-vanillin and thiosemicarbazide was synthesized, as well as its Mn(II), Fe(II), and Co(II) complexes. The Schiff base and its metal(II) complexes were characterized based on FTIR, solubility, melting/decomposition temperature, conductivity, and elemental analysis. From the analysis, the Schiff base was confirmed through the C=N IR peak (1648 cm^-1), and from the elemental analysis, the Schiff base to metal ratio of 1:2 was established. Molar conductivity measurement shows that all the complexes were in a range (18.0–47.0) hence they are non-electrolytic or non-ionic. Based on magnetic susceptibility measurement, the study further proposed the structure of the metal complexes to be octahedral in geometry and revealed that all the complexes were paramagnetic. Antioxidant activity of the synthesized compounds was analyzed with the DPPH free-radical–trapping process. The synthesized compounds exhibited lower antioxidant activity than the standard ascorbic acid. IC₅₀ values of the synthesized molecules measured from 20.226 to 59.454. All the synthesized compounds showed moderate antioxidant activity.