Synthesis, Characterization, and Antioxidant Activities of Schiff Base and Fe(II) Complex

Abstract

A new Schiff base (HL) ligand has been synthesized by condensing of ethyl 2-amino-5,5,7,7- tetramethyl-4,5,6,7-tetrahydrothieno[2,3-c]pyridine-3-carboxylate and 2-hydroxybenzaldyde. In turn, its Fe(II) complex was prepared, having the following general formula: [LFeCl(H2O)2]∙H2O. The geometry of the Fe(II) complex has been revealed by a variety of characterization techniques. Synthesized Schiff base and its Fe(II) complex were also characterized by numerous analytical methods including NMR, FTIR, UV-visible, mass spectrometry, thermogravimetric–differential thermal analysis (TGA–DTA), elemental analysis, molar conductivity, and magnetic susceptibility for structural elucidation. Results showed that Fe(II) complex decompose in two consecutive stages. The Fe(II) complex was found to have an octahedral geometry. The results show that the Fe ion is coordinated to the Schiff base ligand by carbonyl oxygen, azomethine nitrogen and phenolic oxygen atoms. Schiff base ligand and its Fe(II) complex were also subjected to antioxidant activity studies using in vitro DPPH and ABTS assays. The Fe(II) complex exhibit high in vitro antioxidant activities in both DPPH and ABTS assays. The IC50 values of the complex was found to be 18,34 μg/mL and 35,0 μg/mL, respectively. However, the ligand did not show any antioxidant effects in both methods. These results showed that Fe(II) has effective antioxidant ability compare to the standards.