Synthesis, Characterization, Antimicrobial activty and Antioxidant Activity of Some Metal Complexes with 4-((4-bromobenzylidene)amino)-5-(pyridin-4-yl)-4H-1,2,4-triazole-3-thiol

Abstract

The work describes the synthesis and spectral investigation of Co (II), Ni (II), Cu (II), and Zn (II) complexes with 4-((4-bromobenzylidene)amino)-5-(pyridin-4-yl)-4H-1,2,4-triazole-3-thiol (L). The new ligand was synthesized through three successive steps: first, the preparation of the potassium salt of isoniazid with an alkaline solution of carbon disulfide; second, the ring closure of the potassium salt with an excess of hydrazine hydrate; and finally, the last step involved the condensation of 4-amino-1,2,4-triazole with 4-bromobenzaldehyde in glacial acetic acid as a catalyst to afford a good yield of the new Schiff base, L. The physical and spectroscopic properties of the ligand and its complexes were well studied. The ligand L has been used to synthesize new complexes of Co (II), Ni (II), Cu (II), and Zn (II), which have been characterized by using different techniques, such as FT-IR, UV-Vis, 1H-NMR, and 13C-NMR spectrophotometric techniques, as well as elemental analysis C.H.N.S. and flam atomic absorption FAA. The physicochemical properties, such as melting point, magnetic susceptibility, and molar conductivity at room temperature, were determined. The synthesized complexes C1, C2, and C3 have taken the octahedral geometry in a mole ratio (1:1) of M: L and behave as bidentate ligands that attach to metal ions through the N atom of azomethine and the S atom in the thione group. The metal complexes displayed an octahedral geometry around bivalent cobalt, nickel, copper (II), and zinc (II) tetrahedral environments. Moreover, the biological activity of free ligand and its metal complexes solutions (CoL and CuL) was screened against some bacteria and fungi. The free ligand and CuL were more active against bacteria and fungi than CoL. These results can provide an important platform for the design of new compounds with antibacterial and antifungal activity.

As well as this, the study included examining the antioxidant activity of the synthesized metal complexes (ZnL and CuL) using DPPH assay against ascorbic acid as a reference antioxidant agent. The results showed that all the synthesized metal complexes have antioxidant activity but lower than ascorbic acid. As well as the zinc (II) complex, it was found to have higher antioxidant activity than the Cu (II) complex. The highest free radical scavenging capacity of the zinc (II) complex and Cu (II) complex at 500 µg/ml were 75.670 % and 69.409%, respectively