Synthesis, Structural Characterization and Biological Studies of Schiff Base Complexes Bearing Indole Moiety

Abstract

Schiff base complexes of N₂O₂ type derived from indole-3-carboxaldehyde(ind) and amino acids such as glycine(gly), L-valine(val), and L-tryptophan(try) with Cu(II), Ni(II), Zn(II), Co(II) and Mn(II) were synthesized and characterized by physical and analytical techniques. The complexes are of non-electrolytic nature having 1:2 (metal:ligand) ratio. The geometry of the complexes was predicted with the combined data obtained from electronic spectral and magnetic susceptibility measurements. The mode of coordination of the Schiff base ligands with the metal ions is through the carboxylate oxygen and the azomethine nitrogen as confirmed by FT-IR spectra. The cyclic voltammogram of the Cu(II) complexes exhibit Cu(II)®Cu(I) peak in the cathodic side and the corresponding quasi-reversible type peak is obtained in the anodic side. The thermal behavior (TG/DTA) of the synthesized complexes shows that the complexes loose water molecules in the first step followed by decomposition of the ligand, which follows first order kinetics. The SEM analysis reveals the particle size and the morphology of the complexes. The X-band EPR spectrum of Cu-indgly complex in DMSO solution at 300 and 77 K was recorded. The calculated g tensor values agree with the geometry proposed by the electronic absorption spectral measurements. The M-indval complexes were studied for their cleaving ability with calf thymus DNA by gel electrophoresis method. The antibacterial activity of the Schiff base metal complexes was tested in vitro against some common bacteria using ampicillin as control. Antifungal activities were determined using nystatin as control. The results are compared with control; most of the metal chelates exhibited higher biological activities.

Keywords: 

indole-3-carboxaldehyde, Schiff base complexes, cyclic voltammetry, biological activity, DNA cleaving activity