In this study, a new Azo ligand 5-((2-(1H-indol-2-yl)ethyl)diazinyl)-2-aminophenol is synthesized from a reaction of Tryptamine with 2-aminophenol. The ligand and their metal ion complexes Ni(II), Pd(II) , Pt(IV) and Au(III) have been synthesized and characterized by various analytical techniques, including elemental microanalysis, metal content, chloride-containing, measurement of electrical conductivity, magnetic susceptibility, 1H and 13C-NMR, FT-IR, UV-Vis, mass spectra (MS), and thermal analysis (TGA and DSC) curves. The DCS curve was used to calculate the thermodynamic parameters ΔH, ΔS, and ΔG. The characterization results promote the metal complexes of azo ligand structures. The results indicate that the ligand behaves as a trident N, N, and O donor ligand for each and every produced complex, and the molar conductivity of all complexes indicates that none of the complexes were electrolytes. The antioxidant activity of the synthesized compounds was evaluated and determined against the DPPH radical (1.1-diphenyl-2-picrylhydrazyl) and compared to that of a standard natural antioxidant, gallic acid. The results show that the metal complexes are more effective at scavenging free radicals.
