Synthesis, characterization, antioxidant and bioactivity assessment, and thermodynamic analysis of metal ion complexes using a novel azo dye

In this study, the new azo dye,5,5-[1,2-phenylenebis(2,1-biazenediyl)] bis[8-quinolino], was used to synthesize complexes with Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Cd²⁺ ions. The compounds were characterized using ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, mass spectrometry, thermo gravimetric analysis (TGA), diffevential scanning calovimltry (DSC), CHN analysis. Further, conductivity, magnetic susceptibility, and metal and chlorine content analysis using FT-IR spectroscopy revealed that the ligand chelates as a bidentate (OH) phenol group and a bidentate (CN) ring group. The ligand exhibited tetradentate behavior, forming tetrahedral complexes. Except for Co and Ni complexes,whichare octahedral, all of them are non-electrolytes. Air-stable complexes with distinct octahedral moieties were created in a 2:1 metal:ligand molar ratio. The effectiveness of both the compounds in inhibiting free radicals was evaluatedbased on their ability to act as antioxidants was assessed using 2,2-diphenyl-1-picrylhydrazyl (DPPH) as a free radical and gallic acid as a standard substance. The IC₅₀ value indicated that the ligand had higher free radical inhibition ability, and the ability to inhibit the compoundsvaried.The ligand and complexes with Co²⁺, Cu²⁺, and Zn²⁺ were tested against Escherichia coli, Bacillus spp, Penicillium, Aspergillus niger, Fusarium, and Trichoderma at two concentrations, showing varying inhibitory effects on bacterial and fungal growth compared to the control.