A new heterocyclic azo dye ligand (L) was synthesized by the combination of 4-amino antipyrine with 4-aminophenol. The new Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) complexes were synthesized in excellent yields. The metal chelate structures were elucidated using elemental analyses, FT-IR, ¹H-NMR, mass, magnetic moment, diffused reflectance spectral and thermal analysis (TG-DTG), and molar conductivity measurement. According to the FT-IR study, the azo dye ligand exhibited neutral tri-dentate behavior, binding to the metal ions with the azo N, carbonyl O, and protonated phenolic OH. The ¹H-NMR spectral study of the Zn(II) complex supported the coordination of the zo dye ligand without proton displacement of the phenolic OH. Diffused reflectance and magnetic moment studies revealed the octahedral geometry of the complexes, as well as their good electrolytic nature, excepting the Zn(II) and Cd(II) complexes, which were nonelectrolytes, as deduced from the molar conductivity study. The theoretical calculations of optimized HOMO–LUMO energies, geometrical parameters, electronic spectra, natural atomic charges, 3D-plots of MEP, and vibrational wavenumbers were computed and elucidated using LANL2DZ and 6-311G (d, p) basis sets of density functional theory (DFT) with the approach of B3LYP DFT and TD-DFT methods. The ligand and complexes have been assayed for their antimicrobial activity and compared with the standard drugs. Most of the complexes have manifested excellent antimicrobial activity against various microbial strains. A molecular docking investigation was also performed, to acquire more information about the binding mode and energy of the ligand and its metal complexes to the Escherichia coli receptor using molecular docking. Altogether, the newly created ligand and complexes showed positive antibacterial effects and are worth future study.

Cupric oxide—chitosan nanocomposite was prepared in aqueous solution. Copper ions were adsorbed into the chitosan mainly by chelation to form copper-loaded chitosan. Copper-loaded chitosan was reduced by using sodium hydroxide at specific pH. Copper oxide nanoparticle-loaded chitosan was formed by oxidation of Cu(OH)₂-loaded chitosan by using drops of H₂O ₂ (30%). CuO nanoparticles-loaded chitosan molecules were stirred with a high-speed homogenizer at 10,000 rpm for 30 minutes. The corresponding CuO/chitosan nanocomposite formed was characterized by using transmission electron microscope images. The copper oxide/chitosan nanocomposite was applied to cotton fabric by using pad-dry cure technique. Cotton fabric treated with CuO—chitosan nanocomposite was characterized via scanning electron microscope supplied with energy dispersive spectroscopy to verify the elemental composition of deposited materials on the fabric. Antimicrobial activity of the prepared fabric samples treated with chitosan nanoparticles and CuO/chitosan nanocomposites against Gram-positive bacteria (Staphylococcus aurous) and Gram-negative bacteria (Escherichia coli) were investigated. Durability of treated cotton fabrics with nanocomposites has been evaluated.