Novel Copper (II) Complex Derived from Sulfadiazine Azo Resorcinol Ligand: Characterization, Antibacterial Evaluation, and Molecular Docking Study.

Abstract

A novel copper complex was synthesized from a heterocyclic azo ligand, namely Sulfadiazine Azo Resorcinol (SAR). The first step involved preparing the azo ligand using a classical diazotization-coupling method. The copper complex was subsequently prepared with a 1:2 metal-to-ligand molar ratio. Following purification, the prepared ligand and its Cu(II) complex were characterized using FT-IR spectroscopy, UV-Vis spectroscopy, ¹H-NMR spectroscopy, CHN elemental analysis, molar conductivity, and magnetic susceptibility. The analytical results indicated that the ligand coordinated as a bidentate (N, O) donor, binding with two ligand molecules and two coordinated water molecules to the copper center, resulting in a neutral octahedral geometry. The antimicrobial activity of both the free ligand and its complex was evaluated against five pathogenic bacterial strains (E. coli, P. aeruginosa, S. aureus, E. faecalis, and P. agglomerans) using the agar well diffusion method. Biological activity evaluations demonstrated that both compounds exhibited moderate to high antimicrobial activity, with the copper (II) complex displaying significantly enhanced activity compared to the free ligand. Furthermore, a molecular docking simulation was conducted to evaluate the binding modes, affinities, and specific intermolecular interactions of the synthesized compounds within the active binding pockets of key bacterial target proteins. Two target proteins were selected for the docking study: dihydropteroate synthetase (PDB ID: 1AD4) and Dihydropteroate synthetase from E. coli (PDB ID: 3TYU). The molecular docking results were consistent with the in vitro antibacterial findings; the Cu(II) complex exhibited higher binding affinity toward both target proteins than the free ligand.