Synthesis, characterization, and antimicrobial evaluation of Fe(III) and Ni(II) complexes derived from azo-chalcone ligand: Spectroscopic, thermal, and molecular docking investigations

This study reports the design, synthesis, structural characterization, and antimicrobial evaluation of novel iron(III) and nickel(II) metal complexes derived from a newly developed azo-chalcone-based organic ligand. Comprehensive structural elucidation was performed using a range of spectroscopic and analytical techniques, including infrared spectroscopy, ultraviolet–visible spectroscopy, proton nuclear magnetic resonance spectroscopy, mass spectrometry, elemental analysis, molar conductivity measurements, and magnetic susceptibility analysis. The results confirmed coordination of the ligand to the metal centers through azo and phenolic functional groups, and indicated an octahedral geometry for both metal complexes. The non-electrolytic nature of the complexes was verified by conductivity studies, while elemental analysis established a metal-to-ligand stoichiometry of 1:1. Thermal analysis demonstrated high thermal stability and suggested the presence of coordinated water molecules. Biological assays revealed significantly enhanced antimicrobial activity of the metal complexes compared to the free ligand, with the nickel(II) complex showing the highest antibacterial effectiveness, particularly against Pseudomonas aeruginosa. This enhanced bioactivity is attributed to increased lipophilicity and improved interaction with microbial cell membranes. Furthermore, molecular docking studies demonstrated that metal coordination significantly improved the binding affinity of the complexes to bacterial target proteins, with the nickel(II) complex showing the strongest binding interaction. These findings suggest the potential of metal complexation as a strategy to enhance the pharmacological properties of bioactive ligands.