Synthesis, characterization, and fluorescent sensing of a decadentate macrocyclic ligand: DFT, antioxidant, and antibacterial insights

A decadentate macrocyclic ligand with two piperazine, two pyrrole, and one pyridine moieties was synthesized by the condensation reaction of a prepared polyamine with a prepared dialdehyde. The compound was characterized by elemental analysis, mass spectroscopy, FT-IR, 1 HNMR, and UV–Vis spectroscopy. Then fluorescence studies were carried out to investigate the sensing properties of the ligand. It was indicated that the ligand can detect Zn (II) ions among 18 other metal ions. The detection limit for Zinc metal ions is 2.8 × 10 −9 M which is far below the guidelines of the World Health Organization. Density functional computations were performed at the BP86/def2-SVP level of theory. It was found that the complex band gap is smaller than the ligand. So, its reactivity is much more than the ligand, and charge transfer can easily take place within the system. According to the theory, the ligand and its corresponding zinc complex have good nonlinear optical properties and might be considered as NLO materials. The ligand and its complex, which were evaluated by measuring their abilities to scavenge the DPPH-radical exhibited significant antioxidant potency. Antibacterial activity of the compounds was assessed using the disc diffusion method against bacterial strains including Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus. The results indicated that the complex demonstrated a greater antibacterial activity than the ligand.