Synthesis, spectroscopic elucidation, density functional theory calculation, and molecular docking studies of a novel series of tetradentate macrocyclic Schiff base ligands and their Zn(II) complexes and investigations of their antimicrobial, anti-inflammatory, and anticancer activities

In the present work, novel Schiff base macrocyclic Zn(II) complexes [Zn(N(8)O(4)MacL(1))Cl-2-Zn(N(8)O(4)MacL(3))Cl-2] were synthesized by the reaction of ZnCl2 and macrocyclic ligands (N(8)O(4)MacL(1)-N(8)O(4)MacL(3)) derived from the condensation of ligand (L) and dicarboxylic acids [HOOC-(CH2)(n)-COOH]. The structural confirmation of the newly synthesized compounds was accomplished through various analytical techniques, including elemental analysis, infrared (IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS), UV-visible spectroscopy, and powder X-ray diffraction (XRD) studies. The spectral data provided evidence that the macrocyclic ligands acted as tetradentate ligands, forming coordination bonds with Zn(II) ions through the nitrogen atom of the imine (>C=N) group. The coordination complexes exhibited an octahedral geometry around the zinc ion, with two chloro groups covalently attached. Density functional theory (DFT) studies of the synthesized Schiff base macrocyclic compounds were carried out to determine their structural and electronic properties. The antimicrobial potential of the macrocyclic compounds was examined against a panel of pathogenic microbes, including four bacterial strains (Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Xanthomonas campestris) and two fungal strains (Fusarium oxysporum and Candida albicans). Then, the newly synthesized Schiff based macrocyclic compounds were evaluated for their anti-inflammatory activity using an egg albumin method. The synthesized compounds were subjected to further evaluation to assess their potential as anticancer agents against MCF-7 (human breast adenocarcinoma cell line), HCT-116 (human colon cancer cell line), and A549 (human alveolar adenocarcinoma epithelial cell line). In addition, molecular docking studies were conducted to explore the potential interactions between the synthesized compounds and the target proteins VEGFR2 (PDB ID 1YWN), EGFR (PDB ID 1M17), and DNA gyrase B (PDB ID 4URO). It was found that there was a high correlation between the experimental results and the docking calculations.

Automated summary

Novel Schiff base macrocyclic Zn(II) complexes were synthesized and their structures were confirmed using various analytical techniques. The macrocyclic ligands acted as tetradentate ligands, forming coordination bonds with Zn(II) ions. The coordination complexes exhibited potential in antimicrobial, anti-inflammatory, and anticancer activities. The docking studies showed good correlation with the experimental results.