Synthesis, Characterization, DFT Computation, Molecular Docking, and Biological, Environmental, and Electrochemical Applications of Quinoline-2-Carboxaldehyde-Based Schiff Base and Its Nanometal Chelates

Abstract

A Schiff base ligand (L) is synthesized and characterized using quinoline-2-carboxaldehyde and 2-aminobenzimidazole. Metal complexes of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), and Cd (II) ions are produced and studied utilizing IR, ¹H-NMR, UV–visible, mass spectrometry, and molar conductivity measurements. Schiff base ligand was found to be bidentate. Based on spectroscopic, elemental, and magnetic tests, the complexes were octahedral. Mn(II), Co(II), Zn(II), and Cd(II) complexes have poor molar conductivity. Ionic Cr(III), Fe(III), Ni(II), and Cu(II) complexes are 1:1 electrolytes. Using thermogravimetric (TG) analysis, the Schiff base ligand (L) and its complexes' thermal characteristics are evaluated from room temperature to 1000°C. Scanning electron microscope (SEM), atomic force microscope (AFM), and BET surface area data showed that the Co(II) and Cu(II) complexes exhibited nanometric structures with reasonable surface area. Schiff base ligand and its Co(II) and Cu(II) complexes were theoretically optimized for molecular and electronic structures. Additionally, quantum chemical parameters were calculated. Molecular docking screening predicted Schiff base ligand-receptor binding efficiency. Candida albicans (5JPE) and Staphylococcus aureus (1GHP) receptors interacted best with Schiff base ligand. Schiff base ligand and its metal complexes were tested against Gram-positive (Staphylococcus aureus and Streptococcus mutans) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumonia). The compounds were also tested for antifungal activity against Candida albicans and Aspergillus niger. The complexes outperformed the ligand in antibacterial activity, suggesting they could be antimicrobial medications and warranting further study. The best conditions for Cu(II) nanocomplex photocatalytic activity were low pH and 10 min, which degraded 85% of rose bengal dye (RBD) from aqueous solutions. Electrochemical detection of arsenic anions utilizing Co(II) nanocomplex using cyclic voltammetry was tested.