Preparation of lanthanum and nickel complexes based on a newly prepared Schiff base ligand: Structural elucidation, molecular docking, and density functional theory calculations

ligand derived from the condensation reaction of 4-aminoantipyrine, 5-bromosalicylaldehyde, and o-phenylenediamine.
The Schiff base ligand was characterized using various spectroscopic techniques, such as 1H and 13C
NMR spectroscopy, and UV–visible spectral studies, to confirm its structure and purity. The metal complexes
were prepared by reacting the ligand with LaNO3.6H2O and NiCl2.6H2O under reflux conditions, and their
structural properties were determined through 1H and 13C NMR spectroscopy. Density Functional Theory (DFT)
calculations were employed to investigate the geometry and electronic structure of the complexes, providing
insights into their stability, frontier molecular orbitals (HOMO-LUMO), and reactivity indices. DFT analysis
showed that the La complex forms the strongest bond with the ligand, indicated by its higher binding energy
compared to the Ni complex. HOMO and LUMO energy gap levels indicate that the Ni complex is the most
reactive compound, while the La complex exhibits lower reactivity due to its larger energy gap. Molecular
docking studies were conducted to assess the biological activity of the Schiff base ligand and its complexes
against the active sites of Entamoeba coli (ID: 1C14) as Gram-negative bacteria, Staphylococcus aureus (ID: 2XCT)
as Gram-positive bacteria, and Xanthine oxidase (ID: 1FIQ) as an antioxidant agent protein-selected biological
target, revealing strong binding interactions that suggest potential applications as antimicrobial or anticancer
agents. Overall, this study demonstrates the successful synthesis and characterization of Lanthanum and Nickel
complexes, supported by computational analyses, and highlights their promising biological relevance, opening
up avenues for further research in medicinal chemistry and materials science.