Design and synthesis of nickel(II) and palladium(II) complexes bearing imine ligands: Spectral characterization, hirshfeld and biological studies

Abstract

Four Ni(II) and Pd(II) complexes in a series have been synthesized with chelating imine ligands that have been coordinated to metal centres with ONO and ONS donor atoms. The ligands and complexes are characterized with spectroscopic techniques like FT-IR, NMR, HRMS, and UV–visible spectroscopy. The single crystal structure of Ni(II) and Pd(II) complexes were obtained by X-ray diffraction analysis and exhibits slightly distorted square planar geometry. X-ray diffraction measurements support the crystalline structures of the metal complexes rather than the amorphous form of the parent imine ligands. To further explain the electronic structure and stability of the Ni(II) and Pd(II) complexes, the structures are optimized using DFT calculations. Additionally, the antimicrobial efficacies of the imine ligands and their corresponding metal complexes were screened against Staphylococcus aureus as a gram-positive bacteria, Escherichia coli as a gram-negative bacteria, and the fungi Aspergillus niger and Candida albicans. The antimicrobial inhibitory data revealed higher activities of metal complexes compared to their imine ligands. Furthermore, molecular docking to the SARS-CoV-2 protein was used to examine the binding capabilities against 7JP1 of synthesized compounds. According to the molecular docking data, all of the synthesized complexes had strong binding affinities for the 7JP1 protein. Overall, this study offers insightful information about the stability of the complexes and their intriguing applications in the pharmaceutical field.