Structural investigations of new tridentate-phenylacetohydrazide Schiff base metal chelates: X-ray diffraction, Hirshfeld surface analyses, DFT, antibacterial and molecular docking studies

The coordination complexes of a tridentate-phenylacetohydrazide Schiff base (2-hydroxybenzylidene-2-phenylacetohydrazide, HL) with metal ions, namely, iron(II), zinc(II), palladium (II), silver(I) and cadmium(II), were synthesized and investigated using various analytical and spectroscopic techniques. A single-crystal X-ray diffraction analysis was performed on the silver derivative. The HL ligand and Ag complex were also characterized via Hirshfeld surface analyses. Both X-ray and Hirshfeld surface analysis revealed intriguing structure and geometric characteristics, as well as remarkably intramolecular and intermolecular hydrogen bonding. All metal ions, with the exception of palladium one, bonded to two molecules of ligand without deprotonation of the hydroxyl moieties. In addition, 1H NMR studies of the diamagnetic complexes and X-ray analysis of the silver complex revealed the presence of the unprotonated OH. DFT-B3LYP calculations were used to determine the energy-minimized molecular geometric arrangements of the Pd(II), Ag(I), and Cd(II) derivatives. Quantum global reactivities of the complexes were also computed. Antibacterial and molecular docking studies of complexes were carried out to examine the potential applications of derivatives as therapeutic reagents. The Ag(I) complex showed the highest antibacterial inhibition towards the tested bacteria with zone diameter = 21.7, 21.0, 19.3 and 15.7 mm. Molecular docking analysis revealed that the complexes have high binding affinities against the selected receptors (PDB: 1BNA and 5AEP) and demonstrated different DNA binding potencies.