Spectroscopic, Structural Analysis, Molecular Orbital, Molecular Docking, and Antibacterial Activity of the Thiocarbohydrazone Ligand and Its Complexes

Abstract

New thiocarbohydrazone ligand (N′-((E)-3,3-diphenyl-2,3-dihydro-1H-inden-1-ylidene)-2-((Z)-2-oxoindolin-3-ylidene)hydrazine-1-carbothiohydrazide; H₂L) and its Co (II), Ni (II), Fe (III), Cu (II), Cd (II), Zn (II), and Mn (II) complexes were prepared in good yields ranging from 60% to 90% and characterized by spectroscopic and analytical tools. Uv–vis, magnetic measurements, molar conductivity, ¹H-NMR spectra, elemental analyses, and FT-IR were performed. The structural formula for the examined ligand was improved using the Gaussian09 tool. The morphology of the thiocarbohydrazone ligand and metal complexes was demonstrated using a scanning electron microscope. The prepared thiocarbohydrazone ligand and its complexes were evaluated for their antimicrobial properties against Streptococcus mutans and Staphylococcus aureus as G-positive bacteria; Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa as G-negative bacteria; and some species of fungi as Aspergillus niger and Candida albicans. It was found that thiocarbohydrazone ligand was less biologically active than the targeted complexes as indicated from the obtained inhibition zone diameters. The interaction between the ligand and the amino acids of the proteins of G-positive bacteria (Staphylococcus typhus-3ty7), G-negative bacteria (E. coli-3t88), and fungi (C. albicans-5k04) as receptors was investigated using molecular docking study to correlate the experimental and theoretical observations.