Synthesis, Spectral Characterization, Structural Elucidation, and Antibacterial Evaluation of a Tridentate Hydrazone–Oxime Schiff Base Ligand and Its Lanthanide (III) Complexes
Year: 2026
Type: article
Abstract: A novel hydrazone–oxime Schiff base ligand, (E)-N-((E)-2-bromobenzylidene)-2-((E)-2-(hydroxyimino)-1,2-diphenylethylidene)hydrazine-1-carbothioamide (MKL1), was successfully synthesized via condensation of α-benzilmonoximethiosemicarbohydrazide with o-bromobenzaldehyde in ethanolic medium. The ligand was obtained in high yield and purity and subsequently employed for the preparation of a series of lanthanide(III) complexes. Comprehensive characterization using UV–Vis, FT-IR, 1H and 13C NMR, elemental analysis, HRMS, magnetic susceptibility, and X-ray diffraction techniques confirmed the proposed formulations. Spectroscopic investigations revealed that MKL1 behaves as a monoanionic tridentate N, O, S donor, coordinating through azomethine nitrogen, deprotonated oxime oxygen, and thioamide sulfur atoms to form stable tris-chelated lanthanide(III) complexes with octa-coordinated geometry. Electronic spectral features and calculated bonding parameters suggested weak but appreciable covalent character in metal–ligand interactions. XRD analysis confirmed the crystalline nature of the complexes with nanoscale crystallite sizes. The antibacterial activity of the ligand and its metal complexes was evaluated against selected Gram-positive and Gram-negative bacterial strains. While the free ligand exhibited modest activity, metal complexation led to a significant enhancement in antibacterial efficacy, in several cases surpassing that of streptomycin. The improved biological performance is attributed to chelation-induced increases in lipophilicity and effective metal–ligand synergy. These findings highlight the potential of lanthanide Schiff base complexes as promising antimicrobial agents.
Author: Sharad Sankhe, Madhuri Kamble*
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,620
OpenAlex ID: W7168662468