Synthesis, Characterization, and Antimicrobial Activities of (E)-2-(2-aminothiazol-4-yl)-N'-(2-nitrobenzylidene)acetohydrazide Ligand and Its Co(II) Complex

Abstract

The biological and pharmacological applications of Hydrazone Schiff base ligands and their metal complexes have been the focus of recent research, aiming to mitigate the effects of multidrug-resistant bacterial and fungal infections. This study aimed to synthesize, characterize, and evaluate the antimicrobial activities of a hydrazone Schiff base ligand, (E)-2-(2-aminothiazol-4-yl)-N'-(2-nitrobenzylidene)acetohydrazide, and its Co(II) complex, in order to explore their potential as antimicrobial agents. The ligand was synthesized by condensing 2-(2-aminothiazol-4-yl)acetohydrazide with 2-nitrobenzaldehyde in ethanol, while the Co(II) complex was prepared in a 1:2 metal-to-ligand ratio. Both compounds were characterized by FTIR, UV–Vis, ¹H NMR, XRD, and GC–MS. Antimicrobial activities were assessed by disc diffusion, minimum inhibitory concentration (MIC), and minimum bactericidal/fungicidal concentration (MBC/MFC) methods against Escherichia coli, Salmonella typhi, Staphylococcus aureus, Streptococcus pyogenes, and Candida albicans.The ligand and its Co(II) complex were obtained in yields of 55.2% and 70%, with melting points of 150°C and 155°C, respectively. Spectroscopic and diffraction studies confirmed successful synthesis and coordination. The ligand exhibited moderate antibacterial activity but limited antifungal efficacy, whereas the Co(II) complex displayed broader activity, with zones of inhibition reaching up to 20 mm and lower MIC values (250–500 μg/mL). Neither compound demonstrated bactericidal/fungicidal effects (MBC/MFC: not detected). Coordination with Co(II) enhanced the antimicrobial spectrum of the Schiff base ligand, suggesting potential as a lead for further antimicrobial drug development.