Synthesis, characterization, and antibacterial activity of Benzimidazole Schiff Bases and Bis(thiazolidin-4-one) Derivatives
College of Pharmacy, University of Tikrit.
World Journal of Chemical and Pharmaceutical Sciences, 2026, 09(01), 026–040.
Article DOI: 10.53346/wjcps.2026.9.1.0023
Publication history:
Received on 07 June 2026; revised on 14 July 2026; accepted on 16 July 2026
Abstract:
A sequential synthetic route was developed for the preparation of benzimidazole-linked Schiff bases and bis(thiazolidin-4-one) derivatives. 4-(1H-Benzimidazol-2-yl)aniline (H1) was obtained by acid-promoted cyclocondensation of o-phenylenediamine with 4-aminobenzoic acid. Condensation of H1 with 4-aminoacetophenone afforded the mono-Schiffbase H2 while retaining a free para-amino group. Subsequent reactions of H2 with 4-methylbenzaldehyde and 4-bromobenzaldehyde yielded the bis-Schiff bases H3 and H4, respectively. Cyclization of H3 and H4 with thioglycolic acidin the presence of anhydrous zinc chloride produced the corresponding bis(thiazolidin-4-one) derivatives H5 and H6.The structures were evaluated using FTIR and NMR spectroscopy. Schiff-base formation was supported by theappearance of imine-related signals and the disappearance of the residual amino-group pattern after the secondcondensation, whereas ring closure was evidenced by thiazolidinone carbonyl absorptions and new aliphaticresonances assigned to the five-membered rings. Antibacterials activity is evaluate by the agar well diffusions methodagainst Escherichia coli and Staphylococcus aureus. The cyclize derivatives H5 and H6 produced larger inhibitions zonesthan their Schiff-base precursors, and H6 showed the greatest activition, with inhibition-zone diameters of 24 and 26mm against E. coli and S. aureus, respectively. These findings indicate that thiazolidin-4-one ring formation and the para-bromo substituent enhance the antibacterial response within the investigated series.
Keywords:
Benzimidazole; Schiff Base; Thiazolidin-4-One; Thioglycolic Acid; FTIR; NMR Spectroscopy; Antibacterial Activity; Agar Well Diffusion
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