The biological activities of 1, 3, 4-thiadiazole have been reviewed in the last few years. 2,5-di (Mercapto-aceticester)-1.3.4-thidiazole (2) prepared from 2, 5 – Dimercapto -1, 3, 4-thiadiazole was treated with hydrazine hydrate in methanol to yield 2,5-di (Mercapto-acetic hydrazide)-1.3.4-thidiazole (3).The condensation of compound 3 with various aromatic aldehyde yielded the corresponding Schiff bases of substituted 2,5 – Dimercapto -1,3,4-thiadiazoles(4a-j). The structures of the Schiff bases were elucidated by IR, 1H- and 13C -NMR spectral measurements. The target compounds 4a-j was screened for their in vitro antimicrobial activity and the Minimum Inhibitory concentration of each compound was determined by liquid broth method. From newly synthesized series of compounds 4f and 4j exhibited significant antimicrobial potential against Staphylococcus aureus and Bacillus substilis (gram-positive), Escherichia coli and Salmonella enteritidis (gram-negative) bacteria. The compounds also showed significant antifungal activity against Candida albicans, Trichophyton rubrum, Trichoderma viride and Aspergillus flavus.
