10.22376/ijpbs.2019.10.1.p1-12 Volume 5 Issue 1 2014 (January - March) A synthesis of 2-Isonicotinyl 3, 5-diaryl -2H-(3-tetrazolium) chloride (5) was performed starting from isonicotinic hydrazide (1). The treatment of 1 with various substituted aromatic aldehydes afforded the corresponding Schiff's bases 3. The Schiff's bases are converted into a series of aryl formazan via diazocoupling which underwent cyclization in the presence of H lessThan sub greaterThan 2 lessThan /sub greaterThan O lessThan sub greaterThan 2 lessThan /sub greaterThan and KMnO lessThan sub greaterThan 4 lessThan /sub greaterThan to give substituted tetrazolium derivatives. The titled compounds were characterized physically and analysed structurally by spectroscopic techniques and Elemental analysis. The compounds S lessThan sub greaterThan 1 lessThan /sub greaterThan -S lessThan sub greaterThan 12 lessThan /sub greaterThan were screened for antibacterial activity against lessThan i greaterThan Escherichia coli(ATCC 14580), Bacillus subtilus(ATCC 700294) and Staphylococcus aureus(ATCC14580) lessThan /i greaterThan , anti fungal activity against lessThan i greaterThan Aspergillus niger( NCIM 627) lessThan /i greaterThan and anti oxidant activity by DPPH method. All the compounds exhibited significant antimicrobial activity and the compound 2-isonicotinoyl-5-(4-methoxyphenyl)-3-(4-sulfamoylphenyl)-2H-(3-tetrazolium) chloride (S lessThan sub greaterThan 3 lessThan /sub greaterThan ) revealed good inhibitory activity against bacterial and fungal strains. The presences of electron withdrawing substituents in the phenyl ring at 3 and 5 position of tetrazole resulted in more potent compounds for the above evaluated activities. P.VALENTINA , K.ILANGO AND G.DEEPA INH, Tetrazole, DPPH, Schiff’s base 70-75