A series of novel 5-amino-1,3,4-thiadiazole-2-thiol and 1,3,4-thiadiazole-2,5-dithiol derivatives of benzimidazole were synthesized through nucleophilic substitution reaction of 5-substituted-2-(chloromethyl)-1H-benzimidazole, structures of the synthesized compounds were proved by spectral methods of analysis ( FT-IR, 1 H and 13 C NMR ). All the target compounds were screened for their antibacterial activity toward gram-negative (E.coli, P. aeruginosa) and Gram-positive (B. subtilis, S. aureus) bacteria, most of the synthesized derivatives exhibited good to moderate activity toward both Gram-positive (B. subtilis, S. aureus) and Gram-negative (E.coli, P. aeruginosa) bacteria.

Serious of some novel bis benzimidazole derivatives were designed and synthesized by nucleophilic substitution reaction of 5-(un)substituted-2-chloromethyl-1H-benzimidazole and 5-(un)substituted-2-mercapto-1H-benzimidazole in the presence of sodium in methanol. Spectral methods of analysis (FT-IR, 1H-NMR, and 13C-NMR) were used to confirm the structures of the synthesized compounds. Antibacterial activity were evaluated for most of the target compounds against four strains of bacteria including ( E.coli, P. aeruginosa ) as gram-negative bacteria and ( B. subtilis, S. aureus ) as gram-positive bacteria, the tested compounds showed various activity against both gram-negative and gram-positive bacteria used.

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Two Schiff base ligands L1 and L2 have been obtained by condensation of salicylaldehyde respectively with leucylalanine and glycylglycine then their complexes with Zn(II)were prepared and characterized by elemental analyses , conductivity measurement , IR and UV-Vis .The molar conductance measurement indicated that the Zn(II) complexes are 1:1 non-electrolytes. The IR data demonstrated that the tetradentate binding of the ligands L1 and L2 . The in vitro biological screening effect of the investigated compounds have been tested against the bacterial species Staphlococcus aureus, Escherichia coil , Klebsiella pneumaniae, Proteus vulgaris and Pseudomonas aeruginosa by the disc diffusion method . A comparative study of inhibition values of the Schiff base ligands and their complexes indicated that the complexes exhibit higher antimicrobial activity than the free ligands . Zinc ions are proven to be essential for the growth-inhibitor effect. The extent of inhibition appeared to be strongly dependent on the initial cell density and on the growth medium .

A new series of benzimidazole containing Schiff base moiety has been synthesized. The reaction was achieved through cyclocondensation reaction of the substituted 1,2-phenylenediamines and amino acids (glycine, alanine and tyrosine) to gave substituted benzimidazole derivatives 1(a-f). Asian Journal of Chemistry; Vol. 30, No. 2 (2018), 381-385 EXPERIMENTALMelting points were taken in an electrically heated using Stuart SMP3 instrument and are uncorrected. FT-IR spectra were recorded on Shimadzu (FTIR-8400 S) Infrared spectrophotometer by KBr disc. The