Three Schiff base compounds were prepared from the reaction of acetophenone and o-phenylene diamine, p-phenylene
diamine and benzoimidazole designated as (AH1-AH3). The products were reacted by dimethyl sulfate to obtain three
diSchiff base cationic derivatives (AH4-6). The chemical structures of the prepared diSchiff bases and their cationic
derivatives were confirmed using elemental analysis, infrared spectroscopy and nuclear magnetic resonance spectra. The
prepared cationic derivatives were evaluated for their antimicrobial activities against Gram-positive, Gram-negative and
sulfate reducing bacteria. The evaluation was involved inhibition zone diameter and minimum inhibitory concentration
measurements. The results showed that the chemical structures of the compounds play an effective role on their
antimicrobial efficiency.