Synthesis of 1,5 and 2,5-disubstituted tetrazoles using NiO nanoparticles and their evaluation as antimicrobial agents

Treatments of tetrazolate salts, malononitrile and sodium azide using NiO nanoparticles with benzyl bromide gave the corresponding 1,5- and 2,5-disubstituted tetrazoles. Reaction of tetrazolate salts with 2,4′-dibromoacetophenone by NiO nanoparticles provided 2,5-disubstituted derivatives as an only isomer. The structures of tetrazoles were characterized by 1 H and 13C NMR spectra, FT-IR spectra, MS and elemental analysis. Use of simple and readily accessible starting materials, excellent yields, reusability of the catalyst, short reaction times, low amount of catalyst are some advantages of this protocol. Their antimicrobial activity has been tested in vitro against Gram positive bacteria; Gram negative bacteria and fungi. Four compounds have only moderate growth inhibitory effects against Gram positive bacteria. The antimicrobial screening suggests that compounds 5h; 6h; 5g and 6g have only medium growth inhibitory effects against Gram positive bacteria. Among the newly synthesized compounds; good antimicrobial activity was observed for compound 6g against Staphylococcus epidermidis (MIC value 125 µg/ml).