Synthesis and characterization of azo-schiff bases containing thiadiazole moiety of biological interest

Abstract

Azo compounds or azo dyes are characterized by the presence of the azo moiety (-N=N-) in their structure conjugated with two distinct or identical mono or polycyclic aromatic or heteroaromatic systems. Because of their specific physico-chemical properties and biological activities, they have a broad spectrum of application in the field of pharmaceutical, textile industry, and in analytical chemistry. However the most typical and popular field of utility remains as their coloring function. The Azo compounds are applicable for biocidal treatment of textile materials because they exhibit biological activity. Azo compound are well known for their medicinal importance and are recognized for their applications as anti-diabetics, antiseptics, anti-neoplastics, antibacterial and anti-tumor. They are also involved in many biological reactions such as inhibitions of DNA and RNA, carcinogenesis, protein synthesis and nitrogen fixation. The azo-imine linkage is responsible for the biological activities are displayed by some Schiff bases. On the other hand, the 1, 3, 4-thiadiazole nucleus is one of the most important and well-known heterocyclic nuclei, which is a common and integral feature of a variety of natural products and medicinal compounds. Thiadiazole nucleus is present as a core structural component in an array of drug categories such as anti-microbial, anti-inflammatory, anticancer, antiviral and anti-tubercular agents. The broad and potent activity of thiadiazole and their derivatives have established them as pharmacologically significant scaffolds. Therefore, the combination of bis-azo and thiadiazole has received considerable attention to synthesize bis-azo-schiff bases containing thiadiazole moiety.

The thiadiazole derivatives were synthesized from aromatic aldehydes and thiosemicarbazide. Then azo compounds were prepared by the conventional diazocoupling reaction using diazonium salts and salicyldehyde. Finally the bis-azo-imine compounds were synthesized from thiadiazole and bis-azo compounds. Synthesized compounds were characterized by FT-IR, 1H NMR and 13C NMR. The newly synthesized compounds showed moderate to good antibacterial property against S. aureus, B. cereus and E.coli.

R= (NO2, Cl, OH, H)

Scheme: Azo-Schiff Bases Containing - 1, 3, 4-thiadiazol moiety