Benzimidazole-acrylonitriles as chemosensors for picric acid detection

Sensitive detection of nitroaromatic explosives such as picric acid is critical. Among various known methods, materials exhibiting aggregation-induced emission (AIE) have emerged as fascinating candidates for sensing multiple analytes. We report, synthesis of novel AIE active cyanostilbenes bearing benzimidazole moiety at one end and a phenyl group bearing electron-donating amino groups at the other terminal. The compounds show excellent AIE emission in aqueous media, and the addition of picric acid results in emission quenching accompanied by sharp color demarcation. Compounds also show strong selectivity for picric acid compared to other nitroaromatic and phenolic substrates with a ppm level of detection. The mechanistic details of the sensing mechanism were elucidated using H-1 NMR measurements that reveal the H-bonding interaction of picric acid with the fluorophores. The results demonstrate that these novel benzimidazole-fluorophores could be potential candidates for the selective and sensitive detection of picric acid.