Urea/Thiourea based optical sensors for toxic analytes: A convenient path for detection of first nerve agent (Tabun)

Abstract

In the realm of supramolecular chemistry, the development in synthetic receptors for harmful analytes has attracted substantial attention in recent decades due to the fact that a huge number of chemical and biological processes involve molecular recognition of these species. It is therefore important to develop methods/techniques for sensing such analytes. To design and develop a chemical sensor, one or more urea/thiourea fragments are incorporated in acyclic, cyclic, or polymeric frameworks that are directly attached to the signaling units as well as spacers. Being a good hydrogen bond donor, urea/ thiourea has an excellent binding affinity for anionic and neutral species. In our research, we designed and developed urea/ thiourea based novel receptors decorated with finely tuned signaling units and spacers for the detection of fluoride, cyanide, and tabun (first nerve agent). The developed chromogenic and fluorogenic hosts instantaneously detect these toxic anions and analytes with exceptional selectivity over other interfering agents. Inspired by the multianalyte detection approach, we further aimed to explore novel chromo-fluorogenic receptors that not only detect these analytes but also differentiate from one another. Urea/thiourea motifs have been extensively used in the chemosensing of anionic and neutral analytes, supramolecular catalysis, and supramolecular medicinal chemistry. In this Account, these studies have also been briefly summarized.