Dihydrogen Phosphate Anion-Templated Supramolecular Assembly with Bistable [3]Rotaxane: Application in Selective and Sensitive Picric Acid Detection

A bistable [3]rotaxane comprising [23]crown ether and a pyrene fluorophore selectively exhibited dramatic pyrene excimer emission in the presence of the dihydrogen phosphate anion due to the generation of a supramolecular assembly. The assembly was generated via hydrogen bonding between methyl triazolium moieties and the dihydrogen phosphate anion, bringing the pyrene moieties into proximity. The assembly could selectively detect picric acid over other nitroaromatics through excimer fluorescence quenching via energy transfer from the assembly and proton transfer from the picric acid. The quenching efficiency for picric acid is found to be 96%, with a limit of detection of 198 nM.