Click-Derived 1,4-Disubstituted 1,2,3-Triazoles as Efficient Fluorogenic Chemosensors: Harnessing CuAAC for Anion Recognition

Abstract This work explores the design, synthesis, and analytical investigations of novel fluorogenic chemosensors based on the 1,2,3-triazole moiety engineered to respond selectively to fluoride and cyanide anions. The rationale for selecting the triazole-based receptor lies on the ability of 1,2,3-triazoles to recognize anions through their polarized Csp2−H proton, together with an ortho-substituted phenolic-OH group through a cooperative mechanism. The ortho-substituted phenolic-OH provides receptor preorganization as well as an acidic hydrogen, facilitating analyte-induced deprotonation by a basic anion. The resulting phenoxide is stabilized by conjugative delocalization, producing a pronounced UV−visible response toward F− and CN−. The sensing behavior has been evaluated in DMSO using both UV−visible absorption and fluorescence emission spectroscopy. The appearance of a new absorption peak along with the original absorption peak of the sensor as well as quenching of the emission peak upon addition of the analyte to the sensor significantly implies successful recognition. Key performance metrics, such as binding affinities of 4.09 × 103 M−1 for CN− with phenyl 2-((1-(2-hydroxyphenyl)-1H-1,2,3-triazol-4-yl)methoxy)benzoate (3aa), stoichiometric ratios, as well as detection limits of 17.2 μM for CN− with 3aa have been evaluated with the help of UV−visible absorption spectroscopy and have been performed for all the receptor molecules. To demonstrate practical utility, the chemosensor was successfully employed to detect cyanide in sprouted potatoes quantitatively. Further, a DFT study has also been conducted which successfully validates the proposed sensing mechanism.