An ESIPT-active orange-emissive 2-(2′-hydroxyphenyl)imidazo[1,2-a]pyridine-derived chemodosimeter for turn-on detection of fluoride ions via desilylation

Abstract

Fluoride is an essential element for oral health with an optimum concentration of 0.7–1.2 ppm in drinking water, but it is detrimental at higher concentrations, causing fluorosis, acute gastric ulcer, urolithiasis, and kidney infection, which adds immense significance to its detection in water sources. In the current study, a new chemodosimeter (HIPS-Br) is designed by protecting a 2-(2′-hydroxyphenyl)imidazo[1,2-a]pyridine derivative (HIP-Br) with a fluoride recognizable tert-butyldiphenylsilane moiety and utilized for the selective detection of F⁻ ions by an excited-state intramolecular proton transfer (ESIPT)-based fluorimetric response. The probe HIPS-Br exhibits blue fluorescence in solution, and upon the incremental addition of F⁻ ions, it exhibits a turn-on response, exhibiting a strong orange emission at 598 nm by spontaneous cleavage of the tert-butyldiphenylsilane group to release fluorescent HIP-Br in the working solution. HIPS-Br displayed no or insignificant response towards numerous common anions, cations and small molecules, affirming its selectivity to F⁻ ions and offered a low limit of detection (LOD) of 1.2 ppb (6.6 × 10⁻⁸ M). The real sample analysis by spiking fluorides in water and toothpaste samples showed excellent percent recoveries. The chemodosimeter was successfully utilized in the solid-phase detection of F⁻ ions on silica-coated TLC plates and analyzed by ImageJ analysis, marking its utility in on-site quantitation purposes.