Colorimetric and fluorimetric detection of fluoride ion using thiazole derived receptor.

[Display omitted] • Thiazole-derived receptor with two fluoride binding sites i.e., urea and salicylaldimine moieties. • An efficient colorimetric and fluorimetric sensor for fluoride ions. • Low limit of detection (8.6 nM) with high sensitivity. • Preferential deprotonation of −OH proton of salicylaldimine moiety. Thiazole based receptor 3 , was designed and synthesized by condensation reaction of 5–chlorosalicylaldehyde with 4-(4-phenylthiazol-2-yl)semicarbazide for colorimetric and fluorimetric detection of fluoride ion. Receptor 3 was characterized by 1H NMR, 13C NMR, and HRMS, and shows absorption in 280–400 nm region with emission at 442 nm in tetrahydrofuran (THF). Addition of fluoride ion to the THF solution of receptor 3 results in color change from colorless to yellow with significant change in UV–Visible absorption. The receptor–anion interaction occurs via hydrogen bonding followed by deprotonation which results in large bathochromic shift in absorption spectra and naked-eye color change. The colorimetric changes show selective response for fluoride ions over other anions. Fluorescence studies exhibit remarkable enhancement in emission intensity upon addition of fluoride ion with a limit of detection (LOD) of 8.6 nM. The 1H NMR titration studies exhibit deprotonation of the –OH proton of the salicylaldimine moiety resulting significant colorimetric and fluorimetric changes. [ABSTRACT FROM AUTHOR]