A New Reversible Colorimetric Chemosensor Based on Julolidine Moiety for Detecting F⁻

We synthesized an original reversible colorimetric chemosensor PDJ ((E)-9-((2-(6-chloropyridazin-3-yl)hydrazono)methyl)-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-8-ol) for the detection of F⁻. PDJ displayed a selective colorimetric detection to F⁻ with a variation of color from colorless to yellow. Limit of detection of PDJ for F⁻ was calculated as 12.1 µM. The binding mode of PDJ and F⁻ turned out to be a 1:1 ratio using Job plot. Sensing process of F⁻ by PDJ was demonstrated by ¹H NMR titration and DFT calculation studies that suggested hydrogen bond interactions followed by deprotonation. Moreover, the practicality of PDJ was demonstrated via a reversible test with TFA (trifluoroacetic acid).