Benzothiazole possessing reversible and reusable selective chemosensor for fluoride detection based on inhibition of excited state intramolecular proton transfer

Abstract

A series of three benzothiazole derivatives BTBAs based on aryl amide groups have been developed, whose photophysical properties were remarkably changed by the presence of –OCH3 and –NO2 groups at para-position of aryl amides. Among these chemosensors, BTBA-OCH3 showed fluoride selectivity in its absorbance and emission behavior among the various interfering anions, along with conspicuous color change from colorless to yellowish green color. Substantially red shifted absorption as well as fluorescence band of BTBA-OCH3 in DMSO, was observed upon addition of F− ions. Inhibition of Excited State Intramolecular Proton Transfer (ESIPT) in sensor-anion deprotonated complex was suggested to be the signaling mechanism. 1H NMR titrations of the sensor with F− ions also supported deprotonation process. In particular, the spectral responses of this chemosensor could be tuned from side to side alternatively by adding F− and HSO4− anions in DMSO solvent.