A new D–π–A type intramolecular charge transfer Dyad System to detect F−: Anion induced CO2 sensing

Abstract

A new D–π–A type intramolecular charge transfer (ICT) based fluorescence probe have been designed and synthesized by appending imidazole (donor, D) and benzothiazole (acceptor, A) moieties through a thiophene bridge. The molecular probe upon interaction with different class of anions showed fluorescence turn-on behavior to detect fluoride anion (F−) selectively, in acetonitrile. Job’s plot analysis revealed a 1:1 binding stoichiometry between probe and F− with high binding constant and detection sensitivity (51nM; 0.092 ppb). Moreover, upon interaction of 1+F− with CO2 the original chromo and fluorogenic behavior of the probe was revived. The change in photophysical behavior and NMR spectroscopic studies suggested about the “On-Off-On” type of fluorescence sensing mechanism, involving deprotonation of −NH fragment of imidazolyl unit in the presence of F−.