Highly efficient coumarin-derived colorimetric chemosensors for sensitive sensing of fluoride ions and their applications in logic circuits.

In this study, three new compounds 6-substituted-3-acetylcoumarin 4-(2'-isocamphanyl)thiosemicarbazones (3a, 3b, and 3c) were facilely synthesized and employed as colorimetric chemosensors for fluoride ions. The recognition behaviors of receptors 3a, 3b, and 3c toward F were investigated by using UV-vis absorption spectroscopy. Among them, the receptor 3c displayed more superior sensitivity and rapid response time toward F with a swift naked-eye color change from colorless to purple, and its detection limit was as low as 6.3 × 10 M, and the binding constant was calculated to be 2.58 × 10 M. Furthermore, the interaction mechanism between the receptor 3c and F was studied by H NMR, HRMS, and density functional theory (DFT) studies, suggesting that initial formation of a hydrogen-bonded host-guest complex and the subsequent deprotonation of receptor 3c upon the addition of excess F, which was responsible for the remarkable changes in the absorption spectra of 3c. Besides, a combinatorial logic circuit of IMPLICATION and INHIBITION gates at the molecular level was fabricated using the reversibility of receptor 3c toward F and Mg. Finally, the test strips coated with receptor 3c revealed a good sensitivity for F in an aqueous medium. Apart from that, the excellent performance of receptor 3c for detecting F was reconfirmed by grinding them with KBr powder.