Fluorenone Appended Colorimetric Sensor for Cascade Detection of Fluoride and Calcium Gluconate with Applications in Solid State and Logic Gate Systems

A novel fluorenone derived Schiff base chemosensor (1) has been synthesized as a colorimetric sensor for fluoride (F-) ions in CH3CN and characterized by various analytical techniques. The chemosensor 1 perceived high selectivity for F- ion detection in the presence of other anions along with naked eye color change from yellow to orange-red with quantitative detection limit of 900 nM. The UV-vis changes, density functional theoretical (DFT) calculations and H-1 NMR titration studies pointed to F- ion induced deprotonation of -OH of sensor 1 that has been proposed to be responsible for the observed absorption as well as color changes. The sensor 1 has also been efficiently applied for the solid state concentration dependent naked eye detection of F- ions in the form of filter paper strips and smartphone applications. The in-situ generated 1-F- complex was further utilized for cascade recognition of calcium gluconate (CG). The reversible and reproducible changes produced by the addition of F- ions and CG enabled 1 to be used as "INHIBIT" molecular logic system and "SET/RESET" memorized device at the molecular level.