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

Abstract A novel fluorenone derived Schiff base chemosensor ( 1) has been synthesized as a colorimetric sensor for fluoride (F − ) ions in CH 3 CN 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 1 H 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.