Fluoride anions triggered “OFF–ON” fluorescent sensor for hydrogen sulfate anions based on a BODIPY scaffold that works as a molecular keypad lock

A BODIPY-based derivative 1 containing hydrazone moiety has been developed as a colorimetric and fluorometric sensor for fluoride and hydrogen sulfate anions. The UV–vis absorption, fluorescent emission and partial 1H NMR titrations experiments have been employed to study the sensing process. Sensor 1 could act as an efficient “On–Off” fluorescent sensor for fluoride anions based on the deprotonation process. In the presence of fluoride anions, sensor 1 could act as an “Off–On” fluorescent sensor for hydrogen sulfate anions based on the reversible protonation process. Sensor 1 could also behave as a molecular keypad lock with sequential chemical inputs of F− and HSO4− ions.