Fluorescent "turn-Off" detection of fluoride and cyanide ions using zwitterionic spirocyclic meisenheimer compounds

Abstract

Stable zwitterionic spirocyclic Meisenheimer compounds were synthesized using a one-step reaction between picric acid and diisopropyl (ZW1) or dicyclohexyl (ZW3) carbodiimide. A solution of these compounds displays intense orange fluorescence upon UV or visible light excitation, which can be quenched or "turned-off" by adding a mole equivalent amount of F- or CN-ions in acetonitrile.Fluorescence is not quenched in the presence of other ions such as Cl-, Br-, I-, NO2-, NO3-, or H2PO4- These compounds can therefore be utilized as practical colorimetric and fluorescent probes for monitoring the presence of F- or CN- anions.