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.