Colorimetric and fluorogenic signalling of fluoride ions by diketopyrrolopyrrole-based chemosensor

A new colorimetric and on-off fluorescence sensor based on diketopyrrolopyrrole (DPP) was synthesized for detection of fluoride anion. The sensor displayed a rapid responsivity and high selectivity and sensitivity towards F- over other anions, and it also exhibited a very low detection limit of 4.07 x 10(-8) M. The signaling process was confirmed by UV-vis, fluorescence measurements as well as H-1 and F-19 NMR spectroscopy. The experimental results revealed that the formation of anionic species from deprotonation of the hydrazone N-H moiety by fluoride ion was responsible for the spectral changes. Density function theory calculations were conducted to rationalize the optical response of the sensor.