Novel colorimetric anion sensors based on N-acetylglyoxylic amides containing nitrophenyl signalling units

• We designed and synthesized N-acetylglyoxylic amide-based colorimetric anion sensors.
• Sensors 4 and 5 showed obvious color changes upon addition of CN− and F−.
• CN− and F− formed hydrogen bonds with the receptors and induced subsequent deprotonation.

N-acetylglyoxylic amides 4 and 5 bearing pendant 4-nitrophenyl and 2,4-dinitrophenyl groups respectively were synthesized and evaluated as anion sensors. A crystal structure of 4 was obtained by X-ray crystallography. Compounds 4 and 5 behaved as colorimetric sensors for CN− and F−, and exhibited naked eye-detectable color changes upon the addition of these anions. The chromogenic properties of 4 and 5 were assessed by UV–Vis and 1H NMR spectroscopy.

N-acetylglyoxylic amides based anion colorimetric sensors 4 and 5 demonstrated recognition of CN− and F−via hydrogen bonds and subsequent NH deprotonation which led to the intramolecular charge-transfer resulting in visible color changes.Figure optionsDownload as PowerPoint slide