A simple colorimetric and ON–OFF fluorescent chemosensor for biologically important anions based on amide moieties

A simple colorimetric and fluorescent anion chemosensor based on amide moieties, 6-nitro-1,4-dihydroquinoxaline-2,3-dione has been designed, synthesized and characterized by 1H NMR, ESI-MS and elemental analyses. The strong basic anions such as F− and AcO− resulted in significant decrease in fluorescent emission intensity of the compound 1, accompanied synchronously with a dramatic color change from colorless to deep yellow in organic medium. 1H NMR titration experiments shed light on the nature of the interactions between 1 and the anions.