Quinoxaline-imidazolium receptors for unique sensing of pyrophosphate and acetate by charge transfer

Quinoxaline derivatives (1-4) bearing two imidazolium moieties are found to strongly bind anions and show unique charge-transfer fluorescent responses to pyrophosphate and acetate, whereas they show excimer formation with other anions. Anion-binding studies are investigated with fluorescence and H-1 NMR analysis, single-crystal X-ray analysis, and theoretical calculations.