Imidazo[1,5-α]pyridine-based fluorescent probe with a large Stokes shift for specific recognition of sulfite

By taking advantage of the intramolecular charge transfer (ICT) process, we presented a novel fluorescent probe IPY-SO₂ based on imidazo[1,5-α]pyridine derivative for detecting SO₃^2- with a low detection limit (70 nM). Combining its favorable turn-on fluorescence feature (75-fold), rapid response (5 min), high selectivity, large Stokes shift (174 nm) and low cytotoxicity, IPY-SO₂ was successfully applied to imaging SO₃² in living MCF-7 cells and zebrafish.