A Mitochondria‐Targeted Fluorescent and Colorimetric Probe for Sulfur Dioxide Derivatives and Hydrogen Peroxide in Live Cells

The abnormal fluctuations of sulfur dioxide (SO 2 ) and its derivatives are closely associated with various physiological and pathological progresses in biological systems. Herein, we have developed two fluorescent and colorimetric probes based on a hemicyanine dye for the detection of SO 2 derivatives and hydrogen peroxide (H 2 O 2 ) in vitro and live cells. The response mechanisms involve an SO 2 ‐derivative‐mediated nucleophilic addition reaction to the double bond and subsequent H 2 O 2 ‐promoted elimination of bisulfite. As well as having excellent photophysical properties, the probe with higher fluorescence efficiency is further applied for live cell imaging, and it is found that it can solely accumulate in mitochondria and track SO 2 derivatives and H 2 O 2 in live cells.