4-methyl-7-[4-nitro-2-(trifluoromethyl)phenoxy]chromen-2-one

4-Methyl-7-(4-nitro-2-(trifluoromethyl)phenoxy)-2H-chromen-2-one is a turn-on fluorescent probe for the detection of hydrogen sulfide (H₂S). It can be excited at 348 nm in DMSO and fluorescence intensity increases in the presence of bisulfide (HS^-). 4-Methyl-7-(4-nitro-2-(trifluoromethyl)phenoxy)-2H-chromen-2-one is selective for HS^- over cysteine, AcO^-, F^-, H₂PO₄^-, Cl^-, Br^-, and I^- and is not cytotoxic up to a concentration of 150 μg/ml.