4-Methyl-7-(2-nitrophenoxy)-2H-chromen-2-one

4-Methyl-7-(2-nitrophenoxy)-2H-chromen-2-one (compound 2f) is a selenol fluorescent probe designed based on a nucleophilic aromatic substitution mechanism. It can selectively recognize selenols in neutral aqueous solution without significant interference from biological thiols, amines or alcohols. It can be used to quantify the selenium content in selenoenzymes and to image the activity of endogenous selenols in living cells.