Aromatization of 9,10-Dihydroacridine Derivatives: Discovering a Highly Selective and Rapid-Responding Fluorescent...

As part of an effort to develop generally applicable strategies for creating probes suitable for detecting important molecular and ionic species, the oxidative aromatization of nonfluorescent 9,10-dihydroacridine derivatives triggered by peroxynitrite (ONOO^-) led to the identification of compound 2H, 9-phenyl-9,10-dihydroacridine-4-carboxylic acid, as a rapid-responding fluorescent probe capable of detecting ONOO^- with an extraordinary selectivity. Adding a little more than 1 equiv of ONOO^- to a solution of 2H resulted in over 100-fold fluorescence enhancement. In sharp contrast, treating 2H with excessive amounts of other oxidants that often interfere with the detection of ONOO^- failed to lead to noticeable fluorescence increase. The reaction of ONOO^- with 2H shows a similar efficiency in the pH range of 2-8. Low cytotoxicity was observed for 2H and its aromatized product. Bioimaging experiments revealed the promising potential of 2H as a new fluorescent probe for the selective detection of intracellular ONOO^-.