A time-resolved near-infrared phosphorescent iridium(iii) complex for fast and highly specific peroxynitrite detection and bioimaging applications.

Peroxynitrite (ONOO-), one of the reactive oxygen/nitrogen species (ROS/RNS) found in vivo, plays crucial roles in many physiological and pathological processes. The ability to selectively and sensitively determine ONOO-in vivo is important for the understanding of its biological roles. Thus, by utilizing the excellent chemical stability and photostability, high luminescence efficiency, and long luminescence lifetime of iridium complexes, we developed a novel near-infrared (NIR) phosphorescent iridium(iii) complex (FNO2) probe to detect ONOO- within seconds. The probe FNO2 showed better selectivity towards ONOO- over other interfering biomolecules, including O2- and ClO-. Moreover, it possessed a long luminescence lifetime, which enabled successful elimination of the interference from background fluorescence in vitro (simulated by Rhodamine B) in time-resolved emission spectra. Finally, in addition to its low cytotoxicity, the probe FNO2 showed emission wavelength in the NIR region and was able to specifically sense ONOO- induced in living cells and inflamed mouse models.