Phosphorescent iridium(III) complexes as multicolour probes for imaging of hypochlorite ions in mitochondria

Mitochondria are one of the major sources of cellular reactive oxygen species (ROS) and the hypochlorite ion (ClO-) is one kind of highly ROS involved in many important biological events. Herein, we present a novel class of mitochondrial ClO- probes. A series of iridium(III) complexes, Ir1-Ir4, were synthesized which exhibited a highly specific response of their phosphorescence signal toward ClO- over other ROS. By changing the cyclometalated ligands, the turn-on phosphorescent emission colours can be tuned from green to red. ICP-MS results and Mito-tracker co-staining experiments revealed that Ir1-Ir4 localized specifically in mitochondria. Finally, complexes Ir1-Ir4 were successfully applied in subcellular imaging for detection of endogenous ClO- in mitochondria.