Dinuclear iridium( iii ) complexes as phosphorescent trackers to monitor mitochondrial dynamics

(Ir1-Ir7, ppy = 2-phenylpyridine, L = 1,3-bis(1-substituted-imidazo[4,5-f][1,10]phenanthroline-2-yl)benzene) were synthesized. Possessing a high specificity for mitochondria, low cytotoxicity and high resistance to the loss of the mitochondrial membrane potential, Ir2-Ir7 can serve as mitochondrial imaging dyes. Ir3 and Ir6 are further developed for tracking mitochondrial morphological changes during the early stages of apoptosis. In addition, the relationship of the electron donating/withdrawing groups in these systems with the photophysical properties and photostability is also discussed.