A new series of dinuclear ruthenium(II) polypyridyl complexes, which possess larger π-conjugated systems, good water solubility and pH resistance, and high photostability, were developed to act as single and two-photon luminescence cellular imaging probes.

5Mitochondria dynamic processes are essential for mammalian development and engaged in several diseases. However, commercial mitochondrial probes are currently too limited to satisfactorily track these dynamics. In this present work, seven dinuclear iridium(III) complexes [(ppy) 2 Ir(L 1-7 )Ir(ppy) 2 ] 2+ (Ir1-Ir7, ppy = 2-phenylpyridine, L = 1,3-bis(1-substituted-1H-imidazo[4,5-f][1,10]phenanthroline-2-yl)benzene) were synthesized. Possessing high specificity to mitochondria, low cytotoxicity and high resistance to the 10 loss of mitochondrial membrane potential, Ir2-Ir7 can serve as mitochondrial imaging dyes. Ir3 and Ir6 are further developed to track the mitochondrial morphological changes during the early stages of apoptosis. In addition, the relationship of the electron drawing/withdrawing groups in these systems with the photophysical properties and photostability is also discussed. 65 to red. 18 Recently, Grazulevicius and co-workers reported the development of the "warm-white" OLEDs that based on the application of bifunctional molecules via attachment of carbazole-based fragments to the phosphorescent iridium(III) complexes core. The triplet excited state of these bimolecular 70 complex were confirmed by the DFT and (TD) DFT methods. [19][20] In addition to OLED, iridium(III) complexes have also been applied as sensors, 21-22 in vivo tumour imaging, 23-24 , live cell compartmentalization staining and so on. Huang, Li and Schubert have reviewed these fields. [25][26][27] It is interesting that various 75 iridium(III) complexes have been developed as cytoplasm, nucleus, nucleolus, Golgi apparatus, lysosomes and vacuoles imaging dyes, 28-31 reports on iridium(III) complexes as mitochondrial dyes are quite less, although cationic species are Graphical AbstractDinuclear iridium(III) complexes [(ppy) 2 Ir(L 1-7 )Ir(ppy) 2 ] 2+ (Ir1-Ir7) serve as mitochondrial imaging dyes, Ir3 and Ir6 are further developed to track the mitochondrial morphological changes during the early stages of apoptosis.