نبذة مختصرة : International audience ; Iridium(III) complexes have been recognized as promising candidates for two-photon sensitized photodynamic therapy (PDT). In this context, we report on the study of two complexes, a monomer (IrL 1 ) and a dimer (Ir 2 L 2 ). Both complexes possess 2-phenylpyridine cyclometallating ligands and a pyridylbenzimidazole derivative as ancillary ligand. In the dimer, the two Ir(III) centers are connected by a non-conjugated bridged bis(pyridylbenzymidazole). We compare the photophysical properties of these complexes. Both display phosphorescent emission in the orange-red part of the visible spectrum, with emissions centered at 610 nm for IrL 1 and 625 nm for Ir 2 L 2 , both exhibiting quantum yields of ~24%. However, Ir 2 L 2 turns to be much brighter than the monomer making the dimer four times brighter than IrL 1 . This trend is consistent under two-photon excitation (TPE) and the singlet oxygen generation quantum yields, indeed the dimer displaying a figure of merit ( TPA x φ ∆ ) of 40, compared to only 5 for the monomer. Both complexes generate intracellular ROS and exhibit strong phototoxicity upon blue light activation (=420 nm), achieving sub-micromolar IC 50 values in HT29 and A549 cell lines after 24h of incubation. Moreover, with TPE (=800 nm), both complexes also generate intracellular ROS and induce cancer cell death.
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