Phosphorescent O2-Probes Based on Ir(III) Complexes for Bioimaging Applications

The design, synthesis, and investigation of new molecular oxygen probes for bioimaging, based on phosphorescent transition metal complexes are among the topical problems modern chemistry advanced bioimaging. Three iridium [Ir(N^C)2(N^N)]+ with cyclometallating 4-(pyridin-2-yl)-benzoic acid derivatives different di-imine chelate ligands have been synthesized characterized by mass spectrometry NMR spectroscopy. periphery these is decorated three relatively small “double-tail” oligo(ethylene glycol) fragments. All exhibit phosphorescence; their photophysical properties thoroughly studied, quantum chemical calculations were also performed. It turned out that changes in nature ligand greatly affected character electronic transitions responsible emission. Two this series show desired characteristics; they demonstrate appreciable yield (14–15% degassed aqueous solutions) a strong response to concentration, ca. three-fold increase emission intensity, an excited state lifetime upon deaeration solution. study model biological systems (buffer solutions containing fetal bovine serum—FBS) cytotoxicity assays (MTT) showed satisfy requirements application bioimaging experiments. was found internalized into cultured cancer cells localized mainly mitochondria lysosomes. Phosphorescent imaging (PLIM) experiments under hypoxic conditions cells, 1.5-fold excitation observed compared aerated suggesting applicability analysis hypoxia objects.