RESUMO
Singlet oxygen (1O2), as a highly reactive oxygen species, plays an important role in the physical, chemical and biomedical fields, especially during photodynamic therapy (PDT) process. In this work, two iridium(III) complexes containing an anthracene unit in their diimine ligand were designed and synthesized to monitor 1O2 in living cells. The complexes were weakly emissive owing to the photoinduced electron transfer process, but exhibited intense luminescence upon capturing 1O2, resulting from the formation of the corresponding endoperoxide analogues. The remarkable turn-on luminescence response was specific toward 1O2 and in preference to other reactive oxygen species. The utilization of one of the complexes for imaging 1O2 in living cells has also been demonstrated using three different cells lines. Cells incubated with the complexes were hardly emissive. Further light irradiation at 475 nm triggered intracellular emission turn on, indicative of the production of 1O2 photochemically. The emissive pattern was well colocalized with commercially available MitoTracker, suggesting the potential applications of the complexes for imaging mitochondria 1O2. The 1O2 capturing properties rendered the complexes low photocytotoxicity since 1O2-caused oxidative damage toward cellular molecules and structures was inhibited.