Biocompatible Phosphorescent O2 Sensors Based on Ir(III) Complexes for In Vivo Hypoxia Imaging

In this work, we obtained three new phosphorescent iridium complexes (Ir1–Ir3) of general stoichiometry [Ir(N^C)2(N^N)]Cl decorated with oligo(ethylene glycol) fragments to make them water-soluble and biocompatible, as well protect from aggregation biomolecules such albumin. The major photophysical characteristics these are determined by the nature two cyclometallating ligands (N^C) based on 2-pyridine-benzothiophene, since quantum chemical calculations revealed that electronic transitions responsible for excitation emission localized mainly at fragments. However, use various diimine (N^N) proved affect yield phosphorescence allowed changing complexes’ sensitivity oxygen, due variations in steric accessibility chromophore center O2 molecules. It was also found N^N made it possible tune biocompatibility resulting compounds. wavelengths Ir1–Ir3 maxima fell range 630–650 nm, yields reached 17% (Ir1) a deaerated solution, molecular estimated ratio lifetime aerated water solutions, displayed highest value, 8.2, Ir1. featured low toxicity, good solubility absence significant effect biological environment components parameters their emission. Of studied compounds, Ir1 Ir2 were chosen vitro vivo experiments estimate oxygen concentration cell lines tumors. These sensors have demonstrated effectiveness mapping distribution monitoring hypoxia objects studied.