Near-Infrared Luminescent Osmium(II) Complexes with an Intrinsic RNA-Targeting Capability for Nucleolus Imaging in Living Cells.

Os(II) polypyridyl complexes usually display an excellent NIR (near-infrared) emission, which conforms to the optical window in a biological system. At the moment, there is only one commercial RNA dye, SYTO RNA-Select, which emits green fluorescence and only stains RNA in the fixed cells. Therefore, it is necessary to study NIR-emitting RNA probes in the live cells. Here, we study two novel osmium complexes with NIR luminescence for cell imaging and find the specific binding ability of these two osmium complexes with RNA. The osmium(II) complexes can selectively light up RNA and enable NIR luminescent imaging of RNA of the nucleus of the live cells. It is the first example of osmium complexes in application of RNA-specific luminescence imaging. This work suggests that RNA might be a novel target of osmium complexes.