Various fluorescence microscopy techniques require bright NIR-emitting fluorophores with high chemical and photostability. Now, the significant performance improvement of phosphorus-substituted rhodamine dyes (PORs) upon substitution at the 9-position with a 2,6-dimethoxyphenyl group is reported. The thus obtained dye PREX 710 was used to stain mitochondria in living cells, which allowed long-term and three-color imaging in the vis-NIR range. Moreover, the high fluorescence longevity of PREX 710 allows tracking a dye-labeled biomolecule by single-molecule microscopy under physiological conditions. Deep imaging of blood vessels in mice brain has also been achieved using the bright NIR-emitting PREX 710-dextran conjugate.

Various fluorescence microscopytechniques require bright NIR-emitting fluorophores with high chemical and photostability.Now,the significant performance improvement of phosphorus-substituted rhodamine dyes (PORs) upon substitution at the 9-position with a2 ,6-dimethoxyphenyl group is reported. The thus obtained dye PREX 710 was used to stain mitochondria in living cells,which allowed longterm and three-color imaging in the vis-NIR range.Moreover, the high fluorescence longevity of PREX 710 allows tracking ad ye-labeled biomolecule by single-molecule microscopy under physiological conditions.Deep imaging of blood vessels in mice brain has also been achieved using the bright NIRemitting PREX 710-dextran conjugate.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.