EuroTracker dyes: highly emissive europium complexes as alternative organelle stains for live cell imaging

Nine very bright europium(III) complexes with different macrocyclic ligands have been prepared that exhibit excellent cell uptake behaviour and distinctive sub-cellular localisation profiles, allowing the use of fluorescence microscopy and time-gated spectral imaging to track their fate in cellulo. Their use as cellular imaging stains is described for the selective illumination of mitochondria, lysosomes or the endoplasmic reticulum of various mammalian cell types.