Fluorescein and eosin as sensitizing chromophores in near-infrared luminescent ytterbium(III), neodymium(III) and erbium(III) chelates

Near-infrared luminescent ytterbium(III), neodymium(III) and erbium(III) chelates containing organic chromophores derived from fluorescein and eosin have been synthesized and studied spectroscopically. The complexes can be efficiently excited with visible light and show intense lanthanide luminescence at low concentrations (2≈ 10−6 mol l−1) in D2O as a result of energy transfer from the dye moiety to the rare earth ion. Quenching of the luminescence of the complexes by molecular oxygen reveals information on the rate of energy transfer from the “antenna” chromophore to the lanthanide ion.