Perdeuterated 2,2′-Bipyridine-6,6′-dicarboxylate: An Extremely Efficient Sensitizer for Thulium Luminescence in Solution

Lanthanoid
luminescence has become an important pillar for many modern photonics
applications such as bioanalytical research or functional material
science. So far, however, thulium despite having one of the most interesting
photophysics among the lanthanoids has suffered from extremely low
luminescence efficiencies in molecular complexes with organic sensitizer
ligands. This has greatly hampered the investigation and application
of thulium emission in solution. Here, the discovery of a powerful
sensitizer for thulium photoluminescence is reported. The corresponding
thulium complex exhibits emission efficiencies (quantum yield Φ
> 0.12%; lifetime τobs = 4.6 μs; brightness
εΦ > 30 M–1 cm–1) and can even be detected at low micromolar concentrations in high-phonon
solvents like water without the need for laser excitation.