Thermally-assisted photosensitized emission in a trivalent terbium complex.

Luminescent lanthanide complexes containing effective photosensitizers are promising materials for use in displays and sensors. The photosensitizer design strategy has been studied for developing the lanthanide-based luminophores. Herein, we demonstrate a photosensitizer design using dinuclear luminescent lanthanide complex, which exhibits thermally-assisted photosensitized emission. The lanthanide complex comprised Tb(III) ions, six tetramethylheptanedionates, and phosphine oxide bridge containing a phenanthrene frameworks. The phenanthrene ligand and Tb(III) ions are the energy donor (photosensitizer) and acceptor (emission center) parts, respectively. The energy-donating level of the ligand (lowest excited triplet (T 1 ) level = 19,850 cm -1 ) is lower than the emitting level of the Tb(III) ion ( 5 D 4 level = 20,500 cm -1 ). The long-lived T 1 state of the energy-donating ligands promoted an efficient thermally-assisted photosensitized emission of the Tb(III) acceptor ( 5 D 4 level), resulting in a pure-green colored emission with a high photosensitized emission quantum yield (73%).