Thermally-assisted photosensitized emission in a trivalent terbium complex
Yuichi Kitagawa, Kaori Shima, Takuma Nakai, Marina Kumagai, Shun Omagari, Pedro Paulo Ferreira da Rosa, S. Shoji, Koji Fushimi, Yasuchika Hasegawa
Abstract
Abstract 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%).