Brilliant Photoluminescence and Triboluminescence from Ternary Complexes of Dy^III and Tb^III with 3‑Phenyl-4-propanoyl-5-isoxazolonate and a Bidentate Phosphine Oxide Coligand

Three new lanthanide heterocyclic β-diketonate complexes [Dy­(PPI)3(EtOH)2] (1), [Dy­(PPI)3(DPEPO)] (2), and [Tb­(PPI)3(DPEPO)] (3) [where HPPI = 3-phenyl-4-propanoyl-5-isoxazolone and DPEPO = bis­(2-(diphenylphosphino)­phenyl)­ether oxide] have been synthesized and fully characterized. Single-crystal X-ray diffraction analyses reveal that these complexes are mononuclear and that the central LnIII ion is coordinated to eight oxygen atoms that are provided by three bidentate β-diketonate ligands and ethanol or bidentate DPEPO in a distorted square antiprismatic geometry. These complexes have high molar absorption coefficients (up to 3 × 104 M–1 cm–1 at 285 nm) and display strong visible and, for DyIII, NIR luminescence upon irradiation at the ligand-centered band in the range 250–350 nm. The emission quantum yields and the luminescence lifetimes at room temperature are 3 ± 0.5% and 15 ± 1 μs for 1, 12 ± 2% and 33 ± 1 μs for 2, and 42 ± 6% and 795 ± 1 μs for 3. Moreover, the crystals of 2 and 3 exhibit brilliant triboluminescence, visible in daylight.