Three new lanthanide heterocyclic beta-diketonate complexes [Dy(PPI)(3)(EtOH)(2)] (1), [Dy(PPI)(3)(DPEPO)] (2), and [Tb(PPI)(3)(DPEPO)] (3) [where HPPI = 3-pheny1-4-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 Ln(III) ion is coordinated to eight oxygen atoms that are provided by three bidentate beta-diketonate ligands and ethanol or bidentate DPEPO in a distorted square antiprismatic geometry. These complexes have high molar absorption coefficients (up to 3 X 10(4) M-1 cm(-1) at 285 nm) and display strong visible and, for Dy-III, 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 us for 1, 12 +/- 2% and 33 +/- 1 mu s for 2, and 42 +/- 6% and 795 +/- 1 mu s for 3. Moreover, the crystals of 2 and 3 exhibit brilliant triboluminescence, visible in daylight.