Two novel carbazole-based beta-diketones with 2- or 2,7-substituted groups in the carbazole ring, 2-(4'4'4'-trifluoro-1'3'-dioxobutyl)-carbazole (2-TFDBC) and 2,7-bis(4'4'4'-trifluoro-1''3'-dioxobutyl)-carbazole (2,7-BTFDBC), and their europium(III) ternary complexes Eu(2-TFDBC)(3)phen and Eu(2)(2,7-BTFDBC)(3)(phen)(2) were synthesized via a dexterously designed routine, where phen is 1,10-phenanthroline. The Eu(III) complexes were characterized by elementary analysis, IR and UV-visible absorption spectroscopy, thermogravimetric analysis (TGA), and photoluminescence (PL) measurements. TGA shows that the decomposition temperatures of the complexes are 361.4 and 367.3 degrees C, respectively. PL measurement results indicated that suitably expanded pi-conjugation in the complex molecules makes the excitation band redshift to the visible region, and both the Eu(III) complexes exhibit intense red emission under blue-light excitation. The triplet state energy levels of 2-TFDBC and 2,7-BTFDBC in the complexes are higher than that of the lowest excited level of Eu(3+) ion, (5)D(0), so the photoluminescence mechanism of the Eu(III) complexes was proposed as a ligand-sensitized luminescence process. All of the results indicate that Eu(2-TFDBC)(3)phen and Eu(2)(2,7-BTFDBC)(3)(phen)(2) are promising candidates as visible-light excitable red phosphor for luminescence applications.

A novel 2-positional linked carbazole based β-diketone with methoxyl in the 7-position (EMOCTFBD), and its europium(III) ternary complex Eu(EMOCTFBD)(3)phen were synthesized via a dexterously designed indirect routine, where EMOCTFBD was 1-(9-ethyl-7-methoxyl-9H-carbazol-2-yl)-4,4,4-trifluorobutane-1,3-dione and phen was 1,10-phenanthroline. Eu(EMOCTFBD)(3)phen shows high thermal stability. The introduction of a methoxyl in the 7-position of the carbazole ring remarkably enhanced the excitation band intensity in the blue region, and the complex exhibited intense red emission under blue-light excitation. The lowest triplet state energy was measured and suggests the photoluminescence process as a ligand-sensitized luminescence process (antenna effect). A bright red-emitting diode was fabricated by coating the complex phosphor onto a ∼460 nm-emitting InGaN chip. All the results indicate that Eu(EMOCTFBD)(3)phen is an interesting red-emitting material excited by blue light, and therefore may be applied in many fields without UV radiation.

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