Density functional theory investigation of Eu(III) complexes with beta-diketonates and phosphine oxides: model complexes of fluorescence compounds for ultraviolet LED devices.
ABSTRACT The density functional theory was employed to investigate Eu(III) complexes with three beta-diketonates and two phosphine oxides (complex M1: Eu(bdk)3(TPPO)2, complex M2: Eu(bdk)3(TMPO)2, and complex M3: Eu(bdk)3(TPPO)(TMPO)) deemed to be the model complexes of the fluorescence compounds for the ultraviolet LED devices we have recently developed. For each complex, two minimum energy points corresponding to two different optimized geometries (structures A and B) have been found, and the difference of the energy between two minimum energy points is found to be quite small (less than 1 kcal/mol). Vertical excitation energies and oscillator strengths for each complex at two optimized geometries have been obtained by the time-dependent density functional theory, and the character of the excited states has been investigated. For complex M3, the absorption edge is red-shifted, and the oscillator strengths are relatively large. The efficiency of intersystem crossing and energy transfer from the triplet excited state to the Eu(III) ion is considered by calculating DeltaE(ISC) (the energy difference between the first singlet excited state and the first triplet excited state) and DeltaE(ET) (the difference between the excitation energy of the complex for the first triplet excited state and the emission energy of the Eu(III) ion for 5D to 7F).
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ABSTRACT: The paper proposes novel molecular designs for rare-earth complexes involving the introduction of two different phosphine oxide structures into one rare-earth ion. These designs are effective for improving solubility and emission intensity. Additionally, the complexes are indispensable for realizing high performances in LEDs and security media. The thermodynamic properties of Eu(III) complexes are correlated with the solubility. Correlations between coordination structures and emission intensity were explained by NMR analysis. The luminous flux of red LED devices with Eu(III) complexes is very high (20 mA, 870 m lumen). A new white LED has its largest spectra intensity in the red region and a human look much more vividly under this light.Materials. 01/2010;
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ABSTRACT: 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.Dalton Transactions 10/2010; 39(38):8919-24. · 3.81 Impact Factor
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ABSTRACT: A novel class of efficient visible light sensitized antenna complexes of Eu 3+ based on the use of a highly conjugated b-diketonate, namely, 1-(4-biphenoyl)-3-(2-fluoroyl)propanedione (HBFPD) and 1,10-phenanthroline as an ancillary ligand has been designed, synthesized, characterized and their photophysical properties (PL) investigated. PL measurement results indicated that suitably expanded p-conjugation in the complex molecules makes the excitation band red shift to the visible region and hence the Eu 3+ complexes exhibit intense red emission under blue light excitation (440 nm) with a solid-state quantum yield of 32 AE 3%, which is the highest so far reported in the literature. Further, in the present work, the visible sensitized Eu 3+ complex has been covalently anchored to the ordered mesoporous MCM-41 via the modified HBFPD ligand for the first time to the best of our knowledge. b-Diketonate grafted to the coupling agent 3-(triethoxysilyl)propylisocyanate was used as the precursor for the preparation of mesoporous nanomaterials. MCM-41 consisting of ternary complex Eu(SiBFPD) 3 (phen) covalently bonded to the silica-based network, which was designated as Eu(SiBFPD) 3 (Phen)/MCM-41 (3), was obtained by interacting europium nitrate, SiBFPD-Na and 1,10-phenanthroline into the hybrid material via a ligand-exchange reaction. The designed material was further characterized by powder X-ray diffraction, dynamic light scattering (DLS) technique, thermogravimetric analysis, N 2 adsorption-desorption, SEM, TEM, FT-IR, FT-Raman, 13 C and 29 Si CPMAS NMR and photoluminescence spectroscopic techniques. The hybrid material covalently bonded to MCM-41 exhibits an efficient intramolecular energy transfer process from the silylated b-diketonate to the central Eu 3+ , namely, the ''antenna effect'', which favored a stronger red/orange intensity ratio, longer lifetime, and high thermal stability than the precursor complex.Journal of Materials Chemistry 05/2010; · 5.97 Impact Factor