Europium Tris Research Articles

Chiroptical Study of Chiral Discrimination by Amino Acid Based Ionic Liquids

The chiral discrimination ability of amino acid based chiral ionic liquids is studied using chiroptical luminescence techniques. A racemic mixture of dissymmetric europium tris(2,6-pyridinedicarboxylate) complexes are dissolved in five chiral ionic liquids, including l- and d-alanine methyl ester bis(trifluoromethanesulfonimide), l-leucine methyl ester bis(trifluoromethanesulfonimide), l-proline methyl ester bis(trifluoromethanesulfonimide), and tetrabutylammonium l-alanate. Circularly polarized luminescence spectra are measured for the samples over the 283-323 K temperature range. Analysis of the spectroscopic results shows that the amino acid methyl ester chiral ionic liquids show discrimination with a preference (handedness) that corresponds to the stereoisomer (l- vs d-). Most of the chiral ionic liquids show enthalpically dominated discrimination, but l-leucine methyl ester bis(trifluoromethanesulfonimide) shows entropically dominated chiral discrimination.

“ON–OFF” switching of europium complex luminescence coupled with a ligand redox process

A triarylamine-functionalized terpyridine ligand formed a highly coordinated complex with europium tris(β-diketonate), which displayed reversible ''ON-OFF'' luminescence switching coupled with a ligand redox process of triarylamine/triarylaminium cations.

Enhancement of Light Emission from an Europium(III) Complex Based-OLED by Using Layer-By-Layer Assembled Hole-Transport Films

Rare earth complexes hold a promising future in light-emitting devices owing to their strong and sharp luminescence with very high quantum efficiency. Here we report an effective yet very simple way to study and eventually enhance the optoelectronic performance of an organic light emitting device (OLED) based on europium(III) tris(dibenzoylmethane) mono(1,10-phenanthroline), Eu(DBM)3Phen as an emitter. The approach is based on the layer-by-layer deposition of hole-transport films made of PANI/PEDOT:PSS bilayers onto the ITO anode, prior to the emissive layer. As a main advantage, the procedure ensures a great control of the hole-transport film thickness at nanometer level, and thus provides different interfacial conditions. Moreover, we have observed that the devicés current density and luminance are increased when PANI/PEDOT:PSS bilayers are applied. Such OLEDs emit purple color due to contributions from both Eu(III) and PVK emissions.

Luminescent solar concentrator employing rare earth complex with zero self-absorption loss

Luminescent solar concentrator (LSC) employing Eu(TTA)3(TPPO)2 (europium tris(2-thenoyl trifluoro acetonate)-di(triphenylphosphine oxide)) was fabricated in our work firstly, and then its current–voltage (I–V) performance under AM1.5G radiation with different radiation area were measured and compared with that of LSC employing dye. As there is no overlap between absorption spectrum and fluorescence spectrum of Eu(TTA)3(TPPO)2, it is found that the power conversion efficiency of LSC employing Eu(TTA)3(TPPO)2 decreases ten times slower than that of LSC employing dye reported with the increment of radiation area under AM1.5G. To accurately characterize the zero self-absorption loss of LSC employing rare earth complex more, external quantum efficiency (EQE) was also measured and simulated theoretically. When experiment data is compared with theoretical simulation, the measured EQE data at 380 nm is found to well coincide with theoretical result by taking host absorption loss into consideration. And the conclusion could be drawn that rare earth complex obviously shows zero self-absorption loss in use of LSC system and is proposed as a potential candidate for increasing the LSC efficiency. 2011 Elsevier Ltd. All rights reserved.

Enhancement of the Luminescence Efficiency of Europium(III) Tris(.BETA.-diketonato) Complex in Organic Media by Quaternary Ammonium Salts with Anionic Ligands

Benzyldimethyltetradecylammonium (BA14(+)) salts with anionic ligands (X(-)), such as bis(2-ethylhexyl)sulfosuccinate, bis(2-ethylhexyl)phosphate (BEHP(-)), and benzotriazole (BTA(-)) anions, were prepared. These salts were soluble in various organic solvents. The luminescence emission spectra of organic solutions of a red luminescent, tris(1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octadionato)europium(III) complex in the presence of the BA14X's were recorded. The emission intensity of the Eu(III) complex was increased remarkably by the addition of BA14X (X(-) = BEHP(-) and BTA(-)). This effect can be attributed to the formation of 1:1 X(-)-adducts of the Eu(III) complex, in which the asymmetry of the ligand field is increased so as to enhance the emission efficiency of the (5)D(0)→(5)F(2) transition. The enhancement effect by BA14X was higher than that of charge-neutral ligands, such as tri-n-octylphosphine oxide and 1,10-phenanthroline, which have been used as second ligands to enhance the emission efficiency of tris(β-diketonato)europium(III) complexes.

Synthesis of europium(III) phenanthroline-β-diketonate silicon-containing complex. Photoluminescence in solution and in sol-gel film

A phenanthroline benzoyltrifluoroacetonate europium complex showing a bright red photoluminescence at a wavelength 616 nm was synthesized by reacting 3-isocyanatopropyltriethoxysilane with anhydrous europium(III) tris(benzoyltrifluoroacetonate) and then with phenanthroline.

Spectral and optical properties of high-optical-quality organic glasses under prolonged ultraviolet irradiation

The effect of prolonged UV irradiation on optical and spectral luminescent properties of two types of high-quality optical organic glasses are studied by electronic absorption spectroscopy, spectrofluorimetry, IR spectroscopy, and atomic force microscopy. Glasses 2.3 mm in thickness are obtained through the layer-by-layer photopolymerization of an oligo(epoxy diacrylate) mixture with benzyl methacrylate and oligo(carbonate dimethacrylate). After the addition of europium tris(benzoyltrifluoroacetonate) to the photopolymerizing compositions, glasses that luminesce in the red spectral region are produced. The action of light gives rise to a slow photodecomposition of the luminescent component and causes a decline in the intensity of the band due to 5D0 → 7F2 transition of the europium cation. The growth of absorption in the yellow-green spectral region favors formation of an internal light filter; as a result, the photodecomposition of the europium complex in deep layers proceeds at a smaller rate than that in surface layers. IR-spectroscopy measurements demonstrate the accumulation of hydroxyl groups in oligo(carbonate dimethacrylate) films during irradiation in air. In an inert atmosphere, practically no photodegradation products are evolved from the matrix material.

Europium Complexes of a Novel Ethylenedioxythiophene-Derivatized Bis(pyrazolyl)pyridine Ligand Exhibiting Efficient Lanthanide Sensitization

A new class of highly luminescent nine-coordinated europium(III) tris(beta-diketonate) bis[(ethylenedioxythiophene)pyrazolyl]pyridine (L) complexes has been synthesized and the photophysical properties studied: 1 = Eu(hfac)(3)(L); 2 = Eu(tta)(3)(L); 3 = Eu(btfac)(3)(L). The solid-state structure of complex 1 has been determined by single-crystal X-ray crystallography and shows the geometry of the local coordination environment around the Eu(III) ion to be a slightly distorted tricapped trigonal prism. Luminescence lifetimes were found to be 581, 473, and 576 micros for complexes 1-3, respectively. Absolute quantum yields for complexes 1-3 were measured as 16.4 +/- 1.4%, 27.5 +/- 1.2%, and 22.2% +/- 0.3%, respectively.

ホスフィンオキシドを有するシルセスキオキサンとユーロピウム錯体との配位型ハイブリッドの作製

A phosphorescent coordination hybrid has been successfully prepared from silsesquioxane containing phosphine oxide and europium tris β-diketonate. The novel silsesquioxane was synthesized by the sol-gel reaction of corresponding trialkoxysilane obtained by the ene-thiol reaction of allyldipenylphosphine oxide and mercaptopropyltriethoxysilane. Despite the high concentration of the europium complex (50 wt%), the complex was dispersed completely into the silsesquioxane, giving a dense, homogeneous, and transparent hybrid thin film. The luminescence property of this film was also investigated. This hybrid thin film with the embedded europium complex shows bright phosphorescence accompanied with a characteristic sharp spectrum derived from the f-f transition of europium at ambient temperature. It can be concluded that the enhancement of the emission intensity and the branching ratio for the europium complex in the hybrid compared to the europium complex in PMMA is due to the formation of a coordination bond between the europium complex and the phosphine oxide in silsesquioxane.

Synthesis of C-functionalized acetylacetone and its europium complex. Preparation and study of luminescence of europium-containing sol-gel films

New fuctionalized ligand 3-(3′-triethoxysilylpropylaminocarbonyl)pent-2-on-3-en-4-ol (EtO)3SiCH2·CH2CH2NHC(O)-C[C(O)CH3][=C(OH)CH3] (I) containing ketoenol and triethoxysilyl groups is synthesized from 3-triethoxysilylpropyl isocyanate (EtO)3SiCH2CH2CH2N=C=O and acetylacetone. The reaction is accompanied by the formation of 2-(3′-triethoxysilylpropylaminocarboxy)-pent-2-en-4-one (EtO)3SiCH2CH2·CH2NHC(O)-OC(CH3)=CH-C(O)CH3 (II), the product of addition of acetylacetone enol form to isocyanate group. The ratio of amide I and urethane II forms is 7:3. Europium(III) tris[3-(3′-triethoxysilylpropylaminocarbonyl) pent-2-on-3-en-4-olate] is prepared from I and Eu(i-OPr)3. An alternative pathway consists in the reaction of europium tris(acetylacetonate) with 3-triethoxysilylpropyl isocyanate. Conditions of formation of transparent europium-containing sol-gel films were developed. Thermal stability and photoluminescence of the films were investigated.

Electrochemical behavior of europium (III) in N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide

N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPyNTf 2) was synthesized and characterized by CHNS elemental analysis, 1H and 13C NMR and IR spectroscopy. Europium tris[bis(trifluoromethylsulfonyl)imide] (Eu(NTf 2) 3) was prepared and studied for the electrochemical behavior of Eu(III) in BMPyNTf 2 at glassy carbon and stainless steel working electrodes at 298–373 K by cyclic voltammetry, chronopotentiometry and chronoamperometry. Cyclic voltammogram of Eu(III) in BMPyNTf 2 consisted of a quasi-reversible cathodic wave at −0.45 V (vs. Fc/Fc +, 373 K), which could be attributed to the reduction of Eu(III) to Eu(II) and an irreversible wave at −2.79 V (vs. Fc/Fc +) due to reduction of Eu(II) to Eu(0). The diffusion coefficient of Eu(III) in BMPyNTf 2 was determined to be in the range of ∼10 −7 cm 2 s −1 by various electrochemical methods and the charge transfer rate constant was determined to be ∼10 −5 cm s −1 by cyclic voltammetry.

The light-emitting and optical properties of high-optical-quality organic glasses doped with europium tris(benzoyltrifluoroacetonate)

Two types of transparent high-optical-quality organic glasses (rigid and flexible, 40 × 40 × 2.2 mm in size) containing 0.6–3.2 mass % europium tris(benzoyltrifluoroacetonate) (0.1–0.6 mass % of Eu) were obtained from photopolymerizing compositions using the technique of layer-by-layer photopolymerization. The glasses are characterized by a high level of light transmission (nearly 90%) within the range of 500–1100 nm. The photoluminescence (PL) spectra of samples which are not Eu-doped exhibit weak spectral bands in the region 350–600 nm. Doped glasses show intensive europium(III) cation PL: 538 nm (5D1 → 7F1), 580 nm (5D0 → 7F0), 593 nm (5D0 → 7F1), 614 nm (5D0 → 7F2), 653 nm (5D0 → 7F3), and 703 nm (5D0 → 7F4); the transition (5D0 → 7F2) demonstrates the strongest emission. Glass properties were studied using atomic force microscopy (AFM), differential scanning calorimetry (DSC), and X-ray spectroscopy.

Application of a 1H δ‐resolved 2D NMR experiment to the visualization of enantiomers in chiral environment, using sample spatial encoding and selective echoes

We present the application of a 2D broadband homodecoupled proton NMR experiment to the visualization of enantiomers. In a chiral environment, the existence of diastereoisomeric intermolecular interactions can yield-generally slight-variations of proton chemical shifts from one enantiomer to another. We show that this approach, which relies on a spatial encoding of the NMR sample, is particularly well suited to the analysis of enantiomeric mixtures, since it allows, within one single 2D experiment, to detect subtle chemical shift differences between enantiomers, even in the presence of several couplings. This sequence, which uses semiselective radio-frequency (rf) pulses combined to a z-field gradient pulse, produces different selective echoes in various parts of the sample. The resulting homonuclear decoupling provides an original delta-resolved spectrum along the diagonal of the 2D map where it becomes possible to probe the chiral differentiation process through every proton site where the resulting variation in the chemical shift is detectable. We discuss the advantages and drawbacks of this approach, regarding other experiments which provide homodecoupled proton spectra. This methodology is applied to the observation of enantiomers of (1) ( +/- )2-methyl-isoborneol coordinated to europium (III) tris[3-(trifluoromethyl-hydroxymethylene)-(+)-camphorate] in isotropic solution, and (2) ( +/- )3-butyn-2-ol dissolved in a chiral liquid-crystal solvent, in order to show the robustness of this pulse sequence for a wide range of chiral samples.

Synthesis of a novel chelating ligand from pentane-2,4-dione and 3-aminopropyl[tris(trimethylsilyloxy)]silane. europium(III) and erbium(III) imino enolates

Acetylacetone reacts with 3-aminopropyl[tris(trimethylsilyloxy)]silane to give a mixture of the isomers 4-[3′-tris(trimethylsilyloxy)silylpropyl]iminopent-2-en-2-ol (90%) and 4-[3′-tris(trimethylsilyloxy)silylpropyl]aminopent-3-en-2-one (10%). According to 1H and 13C NMR data, both isomers exist in the cis-and trans-forms. Anhydrous europium(III) and erbium(III) tris{4-[3′-tris(trimethylsilyloxy)silylpropyl]iminopent-2-en-2-olates} were obtained from the mixture of the isomers and the corresponding propan-2-olates Eu(OPri)3 and Er(OPri)3. The resulting complexes are transparent air-stable liquids that are distillable in vacuo and well soluble in photopolymerizable polyorganosiloxane caoutchoucs and urethane acrylate oligomers. The volatility parameters of the europium(III) complex were studied.

A homogeneous resonance energy transfer-based assay to monitor MutS/DNA interactions

Probing the interactions of the DNA mismatch repair protein MutS with altered and damaged DNA is of great interest both for the understanding of the mismatch repair system function and for the development of tools to detect mutations. Here we describe a homogeneous time-resolved fluorescence (HTRF) assay to study the interactions of Escherichia coli MutS protein with various DNA substrates. First, we designed an indirect HTRF assay on a microtiter plate format and demonstrated its general applicability through the analysis of the interactions between MutS and mismatched DNA or DNA containing the most common lesion of the anticancer drug cisplatin. Then we directly labeled MutS with the long-lived fluorescent donor molecule europium tris–bipyridine cryptate ([TBP(Eu 3+)]) and demonstrated by electrophoretic mobility shift assay that this chemically labeled protein retained DNA mismatch binding property. Consequently, we used [TBP(Eu 3+)]-MutS to develop a faster and simpler semidirect HTRF assay.

Covalent integration of luminescent Eu (III) complex onto composite conductors or semiconducting substrates by grafting with organosilane

A method to introduce the luminescent rare earth complex onto Si and indium tin oxide substrates by grafting with organosilane was presented. The organosilane, 3-aminopropyltriethoxysilane, was used as molecular bridge to link 5-(7-bromoheptyl)-5′-methyl-2,2′-bipyridine to the activated substrates. Europium complex, Europium tris(2-thenoyltrifluoroacetonato)(2,2′-bipyridine), was then incorporated to the substrates via coordination reaction. The surface chemical composition and surface morphology of modified substrates were investigated by X-ray photoelectron spectroscopy and atomic force microscopy, respectively. The electrochemical characterization, fluorescence microscopy and photoluminescence analysis were utilized to confirm the Europium complex formation on the substrates.

Spectral-luminescent properties of low-defect organic glasses doped with europium tris(benzoyltrifluoroacetonate)

Spectral-luminescent properties of low-defect organic glasses doped with europium tris(benzoyltrifluoroacetonate)

Temperature dependent photoluminescence down to 4.2 K in EuTFC

The temperature dependence of photoluminescence in Europium tris[3-(trifluoro-methylhydroxymethylene)-( + )-camphorate] (EuTFC) embedded in polymer films has been examined from 40 K down to 4.2 K with the goal of preparing sensor films for low-temperature thermal imaging. The behavior of EuTFC showed significant difference when based on polystyrene compared to poly( n-alkyl methacrylate)s. In poly( n-alkyl methacrylate)s prepared by standard methods for imaging applications, the photoluminescence is fully saturated below 30 K, whereas in polystyrene films there is a strong temperature dependence even down to 4.2 K. By optimizing the preparation procedure for films made of poly(butyl methacrylate) (PBMA) and poly(methyl methacrylate), also these polymers became very sensitive down to liquid helium temperature. The maximum temperature sensitivity of EuTFC in PBMA is found to be 1.0 % / K at 4.2 K. The problem of delamination and cracking of the polymer film at cryogenic temperature is also avoided by the special preparation method.

Thermal behavior of europium tris(hexafluoroacetylacetonate) Eu(hfa)3 and the mixed-ligand 4-cyanopyridine-N-oxide complex [Eu(hfa)3(cpo)

The thermal behavior and thermodynamic properties of europium tris(hexafluoroacetylacetonate) Eu(hfa)3 and the mixed-ligand 4-cyanopyridine-N-oxide complex [Eu(hfa)3(cpo)] were investigated by thermal analysis and Knudsen effusion mass spectrometry. The compounds sublime congruently. The composition of the gas phase over the compounds and the partial pressures of the components were determined. The enthalpies of sublimation, polymerization, and dissociation of these compounds were derived from experimental data.

Preparation, thermal decomposition and lifetime of europium tris(dibenzoylmethanato)phenanthroline complex doped xerogel

The Eu tris(dibenzoylmethanato)phenanthroline complex doped xerogel has been synthesized by a catalyst-free sol-gel roure. The non-isothermal kinetic analysis is calculated by Friedman isoconversional method and multivariate non-linear regression method. The overall decomposition process below 600°C is fitted by an Fn model (n order reaction), corresponding to the dehydration of the matrix, and a two-step consecutive reaction of Cn model (n order autocatalytic reaction), corresponding to the decomposition of organic complex. Correlation coefficient is 0.99986. The lifetime values of xerogel, defined as the 5% decomposition of europium organic complex, indicate that the xerogel can find application at near room temperature.