Photophysical Properties of Lanthanide Hybrids Covalently Bonded To Functionalized MCM-41 by Modified Aromatic Carboxylic Acids

MCM-41 mesoporous silica has been functionalized with aromatic carboxylic acids salicylic acid (Sal) and 2-hydroxyl-3-methylbenzoic acid (HMBA) through co-condensation approach of tetraethoxysilane (TEOS) in the presence of the cetyltrimethylammonium bromide (CTAB) surfactant as a template. Organic ligands salicylic acid or 2-hydroxyl-3-methylbenzoic acid grafted to the coupling agent 3-(triethoxysilyl)-propyl isocyanate (TEPIC) was used as the precursor for the preparation of an organic–inorganic hybrid materials. Novel organic–inorganic mesoporous luminescent hybrid containing Ln³⁺ (Tb³⁺, Eu³⁺) complexes covalently attached to the functionalized ordered mesoporous MCM-41, which were designated as Ln-Sal-MCM-41 and Ln-HMBA-MCM-41, respectively, were obtained by sol–gel process. The luminescence properties of these resulting materials were characterized in detail, and the results reveal that luminescent mesoporous materials have high surface area, uniformity in the mesopore structure and good crystallinity. Moreover, the mesoporous material covalently bonded Tb³⁺ complex (Tb-Sal-MCM-41 and Tb-HMBA-MCM-41) exhibit the stronger characteristic emission of Tb³⁺ and longer lifetime than the corresponding Eu-containg materials Eu-Sal-MCM-41 and Eu-HMBA-MCM-41 due to the triplet state energy of modified organic ligands Sal-TEPIC and HMBA-TEPIC match with the emissive energy level of Tb³⁺ very well. In addition, the luminescence lifetime and emission quantum efficiency of ⁵D₀ Eu³⁺ excited state also indicates the efficient intramolecular energy transfer process in Tb-SAL-MCM-41 and Tb-HMBA-MCM-41.     

Synthesis and luminescent properties of complexes of Eu(III) with 2-thienyltrifluoroacetonate, terephthalic acid and phenanthroline

This work reports the synthesis and luminescent properties of complexes of europium(III) with 2-thienyltrifluoroacetonate (HTTA), terephthalic acid (TPA) and phenanthroline (Phen), in the solid state. The new complexes were characterized by elemental analysis, infrared (IR) spectroscopy, scanning electronic microscopy (SEM) and thermal stability analysis. Both binuclear complex Eu₂(TPA)(TTA)₄Phen₂ and polynuclear complex Eu(TPA)(TTA)Phen present better thermal stability than the mononuclear complex Eu(TTA)₃Phen does. The formation of the binuclear/polynuclear structure of the complexes appears to be responsible for the enhancement of the thermal stability. The emission spectra show narrow emission bands that arise from the ⁵D₀→⁷F_J (J=0-4) transition of the Eu³⁺ ion. The spectral data of the complexes Eu(TPA)(TTA)Phen and Eu₂(TPA)(TTA)₄Phen₂ present only one sharp peak in the region of the ⁵D₀→⁷F₀ transition indicating that only one Eu³⁺ ion species is present in each sample. In addition, the luminescence decay curves of the complexes Eu(TPA)(TTA)Phen and Eu₂(TPA)(TTA)₄Phen₂ fit a single-exponential decay law. The values of quantum efficiencies of the emitting ⁵D₀ level for the complexes Eu(TPA)(TTA)Phen and Eu₂(TPA)(TTA)₄Phen₂ are 29% and 28%, respectively.     

Synthesis, characterization, and oxygen sensing properties of Ru(II) complex covalently grafted to mesoporous MCM-41

Novel oxygen sensing materials consisting of [Ru(Bphen)₂bpy]²⁺ (Bphen=4,7-diphenyl-1,10-phenanthroline, bpy=2,2′-bipyridyl) portion covalently grafted to the backbones of the ordered functionalized mesoporous MCM-41 are synthesized by co-condensation of tetraethoxysilane (TEOS) and the functionalized Ru(II) complex [Ru(Bphen)₂Bpy-Si]²⁺ using surfactant cetyltrimethylammoniumbromide (CTAB) as template. The Bpy-Si was used as not only one of the precursors of the sol-gel process but also the second ligand of Ru(Bphen)₂Cl₂·2H₂O complex to prepare the functionalized mesoporous materials for oxygen sensors. Dye leaching shortcoming is overcome due to the Si-C bonds. The derivative mesoporous oxygen sensing materials are characterized by Fourier transform infrared (FT-IR), small angle X-ray diffraction (SAXRD), luminescence intensity quenching Stern-Volmer plots, and excited-state decay analysis. The mesoporous materials show higher sensitivity to the O₂ concentration in N₂ (I₀/I₁₀₀=23.2) and shorter response time (1.2 s) in comparison with those based on sol-gel method. When the concentration of oxygen is 10%, the luminescence intensity of the oxygen sensor can be quenched by 89.9%, suggesting that it is highly sensing at low concentration of oxygen.     

Optical oxygen sensing materials based on a novel dirhenium(I) complex assembled in mesoporous silica

A new dirhenium(I) complex fac-[{Re(CO)₃(4,7-dinonadecyl-1,10-phenanthro -line)}₂ (4,4′-bipyridyl)] (trifluoromethanesulfonate)₂ (denoted as D-Re(I) ) is assembled in MCM-41 and SBA-15 type mesoporous silica support. The emission peaks of D-Re(I) in D-Re(I)/MCM-41 and D-Re(I)/SBA-15 are observed at 522 and 517 nm, respectively. Their long excited lifetimes, which are of the order of microseconds, indicate the presence of phosphorescence emission arising from the metal to ligand charge-transfer (MLCT) transition. The luminescence intensities of D-Re(I)/MCM-41 and D-Re(I)/SBA-15 decrease remarkably with increase in the oxygen concentration, meaning that they can be used as optical oxygen sensing materials based on luminescence quenching. The ratios I₀/I₁₀₀ of D-Re(I)/MCM-41 and D-Re(I)/SBA-15 are estimated to be 5.6 and 20.1, respectively. The obtained Stern-Volmer oxygen quenching plots of the mesoporous sensing materials could be fitted well to the two-site Demas model and Lehrer model.     

Synthesis and characterization of ionic liquid-functionalized alumino-silicate MCM-41 hybrid mesoporous materials

Ionic liquid-functionalized alumino-silicate MCM-41 hybrid mesoporous materials have been synthesized with two-step approach, by means of in situ skeleton doping with aluminium and post surface grafting with N-methylimidazole ionic liquid groups. The samples were characterized by X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), N₂ adsorption-desorption, Fourier transform infrared (FTIR) spectra, ²⁷Al and ¹³C MAS NMR spectra and temperature-programmed desorption (TPD) of NH₃. The results indicated that the bifunctionalized MCM-41 possessed ordered mesostructure. Aluminium was efficiently introduced into the framework of the mesostructure, generating Lewis and Brönsted acid sites. N-methylimidazole ionic liquid groups were covalently grafted onto the surface of mesoporous materials. The as-synthesized bifunctional MCM-41 showed good catalytic performance in the coupling reaction of CO₂ and propylene oxide.     

Luminescence properties of Euβ-diketonates incorporated in cubic mesoporous silica

Luminescent materials have been prepared by wet impregnation of Europium (III) dibenzoylmethane complexes in either non-silylated or silylated mesoporous MCM-48 silica. Silylation and incorporation of the Eu (III) complex were confirmed by Nuclear Magnetic Resonance, N₂-sorption, X-ray diffraction and Infrared spectroscopy. The luminescence properties were investigated at room and high temperatures up to 200 °C. Information on host-guest interactions were collected by analyzing the optical characteristics of the Eu (III) ions in the different media. In particular, the intensity parameter Ω₂ is confirmed to be a useful spectroscopic probe for Eu (III) first coordination shell interaction. The role of the O²⁻—Eu³⁺ charge transfer band and the impact of the silylation on the luminescence properties at room and high temperatures is demonstrated.     

Energy transfer study of the formation, composition, and size of nanostructures of metal ion complexes in aqueous solutions

We studied the luminescence intensity (I _lum) of the ions Eu(III) and Sm(III) in relation to the concentrations of ions Ln(III) and Al(III) in water at pH 7 at an excess of such beta-diketones as p-methoxybenzoyltrifluoroacetone (MBTA), dibenzoylmethane (DBM), and tenoyltrifluoroacetone (TTA) and in the presence of 1,10-phenanthroline (phen) used as a synergistic agent. Both the enhancement of I _lum (Eu(III)) upon addition of Gd(III) (co-luminescence) and the effect of the third ion are found to depend on the order of addition of the ions to the solution and, therefore, on the sequence of formation of nanostructures of complexes of these ions in the solution, in which the transfer of the triplet energy of the organic part of complexes takes place, leading to an enhancement in I _lum (Eu(III)). The intensity I _lum (Eu(III)) is shown to increase equally rapidly upon addition of either Gd(III) or Al(III) to solutions with DBM + phen. In solutions of all the three beta-diketones studied, the Eu(III) ions incorporate better into nanostructures of triply charged ions whose radius is similar to or smaller than the radius of the Eu(III) ions. Our study of the effect that the replacement of H₂O with D₂O exerts of I _lum of 5 × 10^?8 M Eu(III) at different concentrations of ligands shows that, at [Ln(III)] < [OH^?] and at a concentration of beta-diketones smaller than 3 × 10^?5 M, the deuteration affects I _lum(Eu(III)) and, therefore, the first coordination sphere of Eu(III) contains OH groups. It is shown that, in aqueous solutions with 3 × 10^?5 M TTA + 10^?5 M phen, the increase in I _lum(Eu(III)) caused by the introduction of Gd(III) ions results from two processes occurring in the nanostructures of these complexes: the energy transfer from Gd(III) complexes to Eu(III) complexes and the increase of I _lum of Eu(III) itself under the conditions in the solution where the total concentration [Ln] ? [OH^?] and both the photochemical deactivation of Eu(III) and the exchange of its excitation energy for vibrations of the OH groups are suppressed. The reliability of the size estimation of nanostructures of metal complexes is discussed in terms of the effect of these nanostructures on I _lum of chelates of Eu(III).     

Design, synthesis and characterization of a highly luminescent Eu-complex monomer featuring thenoyltrifluoroacetone and 5-acryloxyethoxymethyl-8-hydroxyquinoline

A multi-functional ligand, 5-acryloxyethoxymethyl-8-hydroxyquinoline (Hamq), was synthesized, which contained a polymerizable C=C double bond for the copolymerization with other vinyl monomers and acted as photon antenna able to transfer energy to Eu³⁺ ions effectively. The triplet state energy of Hamq was determined to be 22,370 cm⁻¹ via the phosphorescence spectra of Hamq and its gadolinium complex. The title complex monomer Eu(tta)₂(amq) was prepared by coordination reaction of Hamq with europium isopropoxide and 2-thenoyltrifluoroacetone (Htta) in dry organic solvents under argon atmosphere and characterized by elemental analysis and IR spectrum. The photophysical properties of the complex were studied in detail with UV-vis, luminescence spectra, luminescence lifetime and quantum yield. The complex exhibited nearly monochromatic red emission at 612 nm, a remarkable luminescence quantum yield at room temperature (30.6%) upon ligand excitation and a long ⁵D₀ lifetime (389 μs), which indicated that the ligand Hamq could sensitize the luminescence of Eu(III) ion efficiently in Eu(tta)₂(amq), resulting in a strong luminescence of its copolymer poly[MMA-co-Eu(TTA)₂(amq)] under UV excitation. The excellent luminescence properties of the complex made it not only a promising light-conversion molecular device but also an excellent luminescent monomer.     

Evaluation of intramolecular energy transfer process in the lanthanide(III) bis- and tris-(TTA) complexes: Photoluminescent and triboluminescent behavior

This work reports the energy transfer mechanism process of [Eu(TTA)₂(NO₃)(TPPO)₂] (bis-TTA complex) and [Eu(TTA)₃(TPPO)₂] (tris-TTA complex) based on experimental and theoretical spectroscopic properties, where TTA=2-thienoyltrifluoroacetone and TPPO=triphenylphosphine oxide. These complexes were synthesized and characterized by elemental analyses, infrared spectroscopy and thermogravimetric analysis. The theoretical complexes geometry data by using Sparkle model for the calculation of lanthanide complexes (SMLC) is in agreement with the crystalline structure determined by single-crystal X-ray diffraction analysis. The emission spectra for [Gd(TTA)₃(TPPO)₂] and [Gd(TTA)₂(NO₃)(TPPO)₂] complexes are associated to T→S₀ transitions centered on coordinated TTA ligands. Experimental luminescent properties of the bis-TTA complex have been quantified through emission intensity parameters Ω_λ (λ=2 and 4), spontaneous emission rates (A_rad), luminescence lifetime (τ), emission quantum efficiency (η) and emission quantum yield (q), which were compared with those for tris-TTA complex. The experimental data showed that the intensity parameter value for bis-TTA complex is twice smaller than the one for tris-TTA complex, indicating the less polarizable chemical environment in the system containing nitrate ion. A good agreement between the theoretical and experimental quantum yields for both Eu(III) complexes was obtained. The triboluminescence (TL) of the [Eu(TTA)₂(NO₃)(TPPO)₂] complexes are discussed in terms of ligand-to-metal energy transfer.     

Synthesis, characterization and fluorescence studies of a novel europium complex based sensor

A novel europium(III) complex was synthesized using TTA (α-thenoyltrifluoroacetone) as the first ligand and H₂bpdc (2,2′-bipyridine-3,3′-dicarboxylate) as the second ligand. Elemental analysis, thermal analysis, IR and UV–vis spectrum and fluorescence spectrum of the europium(III) complex were carried out. A characteristic Eu³⁺ fluorescence emission was observed in ethanol–water (1:1) solution, indicating that the complex is stable in solution and the emission of Eu(III) ions was not influenced by the water molecules. The fluorescence emission of the complex was quenched completely by the Co²⁺ and Fe³⁺ ions, but the quenched emission was recovered in the presence of glycine. Moreover, the Eu³⁺ emission was very sensitive to pH, so the complex can be used as pH-dependent fluorescence probe or chemosensors.     

Ln(III)-cored complexes based on 2-thenoyltrifluoroacetone ligand for near infrared emission: Energy transfer pathway and transient absorption behavior

Lanthanide(III)-cored complexes based on 2-thenoyltrifluoroacetone (TTA) ligand for near infrared (NIR) emission have been developed to investigate the energy transfer pathway from the antenna ligand to the Ln³⁺ ion. Their photophysical studies indicate the sensitization of Ln³⁺ luminescence by energy transfer through the excited triplet state of β-diketone ligand. Nanosecond (ns) transient absorption behavior of Ln³⁺-[TTA]₃(terpy) complexes at room temperature is explored. The triplet-triplet absorption spectrum for Gd³⁺-[TTA]₃(terpy) is observed under degassed condition, whereas it is hardly observed in Er³⁺-[TTA]₃(terpy) complex. The sensitizing process in Er³⁺-[TTA]₃(terpy), through the triplet state of TTA ligand to Er³⁺ ion, is also independent on the presence of oxygen. It indicates that the energy transfer rate through the excited triplet state of β-diketone ligand to Er³⁺ ion occurs approximately faster than that of the oxygen quenching rate.     

Enhanced electroluminescence of Eu by Tb in complexes Tb1−xEux(TTA)3Dipy

A series of rare earth ternary compounds of Tb_1−xEu_x(TTA)₃Dipy (HTTA=thenoyltrifluoroacetone, Dipy=2,2′-dipyridyl) have been synthesized, and the characteristics of the compounds have been performed by DTA-TG, IR, UV and fluorescence spectroscopy. Photoluminescence measurements indicated that the complexes of Eu(III) emit strong red luminescence under UV radiation. IR spectra suggest that complexes have been successfully synthesized, and TG curves indicate that the complexes are stable up to a temperature of about 220 °C. The Eu complex was blended with poly(N-vinylcarbazole) (PVK) and spin coated into films, and electroluminescence devices with the structure of Indium Tin Oxide (ITO)/PVK:Tb_1−xEu_x(TTA)₃Dipy/BCP(2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline)/aluminum quinoline (AlQ)/Al were fabricated, the luminescence of Eu³⁺ complexes enhances after doping with Tb³⁺. Therefore, it may be an effective method to improve the EL intensity of the lanthanide complex.     

The nature of the effect of Gd(III) on fluorescence of Ln(III) chelates in water solutions

The intensity of fluorescence of Eu(III) and Sm(III) ions sensitized by molecules of n-benzoyltrifluoroacetone and 1,10-phenanthroline introduced in a water solution in a ratio of 3: 1 is studied as a function of the ion concentration in the solution. The comparison of the fluorescence decay curves of Eu(III) and Sm(III) in D₂O and H₂O (pH≥7) solutions containing 10^?4 M of n-Cl-BTFA and 3×10^?5 M of 1,10-phen and the values of τ_fl of Sm(III) in themselves (51–90 μs) are indicative of an insignificant content of water molecules in the first coordination sphere of ions. The effect of other ions on I _fl and τ_fl of Eu(III) ions is studied under these conditions. The intensity of fluorescence of Eu(III) in solutions of 10^?4 M Cl-BTFA and 3×10^?5 H 1,10-phen is found to increase by 1–2 orders of magnitude in the presence of Y(III) and Gd(III) ions, and the magnitude of this effect is unaffected by deoxygenation of the solution. The introduction of a third ion Nd(III) in the solution is shown to attenuate the influence of Gd(III) on I _fl of Eu(III) for Nd(III) concentrations commensurable with the Eu(III) concentration in the solution. The strength of the influence of Gd(III) ions on I _fl of Eu(III) is found to depend on the method of preparation of the solution. The analysis of the results obtained testifies that inhomogeneities consisting of chelates of lanthanide ions displaced from the water structure appear in water. The presence of these inhomogeneities results in efficient energy transfer from ligands of Gd(III) chelates to Eu(III) chelates, which is the reason for the increasing I _fl of Eu(III). The possibility of using data on the enhancement of I _fl of Eu(III) in the presence of Gd(III) and on the reduction of τ_fl of Eu(III) in the presence of Nd(III) for estimating dimensions and structures of displaced systems is discussed.     

Assemblies, characterization, and luminescent enhancement of organized molecular films based on rare earth complexes

Langmuir-Blodgett (LB) films of different molar percentages of Eu(TTA)₃Phen (TTA=2-thenoyltrifluoroacetone; Phen=1,10-phenanthroline) with Gd(TTA)₃Phen coexisting with arachidic acid (AA) (complexes:AA=1:l, in molar ratio) were fabricated and the luminescence enhancement of Eu(III) in the films was studied in this investigation. The monolayers and LB films were characterized by π-A isotherms, fluorescence microscopy, UV-vis spectroscopy and low-angle X-ray diffraction. High-quality LB films and strongly luminescent films were obtained. It was learned from the present study that an efficient intermolecular energy transfer occurred from Gd(TTA)₃Phen to Eu(TTA)₃Phen in the films, which resulted in the luminescence enhancement effect. According to the proposed model of the “active enhancement circle” the distance of energy transfer from Gd-, Tb-, La-, and Y-complex to Eu-complex were calculated to be 1.2, 1.2, 0.7 and 1.0 nm, respectively.     

Analysis on fluorescence of dual excitable Eu(TTA)3DPBT in toluene solution and PMMA

Photoluminescence of Eu(TTA)₃DPBT (TTA=thenoyltrifluoro-acetonate DPBT=2-(N,N-diethylanilin-4-yl)-4,6-bis(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine) in toluene and PMMA thin film are measured with excitation at 350 and 404 nm, respectively, and analyzed using Judd-Ofelt theory. Under excitation at 350 nm, it is found that Eu(TTA)₃DPBT in toluene has a larger Ω₂ value (14.33×10⁻²⁰ cm²) than that (12.70×10⁻²⁰ cm²) of Eu(TTA)₃Phen (Phen=1,10-phenanthroline) in the same solvent, and has a smaller Ω₂ value (12.70×10⁻²⁰ cm²) in PMMA than that (Ω₂=14.09×10⁻²⁰ cm²) of Eu(TTA)₃Phen in PMMA. At the same time, it can be seen that under excitation at 350 nm Ω₂ value of Eu(TTA)₃DPBT in toluene is larger than that in PMMA. Excited by 404 nm, Ω₂ of Eu(TTA)₃DPBT obtained in toluene and in PMMA are the same as that excited at 350 nm. The transition probability (A), emission cross-section (σ) and the fluorescence branching ratio (β) are also evaluated. The lifetime of ⁵D₀ metastable state is measured on 350 and 404 nm excitation, respectively. For the former situation, it is 455 μs in toluene and 640 μs in PMMA, for the latter it is 460 μs in toluene and 664 μs in PMMA. By comparing absorptions with excitations, it can be found that DPBT is more efficient than TTA as an energy donor. Phosphorescence spectra are also measured to estimate the lowest triplet level and analyze the energy transfer for DPBT and TTA, from which it is found that the energy transfer from TTA to DPBT occurs in the luminescent process.     

Spectroscopic properties of polycrystals of supramolecular europium complexes with bathophenanthroline

Nanostructured supramolecular complex of europium(III) with bathophenanthroline (bphen), with detonation synthesis nanodiamonds (NDs) used as a structure-forming element, has been synthesized for the first time. The characteristics of the Eu(bphen)₂(NO₃)₃ complex and the supramolecular complex with NDs, ND–Eu(bphen)₂(NO₃)₂, are studied and compared using scanning electron microscopy (SEM), luminescence spectroscopy, IR spectroscopy, and electron-spin resonance (ESR) spectroscopy. The luminescence quantum yields of the complexes are estimated by the relative method using a β-diketonate complex of europium (III) with tris(thenoyltrifluoroacetone) and 1,10-phenanthroline (Eu(TTA)₃phen) as a reference. It is found that the ND–Eu(bphen)₂(NO₃)₂ supramolecular complex has a higher photoresistance than the complex without NDs and no worse thermal stability (up to a temperature of +150°C).     

Spectroscopic studies of the lanthanide(III) ions with pyridine carboxylic acid N-oxide ligands and in mixed ligand complexes

A series of Ln(III) complexes with pyridine carboxylic acid-N-oxides (L) Ln-L, and mixed ligand complexes of Ln-L plus bipyridine (bipy) or 1,10-phenanthroline (O-phen) (X) Ln-L-X have been studied. These complexes were characterized in solution using Nd(III) absorption in the spectral range of the ⁴I_9/2 → ⁴G_5/2 transition corresponding to the hypersensitive band, and in the solid state with the use of IR and Eu(III) luminescence spectroscopy. In solutions a series of Nd(III) complexes and mixed ligand complexes has been examined and the formation of binary LnL and LnL₂ complexes and mixed ligand LnL₂X complexes evidenced. Solid complexes of Eu(III) with nicotinic acid N-oxide and ternary with nicotinic acid N-oxide plus phen were studied with the use of Eu(III) luminescence lifetime measurements and IR spectroscopy, proving the formation of binary [Eu(nicN-oxide)₃(H₂O)₂].2H₂O and ternary [Eu(nicN-oxide)₃phen].H₂O complexes.     

Preparation and characterization of carbamoylphosphonate(CMPO) silane grafted on various mesoporous silicas

The carbamoylphosphosphonate silane (CMPO analogue; 2-(diphenylphosphoryl)-N-(3-(triethoxysilyl)propyl) acetamide) modified mesoporous silica was prepared via a post-synthesis grafting method for the effective purification of rare earth elements. The guest CMPO analogue was synthesized by direct coupling reaction of 2-(diphenylphosphoryl) acetic acid and 3-(triethoxysilyl)propan-1-amine. Various mesoporous silicates such as MCM-41, SBA-15, or amorphous silica nanoparticles were adopted as host materials. The resulting surface-modified mesoporous materials were characterized with respect to their structural integrity, surface area, and pore size and the concentration of the CMPO silane species. These CMPO functionalized periodic mesostructured silicates offer the potential of applications as catalysts, sensors, or environmental sorbents.     

Mesoporous material grafted with luminescent molecules for the design of selective metal ion chemosensor

Luminescent Schiff-base groups have been successfully grafted on the surface of mesoporous material MCM-48. The grafted Schiff-base groups were employed to prepare luminescent Schiff-base-Zn complex that was covalently bound to the MCM-48 surface. These luminescent mesoporous materials were characterized with X-ray, UV-VIS and emission spectroscopic methods. Experimental results demonstrated that MCM-48 modified with functional groups exhibited novel luminescent property. The chemosensing property of modified MCM-48 sample was investigated. It was demonstrated that the fluorescence of MCM-48 solid with Schiff-base groups could be completely quenched by Cu²⁺ cation and this mesoporous material was suitable for sensing Cu²⁺ cation in aqueous media.     

A luminescent dinuclear Eu(III) complex based on 2,8-bis(4′,4′,4′,-trifluoro-1′,3′-dioxobutyl)-dibenzothiophene for light-emitting diodes

A dinuclear Eu (III) complex Eu₂(dbt)₃·4H₂O was synthesized, where H₂dbt was 2,8-bis(4′,4′,4′,-trifluoro-1′,3′-dioxobutyl)-dibenzothiophene. The complex emits the characteristic red luminescence of Eu³⁺ ion due to the ⁵D₀→⁷F_J(J=0-4) transitions under 395 nm-light excitation with a luminescent quantum efficiency of 17%. The complex is thermally stable up to 280 °C. It was found that the complex can be effectively excited by a 395 nm-emitting InGaN chip. Bright red light was obtained using the complex as light color-conversion material.