Europium Compounds Research Articles

Europium and terbium pyrrole-2-carboxylates: Structures, luminescence, and energy transfer

Lanthanide pyrrole-2-carboxylates [{Ln(L)3(H2O)2}·H2O]n (Ln = Eu, Gd, Tb) were synthesized and investigated using single crystal X-ray diffraction and optical spectroscopy (luminescence, luminescence excitation and vibrational IR spectra). The europium pyrrole-2-carboxylate crystallizes as a 2D network structure in the P21/c space group. The Eu3+ coordination polyhedron formed by five carboxylic groups and two water molecules can be described as a distorted single-capped square antiprism. The luminescence spectra indicate a low symmetry of the charge distribution around the Ln3+ ion that corresponds to the C1 symmetry of the coordination environment of Eu3+ ion in the [{Eu(L)3(H2O)2}·H2O]n crystal lattice. The low-energy ligand–metal charge transfer (LMCT) state was identified in the europium compound. The shortening of the 5D0 (Eu3+) lifetime in the 230–295 K temperature region, when the compound is heated from 77 to 295 K, and the low luminescence intensity of the europium pyrrole-2-carboxylate are caused by the participation of the LMCT state in quenching processes. The energy of activation determined for the 5D0 – LMCT crossover is 3900 ± 100 cm−1.

PREPARATION AND PHOTOLUMINESCENT PROPERTIES OF COMPLEXES OF TERBIUM, EUROPIUM AND THEIR COPRECIPITATES WITH METHYL ETHER 2-HYDROXYBENZOIC ACID

The amorphous coordination compounds of terbium (III) and europium (III) with methyl ester of 2-hydroxybenzoic acid, as well as their mixtures (coprecipitate), in the composition of TbxEu(1-x)L2OH·H2O, are isolated in a solid state by the method of coprecipitation from a weakly basic aqueous-ethanolic medium. According to elemental analysis and pH potentiometric studies, neutralization of cations’ charges is carried out by two molecules of dissociating ligand and one hydroxyl group. The method of thermogravimetric analysis has established that the water molecule that is part of the complexes is coordinated. According to the IR spectroscopy, the coordination of the ligand is carried out with the help of the oxygen atoms of the dissociating hydroxyl and the carbonyl group of the ester fragment. The obtained compounds are not volatile and when the mass spectra are registered in the BBA mode, they are completely destroyed. The complex of terbium (x = 1) in solid state exhibits an effective sensitized luminescence of green color, which is due to the intramolecular transfer of excitation energy from the ligand to the Tb3+ ion. The europium containing complex (x =0), which is isomorphic to terbium one, when excited by UV light, practically does not radiate due to the discrepancy between the energies of the triplet level of the ligand and the emission level of the Eu3+ ion. Sensitized f-f luminescence of the Eu3+ of red color be realized in solid precipitates of the complex mixture (x <1) due to the intermolecular transfer of the excitation energy from the terbium complex (III) to the compound of europium (III) (columinescence). The intensity of the glow of europium (III) depends on the ratio of ion emitters and reaches the maximum value at the values of Tb: Eu = 7: 3. At the same time there is a corresponding decrease in the intensity of the glow of terbium (III).

Люминесцентные свойства соединений европия(III) с хинолиновой кислотой и фосфорсодержащими нейтральными лигандами

AbstractLuminescent mixed-ligand europium(III) complexes with quinolinic acid and phosphorus-containing neutral ligands with a dimeric structure of the composition Eu_2(QA)_3 · 3Н_2О, Eu_2(QA)_3 · D · 2Н_2О, where QA is quinolinic acid and D is hmpa (hexamethylphosphortriamide), tppo (triphenylphosphinoxide), (hmpa), or Et_6pa (hexaethylphosphortriamide), are synthesized. The thermal and spectral-luminescent properties of the synthesized complex mixed-ligand europium(III) compounds are studied. It is shown that the detachment of water and neutral ligand molecules during thermolysis occurs in two stages with endothermic effects and that the complex compounds are stable at temperatures up to 320°С. It is found by IR spectroscopy that quinolinic acid coordinates to the europium(III) ion by two carboxylate ions. The low luminescence intensity of mixed-ligand europium(III) quinolinates is explained by inefficient electronic excitation energy transfer from quinolinic acid and phosphorus-containing neutral ligands to europium ions.

Recognition of Oligosaccharides by Chirality Induced in Europium (III) Compounds.

Identification of saccharides is difficult due to their similar chemical structure. However, they interact very selectively with lanthanide probes. To explore the potential for saccharide recognition, we compare circularly polarized luminescence induced by a variety of oligo- and polysaccharides in three europium compounds. Measurement on a standard Raman optical activity spectrometer made it possible to use high excitation powers and provided very distinct spectral patterns, which were sensitive both to the local structure and differences in molecular size. For example, α-, β- and γ-cyclodextrins provided unique spectroscopic responses. Titration data and molecular dynamics simulation confirmed that CPL spectra carry information about the binding mode and strength between the lanthanide probe and saccharide skeleton.

RETRACTED ARTICLE: Four Ln-coordination polymers: synthesis, crystal structure, fluorescent sensing of nitrobenzene and Tb3+, and catalytic properties

We, the Editors and Publisher of Journal of Coordination Chemistry, have retracted the following article:Yu-Yuan Tang, Shuang Chen, Cui-Juan Wang, Zi-Xin Zhu & Dong-Ning Liu. Four Ln-coordination polymers: synthesis, crystal structure, fluorescent sensing of nitrobenzene and Tb3+, and catalytic properties. Journal of Coordination Chemistry 71.19 (2018) 3207-3221. DOI: 10.1080/00958972.2018.1517257Since publication it has come to our attention that there are duplications of data for the europium compound (compound 1) presented in the above 2018 article and the terbium compound presented in the below 2017 article.Yu-Yuan Tang, Cui-Juan Wang, Shuang Chen & Hai-Yu Dai. A terbium(III) organic framework as a fluorescent probe for selectively sensing of organic small molecules and metal ions especially nitrobenzene and Fe3+. Journal of Coordination Chemistry 70.24 (2017) 3996-4007. DOI:10.1080/00958972.2017.1413490The cell constants presented in the two papers for the two different compounds are identical, including the esds for the lengths of the axes and the absence of esds on the bond angles. Examination of the submitted CIFs for the two compounds showed identical information plus additional data, including the crystal dimensions. The deposited hkl files for the two different compounds are identical, indicating that the same crystal data was used for the two compounds.Following COPE guidelines, Taylor & Francis has contacted the authors as well as their affiliated institution with a request for clarification, however the explanation we received has not been satisfactory. As such, we are retracting both papers as it is clear data has been duplicated between the two structures. The authors were informed of this decision and have since agreed to the retraction.We have been informed in our decision-making by our policy on publishing ethics and integrity and the COPE guidelines on retractions.The retracted articles will remain online to maintain the scholarly record, but they will be digitally watermarked on each page as “Retracted”.

Thermodynamic Analysis of the Oxidation of Radioactive Graphite in the Na2CO3–K2CO3–Sb2O3 Melt in an Argon Atmosphere

Abstract—Graphite is used as a neutron moderator and reflector. Moreover, graphite can be used as sealants and bearings in reactors. The graphite mass in a reactor is 1–2 ths t. A large amount of radioactive graphite wastes forms when graphite reactors are taken out of service. The existing methods of processing radioactive graphite are based on its isolation from the environment. These methods cannot substantially decrease the volume of radioactive graphite wastes. As a result, the processing of irradiated reactor graphite by oxidation in molten salts can be considered as an alternative reclamation method, which can decrease the volume of radioactive graphite wastes. The oxidation of radioactive graphite in the Na2CO3–K2CO3–Sb2O3 melt in an argon atmosphere is thermodynamically simulated using the TERRA software package. The data obtained are used to analyze the distribution of elements over condensed and gas phases. Heating of the system to 1073 K is found to cause the evaporation of the condensed compounds of antimony and cesium. Upon heating to 1273 K, the condensed compounds of potassium, sodium, and chlorine evaporate. Heating to 1373 K leads to the evaporation of the condensed compounds of nickel. Heating to 1673 K brings about the evaporation of the condensed compounds of uranium, calcium, and strontium. Heating to 1773 K causes the evaporation of the condensed compounds of plutonium, beryllium, americium, and europium. At temperatures above 1773 K, only a vapor–gas phase exists in the system.

Thermodynamic Analysis of the Oxidation of Radioactive Graphite in a Multicomponent Melt in an Inert Atmosphere

Graphite occupies a specific place among the entire mass of accumulated radioactive wastes. The problem of reclamation of spent graphite has not yet been solved in the world. The behavior of radioactive graphite in the multicomponent CuO–NaCl–KCl–Na2CO3–K2CO3 melt in an argon atmosphere in the temperature range 373–3273 K is studied by thermodynamic simulation with the Terra software package, which is intended for calculating the phase compositions and the thermodynamic and transport properties of arbitrary systems. The calculation was performed using a database on the properties of individual substances. At 1273 K, graphite burns to form carbon monoxide and carbon dioxide. The condensed compounds of cesium, chlorine, and uranium evaporate at 1573 K. An increase in the system temperature to 1873 K leads to the vapor pressure of condensed nickel. Condensed strontium oxide transforms into a vaporized state at 2273 K. The condensed compounds of plutonium, calcium, and europium transforms into a vaporized state at 2373 K. Condensed beryllium oxide evaporates at 2473 K. A further increase in the temperature to 2673 K leads to the evaporation of condensed americium(III) oxide. Only a vapor–gas phase is present in the isolated system in the temperature range 2673–3273 K.

Luminescent Properties of Europium(III) Compounds with Quinaldic Acid and Neutral Phosphorus-Containing Ligands with a Dimeric Structure

New luminescent mixed-ligand complexes of europium(III) with quinaldic acid and neutral phosphorus-containing ligands with a dimeric structure are synthesized. The structure and the thermal, spectral, and luminescent properties of mixed-ligand europium(III) complexes are studied. It is shown that the quinaldinate ion is coordinated to a europium(III) ion in a bidentate fashion. It is found that the excitation energy transfer to europium (III) ion occurs from levels of quinaldic acid and neutral phosphorus-containing ligands.

Photoluminescence of europium and terbium trifluoroacetylacetonates. Participation of LMCT state in processes of the energy transfer to Eu3+ ion

The effect of fluorination on spectroscopic properties of europium and terbium trifluoroacetylacetonates Ln(TFAA)3·2H2O, Ln(TFAA)3·Phen and Ln(TFAA)3·Bpy in the solid state have been investigated. A threefold increase in the luminescence intensity of europium compounds at -CF3 for −CH3 substitution in the β-diketonate ligand was obtained at 77 and 295 K. Different mechanisms of the excitation energy transfer to Ln3+ ions in europium and terbium compounds, which result in a drop in the luminescence efficiency at elevated temperatures, have been analyzed. A key role of ligand-metal charge transfer (LMCT) states in the processes of sensitization of the europium trifluoroacetylacetonates is demonstrated. Expansion of the energy gap between the LMCT state and the lowest triplet state T1 at fluorination gives rise to an increase in the excitation efficiency of the Eu3+ luminescence at 295 K. The back-transfer energy 5D4-T1 in the terbium trifluoroacetylacetonates is the main reason for shortening the 5D4 lifetime and decreasing the luminescence efficiency. The energy dissipation processes in the lanthanide TFAA adducts with heterocyclic diimines are mainly related to the β-diketonate ligand.

Effective and efficient detection of pH fluctuations based on ratiometric metallic-ciprofloxacin architectures

The availability of lanthanide ciprofloxacin complexes and the exploration of efficient new ways to the target species have made fluorescent signals as essential tools for chemical sensing. Both terbium (III) and europium (III) compounds possess easily distinguished, line-like emission bands occurring in the green and red region respectively. Based on the steps of ionizations and the coordination structure changes, the two molecular probes give rise to unique pH-sensitivities at different conditions. The photoluminescence properties of the mixture for the two complexes are demonstrated. At pH from 3 to 6, the Eu(III) emission is found to be less affected and the solution emits blue light in acidic environment (pH = 3). The terbium (III) characteristic luminescence exhibited off-on changes within a narrow pH range (pH = 5–6). Further spectroscopic pH titrations (pH from 6 to 10) are performed and the Eu (III) red emission has been significantly improved. The molecular-based probes have excellent water solubility, negligible cytotoxicity and enough permeability to across cell membrane. Such pH-responsive performance has been carried out for the investigation of intracellular pH measurement and these novel pH indicators were considered to be suitable for detecting bio-medical samples.

Synthesis and Luminescent Properties of Europium Complexes Covalently Bonded to Hybrid Materials Based on MCM-41 and Poly(Ionic Liquids).

Due to the wide potential application in the fields of sensing, lighting materials, and optical–electrical multifunctional devices, rare earth complex hybrid materials have been studied extensively over the past decades. A poly(ionic liquid)/mesoporous-based hybrid system which has been functionalized by the covalently linked europium complexes was reported here. Through surface modification with a coupling agent bearing an vinyl group, MCM-41 was chosen as the carrier matrix for poly(ionic liquids) (PILs) and europium compounds, and based on that, novel luminescent hybrid materials were prepared by confining the ionic liquid and europium complexes into the inorganic Si–O frameworks. The resulting organic/inorganic materials are chemically bonded hybrids which show good photoluminescent properties such as broad excitation spectra, line-like emission spectra, and long luminescence lifetimes. The PILs/MCM-41/Eu3+ hybrid reported here is a rare earth multifunctional material which is believed to have potential applications in the field of optical–electrical materials.

Spectral-Luminescence Properties of Europium(III) Compounds with Two Different β-Diketones

Complex luminescent mixed-ligand compounds of europium(III) with two different β-diketones have been synthesized. Spectral-luminescence properties of complex europium(III) compounds have been investigated. The copresence of two different β-diketones in the europium(III) coordination sphere results in expansion of the spectral-absorption range, as well as in luminescence-intensity growth.

RETRACTED ARTICLE: A terbium(III) organic framework as a fluorescent probe for selectively sensing of organic small molecules and metal ions especially nitrobenzene and Fe3+

We, the Editors and Publisher of Journal of Coordination Chemistry, have retracted the following article:Yu-Yuan Tang, Cui-Juan Wang, Shuang Chen & Hai-Yu Dai. A terbium(III) organic framework as a fluorescent probe for selectively sensing of organic small molecules and metal ions especially nitrobenzene and Fe3+. Journal of Coordination Chemistry 70.24 (2017) 3996-4007. DOI:10.1080/00958972.2017.1413490Since publication it has come to our attention that there are duplications of data for the terbium compound presented in the above 2017 article and the europium compound (compound 1) presented in the following 2018 article.Yu-Yuan Tang, Shuang Chen, Cui-Juan Wang, Zi-Xin Zhu & Dong-Ning Liu. Four Ln-coordination polymers: synthesis, crystal structure, fluorescent sensing of nitrobenzene and Tb3+, and catalytic properties. Journal of Coordination Chemistry 71.19 (2018) 3207-3221. DOI: 10.1080/00958972.2018.1517257The cell constants presented in the two papers for the two different compounds are identical, including the esds for the lengths of the axes and the absence of esds on the bond angles. Examination of the submitted CIFs for the two compounds showed identical information plus additional data, including the crystal dimensions. The deposited hkl files for the two different compounds are identical, indicating that the same crystal data was used for the two compounds.Following COPE guidelines, Taylor & Francis has contacted the authors as well as their affiliated institution with a request for clarification, however the explanation we received has not been satisfactory. As such, we are retracting both papers as it is clear data has been duplicated between the two structures. The authors were informed of this decision and have since agreed to the retraction.We have been informed in our decision-making by our policy on publishing ethics and integrity and the COPE guidelines on retractions.The retracted articles will remain online to maintain the scholarly record, but they will be digitally watermarked on each page as “Retracted”.

Luminescence properties of europium(III) compounds with quinaldic acid and nitrogen-containing ligands

Luminescent mixed-ligand Eu(III) complexes with quinaldic acid and nitrogen-containing dimeric ligands are synthesized. The thermal and spectral-luminescent properties of the obtained mixedligand Eu(III) complexes are studied. It is shown that a water molecule and a neutral ligand are detached during thermolysis in two stages with endothermic effects. It is found that the quinaldinate ion is coordinated to a europium(III) ion in a bidentate fashion. The Stark structure of the 5D0–7F j (j = 0, 1, 2) transitions in the low-temperature luminescence spectra of europium(III) complexes is analyzed.

Mechanical Characterization of EuD4TEA‐ and ZnS:Mn‐Enhanced Composites

AbstractTriboluminescent (TL) materials are assessed as components in structural health monitoring (SHM) systems within polymer composites. Processing must be addressed due to particle characteristics such as density, morphology, and chemical makeup, all of which can affect polymer curing dynamics and thermo‐mechanical properties. This study considers key processing parameters during incorporation of TL compounds into various polymers. The TL materials chosen for this study are zinc sulfide manganese (ZnS:Mn) and europium dibenzoylmethide triethylammonium (EuD4TEA). These crystals are dispersed within the liquid phase of polyvinyl ester (VE), polydimethylsiloxane (PDMS), and Dymax 9663 ultraviolet‐curable (UV‐curing) resins. Incorporation of the europium compound apparently slows the cure process, particularly in the UV‐curing resin, while the zinc compound had a minimal effect on curing. Tensile testing shows a decrease in tensile modulus due to incorporation of TL crystals. Incorporation of the europium compound caused a 20–53% decrease in modulus; incorporation of the zinc compound caused a 7–66% decrease in modulus. Experimental results are used to create a multi‐scale model using Digimat. Discrepancies in the found values may be due to sample quality (e.g. presence of voids in experimental samples).

Effect of sol maturation on the preparation of luminescent ormosils

ABSTRACTAn UV‐polymerization approach was proposed to construct luminescence organic‐inorganic hybrid. Methacryloxypropyltrimethoxysilane (MAPTMS) was chosen as sol–gel precursor to prepare the host matrix and acrylic europium Eu(AA)3 was used as guest dopants. Structural modifications during irradiation were evident in both the inorganic and organic domains of the hybrid material. The influence of condensation degree of the silicate network on the photopolymerization kinetics of organic moieties was investigated. It appeared that the sol maturation time was of vital importance to the phase homogeneity and optical transparency of materials. To get more efficient copolymerization and higher luminescence intensity of the target ormosils, two key processing factors including incorporation time and entrapping concentration are reported. Incorporation time when acrylic europium was introduced into the matrix during sol maturation is found to be helpful to overcome phase separation. The effect of entrapping concentration of europium(III) compound on the luminescence performance was further studied. Material synthesized by this approach has three advantages: optical transparency with little phase separation, organic and inorganic composite with interpenetrating network, covalent grafting of acrylic europium without luminescent species leakage. This “photopolymerization of molecular grafting” strategy is hopeful to offer a promising development for luminescent ormosil glasses. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45146.

Synthesis of EuS and EuSe particles via thermal decomposition of dithio- and diselenophosphinate europium complexes

New two- and trivalent europium complexes with dithio- and diselenodiphenylphosphinate ligands (S2PPh2- and Se2PPh2-) have been synthesized as precursors for nanoparticles. Two-valent europium compounds have been characterized via X-ray diffraction. Their photoluminescence properties have been studied as well. EuS colloidal nanoparticles have been obtained via the thermolysis of Eu(S2PPh2)n (n = 2, 3) in a hexadecylamine medium at 310°C. The average size of objects is found to be 40–70 nm. As is established, the valent state of a lanthanide in the complex exerts no influence on the size of the forming nanoparticles or on the luminescence spectrum of colloidal solutions.

Magnetic Structure of Divalent Europium Compound EuGa4Studied by Single-Crystal Time-of-Flight Neutron Diffraction

The magnetic structure of the intermetallic compound EuGa$_4$ was investigated using single-crystal neutron diffraction with the time-of-flight (TOF) Laue technique on the new diffractometer SENJU at MLF of J-PARC. In spite of high neutron absorption of Eu, a vast number of diffraction spots were observed without isotope enrichment. The magnetic reflections were appeared at the positions with the diffraction indices of $h+k+l{\neq}2n$ below 16 K, indicating that the ordering vector is ${\bf q}=(0~0~0)$. Continuous evolution of magnetic reflection intensity below $T_{\rm N}$ follows a squared Brillouin function for $S$=7/2. By adopting a wavelength-dependent absorption collection, the magnetic structure of EuGa$_4$ was revealed that a nearly full magnetic moment of 6.4$~{\mu}_{\rm B}$ of Eu lies within the basal plane of the lattice. The present study reveals a well-localized divalent Eu magnetism in EuGa$_4$ and demonstrates a high ability of SENJU to investigate materials with high neutron absorption.

Photolysis of light-transforming polymer materials on the basis of europium(III) nitrate with 1,10-phenanthroline and anthranilic acid

Light-transforming polymer materials on the basis of europium(III) nitrate with 1,10-phenanthroline and anthranilic acid, having an intense luminescence in the 400–650 nm spectral range, were obtained. It is shown that the photostability of the polymer materials on the basis of the obtained compositions is higher than of polymer materials activated by europium(III) compounds. Luminescent and photochemical characteristics of the obtained polymer compositions are determined by the molar ratio of the dopants: the maximum luminescence intensity and photostability is characteristic for the polymeric material containing europium(III) nitrate with 1,10-phenanthroline and anthranilic acid at a molar ratio of 1: 2.

Detection of Sugars via Chirality Induced in Europium(III) Compounds.

Detection and resolution of simple monosaccharides are difficult tasks because their structure is quite similar. The present study shows that circularly polarized luminescence (CPL) induced in europium complexes provides very specific spectral patterns for fructose, mannose, glucose, and galactose. Differences were also observed between bare Eu(3+) ion and its complexes, when interacting with these sugars. The CPL spectra were measured on a Raman optical activity (ROA) spectrometer, which ensured high fluorescence intensity owing to the strong 532 nm laser excitation. The induced fluorescence was recorded in the same spectrum as the vibrational Raman bands. On the basis of the ligand field theory, most fluorescence spectral peaks could be assigned to f-shell europium transitions. Additional information on the interaction of the lanthanide with the sugar component was provided by measurement of time-dependent fluorescence, as formation of different complexes led to variations in fluorescence decay times. In nuclear magnetic resonance (NMR), the paramagnetic metal ion interacting with the sugars caused specific changes in (13)C chemical shifts. The spectroscopic data and molecular dynamics modeling showed that the interaction between the monosaccharides and Eu ion is rather weak due to the competition of the OH sugar groups with water molecules. However, multiple binding modes are possible, which contributes to the complexity and specificity of the spectra. The induced chirality and fluorescence spectra thus appear to be convenient means for monosaccharide detection and identification.