Europium Compounds Research Articles

A 121Sb and 151Eu Mössbauer Spectroscopic Investigation of EuCd2X2 (X = P, As, Sb) and YbCd2Sb2

AbstractThe pnictides EuCd2X2 (X = P, As, Sb) and YbCd2Sb2 were synthesized from the elements or a EuCd2 precursor in tantalum tubes. The samples were characterized by powder X‐ray diffraction. The structure of EuCd2As2 was refined on the basis of single‐crystal X‐ray diffractometer data: CaAl2Si2 type, P$\bar{3}$m1, a = 444.99(9), c = 735.0(1) pm, wR2 = 0.0372, 200 F2 values and 10 variables. The two‐dimensional [Cd2X2] networks consist of edge‐sharing CdX4/4 tetrahedra. The networks are separated and charge‐balanced by the europium and ytterbium atoms. Redetermination of the magnetic properties revealed divalent europium and ytterbium. YbCd2Sb2 is diamagnetic. For the europium compounds only one magnetic phase transition is evident, i.e. TC = 11.6 K for EuCd2P2, TN = 9.5 K for EuCd2As2, and TN = 7.4 K for EuCd2Sb2. 151Eu Mössbauer spectra show full magnetic hyperfine field splitting at 4.2 K. A transferred hyperfine field of 7.1 T is evident in the 4.2 K 121Sb spectrum of EuCd2Sb2.

Syntheses, crystal structures, magnetic properties and vibrational spectra of nitridoborate-halide compounds Sr2[BN2]Br and Eu2[BN2]X(X= Br, I) with isolated [BN2]3–units

AbstractThe title compounds Sr2[BN2]Br (1), Eu2[BN2]Br (2) and Eu2[BN2]I (3) were obtained from reactions of mixtures of Sr3[BN2]2and SrBr2(1) and the binaries EuN, h-BN and EuX2(X= Br, I) (2,3), respectively. The crystal structure of Sr2[BN2]Br was solved from X-ray powder diffraction data and those of the europium compounds from X-ray single crystal data. Sr2[BN2]Br and Eu2[BN2]Br are isotypic crystallizing in the rhombohedral space groupR-3m(No. 166, Pearson code:hR18;Z= 3;a= 4.11692(2) Å,c= 26.4611(2) Å (1);a= 4.0728(3) Å,c= 26.589(3) Å (2)). The crystal structures are built up by layers of condensed edge-sharing [B—N—B]@Eu6and [Br]@Eu6trigonal antiprisms, which are alternately stacked along [001]. Eu2[BN2]I – isotypic to Sr2[BN2]I – crystallizes in the monoclinic space groupP21/m(No. 11, Pearson code:mP24;Z= 4;a= 10.2548(6) Å,b= 4.1587(3) Å,c= 13.1234(9) Å,β= 91.215(4)°). The crystal structure is characterized by slightly puckered layers formed by condensed edge sharing I@Eu6octahedra which are separated by isolated [BN2]3–units. The bond lengths for the strictly linear [BN2]3–anions in(1)and(2)ared(B—N) = 1.351(4) Å and 1.356(8) Å, respectively. In Eu2[BN2]I two crystallograhically distinct [BN2]3–anions are present withd(B1—N) = 1.32(4) Å, 1.37(4) Å andd(B2—N) = 1.30(4) Å, 1.34(4) Å, respectively. Their bond angles vary slightly: ∠(N—B1—N) = 179(3)° and ∠(N—B2—N) = 177(3)°. The magnetic susceptibility data of the europium compounds (2) and (3) indicate that the Eu ions are divalent with 4f7configuration. Vibrational spectra were measured and interpreted based on theD∞hsymmetry of the discrete linear [N—B—N]3–moieties, considering the site symmetry reduction and the presence of two distinct [BN2]3–groups in (3).

Structure, spectral and luminescence properties of compounds of europium(III) with nicotinic acid and enrofloxacin

The compounds of Eu(III) with nicotinic acid and enrofloxacin are synthesized. Their composition and structure are proved by the data of elemental analysis, IR and luminescence spectroscopy, powder and single crystal X-ray diffraction. By single crystal X-ray diffraction, the structure of the compound of Eu with nicotinic acid is identified as a centrosymmetric dimer with 4 carboxylate bridges of the composition Eu2(C6H4NO2)6·4H2O. The Stark structure of the 5D0-7Fj transitions in the mixed-ligand compounds of Eu(III) with nicotinic acid and enrofloxacin is determined. The bands of IR spectra are assigned; the conclusion about the bidentate coordination of ligands is made.

Luminescent and magnetic properties of europium compounds with cinnamic acid

The temperature dependences of the molar magnetic susceptibility of luminescent europium compounds with cinnamic acid [Eu(Cin)3]n and Eu(Cin)3 · 2D · H2O (where Cin is the cinnamic acid anion and D is phen (1,10-phenanthroline) or dipy (2,2-dipyridyl)) were studied at temperatures from 300 to 2 K. The molar magnetic susceptibility of the compounds increased in the series Eu(Cin)3 · 2dipy · H2O < Eu(Cin)3 · 2phen · H2O < [Eu(Cin)3]n. The energy distances λlum between the 7F0 ground level and the 7F1 state in the luminescence spectra correlated well with λmagn obtained from magnetochemical data.

Direct study of the f-electron configuration in lanthanide systems

The valence shell electron configurations within a few electron volts above the Fermi level in cerium, ytterbium, europium and samarium compounds were probed by resonant X-ray emission spectroscopy (RXES) at the L3 absorption pre-edge. The rare earth systems show distinct spectral signatures depending on the f-electron configuration. The high energy resolution experimental results reported here are well reproduced by atomic multiplet calculations confirming the localized character of the 4f electrons. The magnitude of the electron–electron interactions within the 4f shell and between 3d and 4f electrons is analyzed. The present technique is a powerful tool for the study of the 4f valence electron configuration that, unlike L3 absorption spectroscopy at the main edge, is little influenced by valence electron relaxation following core hole creation.

Benzene Trisulfonic Acid (H3BTS) as Analogue of Trimesic Acid for Building Open Frameworks: The First Rare Earth Examples [La(BTS)(H2O)5] and [RE(BTS)(H2O)4] (RE = Nd, Sm, Eu)

AbstractThe reaction of benzene 1,3,5‐trisulfonic acid (H3BTS) with the hydroxides RE(OH)3 (RE = La, Nd, Sm, Eu) in aqueous solution afforded the sulfonates [La(BTS)(H2O)5] and [RE(BTS)(H2O)4] (RE = Nd, Sm, Eu). Single crystal investigations were performed for the lanthanum and the europium compound, respectively. [La(BTS)(H2O)5] is triclinic [P$\bar{1}$, Z = 2, a = 783.18(6) pm, b = 1056.94(8) pm, c = 1082.38(8) pm, α = 114.860(2)°, β = 96.655(3)°, γ = 104.402(3)°] whereas [Eu(BTS)(H2O)4] exhibits monoclinic symmetry [P21/n, Z = 4, a = 767.61(5) pm, b = 1730.2(1) pm, c = 1134.06(8) pm, β = 108.375(8)°]. Despite these crystallographic differences, the structural features of the lanthanum and europium compounds are very similar. They show the metal ions connected by BTS anions to layers that are further linked by hydrogen bonds. Interestingly, only two of the three sulfonate groups are connected to rare earth ions, whereas the third remains uncoordinated and acts as acceptor within the hydrogen bonds. According to powder XRD measurements the neodymium and samarium sulfonates are isotypic with the europium compound. The thermal analyses of the compounds show the dehydration in a temperature range between 100 and 300 °C, whereas the decomposition of the organic ligands takes place at temperatures as high as 550 °C. Thus the anhydrous sulfonates are much more stable than comparable salts of trimesic acid. The residues of the thermal decompositions were identified by XRD experiments.

Synthesis, Crystal Structure and Fluorescence Property of Terbium Coordination Polymers with Pyridine-3.5-Dicarboxylic Acid

Rare-earth metal-organic frameworks [Tb2(pdc)3(H2O)9]n3nH2O, were synthesized and characterized by elemental analysis, IR spectra and single-crystal X-ray diffraction. The title compound consisted of one-dimensional dual-chains, in which each metal atom is nine-coordinated with oxygen atoms. The carboxylate groups of pdc provided two kinds of coordination ways as bidentate and monodentate. The solid-state photoluminescence measurement exhibited green light-emitting characteristic of terbium (III) coordination polymer, and the fluorescence intensities were stronger than that of the europium compound with the same ligand.

2,5-Bis{N-(2,6-diisopropylphenyl)iminomethyl}pyrrolyl Complexes of the Divalent Lanthanides: Synthesis and Structures

The reaction of potassium 2,5-bis{N-(2,6-diisopropylphenyl)iminomethyl}pyrrolyl, [(DIP2pyr)K], with the anhydrous lanthanide diiodides resulted in the heteroleptic complexes [(DIP2pyr)LnI(THF)3] (Ln = Sm, Eu, Yb). All complexes are monomeric in the solid state, which is remarkable, since samarium and europium complexes tend to form dimeric complexes bridged by iodine ions. The (DIP2pyr)− ligands are coordinated almost symmetrically in a κ3 N, N′, N′′ mode to the metal center in the samarium and europium compounds. In contrast, for the ytterbium complex an asymmetric coordination mode was observed.

ChemInform Abstract: A New Type of Divalent Europium Compound MEuPO4 (M: K, Rb, Cs), Its Synthesis, Crystal Structure, and Properties.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis of Rare Earth (Oxo)nitridocarbonates by Employment of Supercritical Carbon Dioxide, Single‐source Precursor, Solid‐State, and Ion Exchange Reactions

AbstractNovel synthetic approaches to rare earth nitrido‐ and oxonitridocarbonates are described. Dioxy mono‐carbodiimides (Ln2O2CN2) from the second half of the lanthanide series are accessible by insertion of supercritical CO2 into lanthanide amido compounds (e.g. [(Cp2ErNH2)2]), forming single‐source precursors. Ammonolyses of amorphous carbamate compounds afford phase pure Ln2O2CN2, which are also accessible via the crystalline carbamate compound [Ln2{μ‐η1:η2‐OC(OtBu)NH}Cp4] (Ln = Y, Ho, Er, Yb). Urea complexes and homoleptic cyanates of europium and strontium were synthesized by solid‐state reaction of urea with the respective metals. Subsequent thermal treatment (160–240 °C) results in formation of solvent‐free homoleptic cyanates. The Eu2+‐doped compounds [Sr(OCN)2(urea)]:Eu2+ and Sr(OCN)2:Eu2+ as well as the respective pure europium compounds exhibit strong broad band emissions due to 4f65d1–4f7 transitions in the bluish green region. Furthermore, rare earth dicyanamides Ln[N(CN)2]3·2H2O as well as Ln[N(CN)2]3 (with Ln = Eu, Tb, and Gd) were prepared by ion exchange in aqueous solution, followed by evaporation of the solvent at room temperature. Condensed nitridocarbonates such as rare earth tricyanomelaminates [NH4]Ln[HC6N9]2[H2O]7·H2O (Ln = La–Nd, Sm–Dy) were obtained through ion exchange reactions. The luminescence properties of the europium and terbium dicyanamides as well as the tricyanomelaminates have been explored in detail.

Structural regularities and luminescence properties of dimeric europium and terbium carboxylates with 1,10-phenanthroline (C.N. = 9)

A systematic comparison of the spectroscopic and structural data for series of related dimeric lanthanide carboxylates with 1,10-phenanthroline Ln(RCOO) 3·Phen (Ln = Eu, Gd, Tb): 1-naphthylcarboxylates, benzoates, 2-furancarboxylates, phenoxyacetates, caproates, acetates, propionates, 3-nitropropionates was undertaken in search for methods of regulation of quantum yield of the Ln 3+ luminescence and for paths of the control of excitation energy transfer. The crystal structures of europium propionate and europium and terbium 3-nitropropionates were solved by X-ray diffraction methods. Effect of stepwise distortions of Ln coordination polyhedron derived from X-ray data of the succession of compounds, which determine details of the charge distribution in the surroundings of the Ln 3+ ion, on luminescence spectra, on lifetimes of Ln 3+ states, and on efficiency of Ln 3+ luminescence was investigated. Polyhedron distortions are to a great extent caused by the range of the Ln–O bond lengths related to bridging-cyclic carboxylic group that is conditioned by the type and the size of carboxylate anion. Relative contributions of the rates of radiative and various nonradiative processes to the lifetimes of europium 5D 0 and terbium 5D 4 metastable states were estimated. Multiphonon relaxation is the main nonradiative process in europium compounds at temperatures from 77 to 295 K and in terbium compounds at low temperatures, but the radiative processes are appreciably prevailing. Dependence of the lifetimes due to radiative processes determined from the integral intensity of europium 5D 0– 7F J transitions related to the intensity of magnetic-dipole 5D 0– 7F 1 transition on distortions of Eu polyhedron in the sequence of compounds is in agreement with the same dependence obtained from the measured lifetimes, if nonradiative processes are taken into account. A back energy transfer from 5D 4 state of Tb 3+ ions to the lowest triplet state related to Phen molecule in most of compounds studied is another nonradiative process contributing to quenching in terbium compounds at high temperatures. An influence of this process on luminescence intrinsic quantum yield can be predominant. It leads to abrupt lowering the luminescence intensity of some terbium carboxylates, for example, benzoate at increasing the temperature. It was found, that lifetime of 5D 4 state and luminescence efficiency of terbium compounds at high temperatures depend on the bonding strength of Phen ligand with Tb 3+ ion. A range of the lowest triplet state energies of Phen ligand, from 20,850 to 21,750 cm −1, was revealed in lanthanide carboxylates under investigation. Closeness of the natural lifetimes of 5D 0 and 5D 4 states of Eu 3+ and Tb 3+ ions, respectively, in the same charge surroundings was demonstrated.

Europium(ii) compounds: simple synthesis of a molecular complex in water and coordination polymers with 2,2′-bipyrimidine-mediated ferromagnetic interactions

Reaction between EuCl(2) and 2,2'-bipyrimidine (bpm) in de-oxygenated water afforded a cationic molecular complex [EuCl(bpm)(2)(H(2)O)(4)][Cl]·H(2)O (1). When performed in an organic solvent such as THF or methanol, the same reaction yielded a 3-dimensional coordination polymer of formula [EuCl(2)(bpm)(MeOH)(0.5)](∞) (2) in which both bpm and the chloride ions act as linkers between the Eu(II) ions. Upon replacing Cl(-) by I(-), two coordination polymers of formula {[Eu(bpm)(2)(H(2)O)(3)][I](2)·0.5bpm}(∞) (3) and {[Eu(I)(bpm)(MeOH)][I]}(∞) (4) were obtained from reaction in water and methanol, respectively. All these compounds were characterized by X-ray crystallography. Investigations of the magnetic properties revealed a weak antiferromagnetic coupling in 2, while 3 and 4 showed a weak ferromagnetic coupling at low temperature.

Synthesis, characterization and thermal behaviour of solid-state compounds of europium(III) and gadolinium(III) 3-methoxybenzoate

Solid-state Ln–C8H7O3 compounds, where Ln stands for Eu(III) and Gd(III) and C8H7O3 is 3-methoxybenzoate, have been synthesized. Simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, infrared spectroscopy, elemental analysis and complexometry were used to characterize and to study the thermal behaviour of these compounds. The results led to information about the composition, dehydration, thermal stability and decomposition of the isolated compounds.

Eu TZn ( T=Pd, Pt, Au) with TiNiSi-type structure—Magnetic properties and 151Eu Mössbauer spectroscopy

The europium compounds Eu TZn ( T=Pd, Pt, Au) were synthesized from the elements in sealed tantalum tubes in an induction furnace. These intermetallics crystallize with the orthorhombic TiNiSi-type structure, space group Pnma. The structures were investigated by X-ray diffraction on powders and single crystals: a=732.3(2), b=448.5(2), c=787.7(2) pm, R 1/ wR 2=0.0400/0.0594, 565 F 2 values for EuPdZn, a=727.8(3), b=443.7(1), c=781.7(3) pm, R 1/ wR 2=0.0605/0.0866, 573 F 2 values for EuPtZn, and a=747.4(2), b=465.8(2), c=789.1(4) pm, R 1/ wR 2=0.0351/0.0590, 658 F 2 values for EuAuZn, with 20 variables per refinement. Together the T and zinc atoms build up three-dimensional [ TZn] networks with short T–Zn distances. The Eu TZn compounds show Curie–Weiss behavior in the temperature range from 75 to 300 K with μ eff=7.97(1), 7.70(1), and 7.94(1) μ B/Eu atom and θ P=18.6(1), 34.9(1), and 55.5(1) K for T=Pd, Pt, and Au, respectively, indicating divalent europium. Antiferromagntic ordering was detected at 15.1(3) K for EuPdZn and canted ferromagnetic ordering at 21.2(3) and 51.1(3) K for EuPtZn and EuAuZn. 151Eu Mössbauer spectroscopic measurements confirm the divalent nature of the europium atoms by isomer shift values ranging from −8.22(8) (EuPtZn) to −9.23(2) mm/s (EuAuZn). At 4.2 K full magnetic hyperfine field splitting is observed in all three compounds due to magnetic ordering of the europium magnetic moments.

Synthesis and structure of complex compounds of lanthanum, europium, and scandium iodides with antipyrine

Synthesis and X-ray single-crystal diffraction study of antipyrine complexes of lanthanum, europium, and scandium iodides were performed. In all compounds, the inner coordination sphere of the complex cation is an octahedron formed by antipyrine molecules coordinated through the oxygen atoms of the C=O groups.

The Ba 2LnFeNb 4O 15 “tetragonal tungsten bronze”: Towards RT composite multiferroics

Several Niobium oxides of formula Ba 2LnFeNb 4O 15 (Ln = La, Pr, Nd, Sm, Eu, Gd) with the “tetragonal tungsten bronze” (TTB) structure have been synthesised by conventional solid state methods. The neodymium, samarium and europium compounds are ferroelectric with Curie temperature ranging from 320 to 440 K. The praseodymium and gadolinium compounds behave as relaxors below 170 and 300 K respectively. The praseodymium, neodymium, samarium, europium and gadolinium compounds exhibit magnetic hysteresis loops at room temperature originating from traces of a barium ferrite secondary phase. The presence of both ferroelectric and magnetic hysteresis loops at room temperature allows considering these materials as composites multiferroic. Based on crystal-chemical analysis we propose some relationships between the introduction of Ln 3+ ions in the TTB framework and the chemical, structural and physical properties of these materials.

R3Au6+xAl26T (R = Ca, Sr, Eu, Yb; T = Early Transition Metal): a Large Family of Compounds with a Stuffed BaHg11 Structure Type Grown from Aluminum Flux

A collection of new quaternary intermetallic compounds with a cubic, stuffed BaHg(11) structure type has been synthesized by the combination of a divalent rare earth or alkaline earth metal R, an early transition metal T, and gold in an excess of molten aluminum. Structural characterization of these R(3)Au(6+x)Al(26)T compounds by powder and single crystal X-ray diffraction indicates that the unit cell varies with the radii of the early transition metal T and the rare earth/alkaline earth R as expected. The element T (where T = group 4, 5, 6, and 7 element) appears to be responsible for the stabilization of up to 43 different members of the R(3)Au(6+x)Al(26)T family of compounds. Varying amounts of disorder and trends in partial occupancies of the Au stuffed site--the site that is vacant in the parent compound BaHg(11)--are also indicated by the diffraction studies of this family of compounds. Magnetic susceptibility data reveals that the transition metal atoms in these materials do not possess local magnetic moments. For the magnetic rare earth containing materials, the europium compounds undergo a ferromagnetic transition at 10 K, and the ytterbium analogues show mixed valent behavior. Band structure calculations also support a mixed valent state for Yb in these compounds.

Photodegradation and photostabilization of europium compounds in polyvinyl chloride

The photolysis kinetics was studied, and methods were suggested for photostabilization of complexes of europium with β-diketones and europium cinnamates and quinaldates in polyvinyl chloride.

The luminescent properties of polyethylene films with admixtures of luminophores based on europium compounds

Polyethylene films activated with europium(III) complexes with carboxylic acids and Eu(L)3 · nD · xH2O + ANT compositions, where L is the trifluoroacetic, toluyl, or cinnamic acid anion and ANT is anthranilic acid, were prepared. The intensity of luminescence of the polymeric compositions depended on the content of luminophores (molar ratio between europium compounds and anthranilic acid). An analysis of the excitation spectra showed that, in polymer—Eu(L)3 · nPhen · xH2O + ANT compositions, there was effective energy transfer from phenanthroline to anthranilic acid levels.

A series of rare earth coordination polymer constructed from paddle-wheel building blocks

Three coordination polymers, Ln 2(bpdc) 3(phen) 2(H 2O) 2 (Ln=Nd(1), Eu(2), and Tb (3); bpdc=2,2′-bipyridine-3,3′-dicarboxylate; phen=1,10-phenanthroline), were obtained by hydrothermal reaction of Ln 2O 3 with 2,2′-bipyridine-3,3′-dicarboxylate acid, and 1,10-phenanthroline. They were characterized by single-crystal X-ray diffraction, IR spectra, and photoluminescent spectra. The crystallographic data of 1–3 indicated that they were isostructural. Both complexes contained paddle-wheel building blocks, formed by bpdc and phen ligands. These paddle-wheel secondary building units (SBUs) were further connected to form two-dimensional (2-D) metal organic framework (MOF) networks by 2,2′-bipyridine-3, and 3′-dicarboxylate linkers. A three-dimensional (3-D) supramolecular structure was formed by π–π aromatic interactions between adjacent 2-D infinite networks. Photoluminescent measurements indicated that europium compound 2 and terbium compound 3 were strong, red and green emitters, respectively.