Synergistic extraction of lanthanum(III) from chloride medium by mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazalone-5 and triisobutylphosphine sulphide

The synergistic effect of 1-phenyl-3-methyl-4-benzoyl-pyrazalone-5 (HPMBP) and triisobutylphosphine sulphide (TIBPS, B) is investigated in the extraction of lanthanum(III) from chloride solution. Lanthanum(III) is extracted by the mixture as LaCl₂·PMBP·B_0.5 instead of La(PMBP)₃·(HPMBP) which is extracted by HPMBP alone. The equilibrium constants and thermodynamic functions such as ΔG, ΔH and ΔS are determined. The extraction of other rare earth ions by mixtures of HPMBP and TIBPS is also studied and the possibility of separating rare earth ions is discussed.     

Preparation and properties of rare-earth containing oxide fluoride glasses

The preparation of the rare earth containing oxide fluoride glasses LnF₃ (Ln; Y through Lu)-BaF₂-AlF₃-GeO₂ in which the nominal content of LnF₃ reached 60 mol% in maximum and their basic properties such as density, refractive index and glass transition temperature were investigated and summarized in detail. Especially, in order to discuss the local structure around the rare earth ion in the glass, the Judd-Ofelt analysis (discussion with Ω parameters) of the HoF₃-BaF₂-AlF₃-GeO₂ glasses was carried out. The unique fluorescent behavior and the magnetic properties of LnF₃-BaF₂-AlF₃-GeO₂ glasses (Ln = Tb and/or Sm) were also studied.     

Structural changes of (K,Gd)2Ta2O7 pyrochlore at high pressure

The structure of K-bearing tantalate pyrochlore (K_2-xGd_x)Ta₂O_6+x(x∼0.4) was studied at high pressures using in situ X-ray diffraction and Raman scattering methods. Experimental results indicated that (K_2-xGd_x)Ta₂O_6+x(x∼0.4) retains the pyrochlore structure up to 40 GPa, but partial amorphization occurred at pressures above 23 GPa. The amorphous phase was also confirmed in the quenched sample by means of transmission electron microscopy. The tantalate pyrochlore lattice is more stable than pyrochlore compounds in other systems, such as rare earth titanates, zirconates and stannates. The structural stability of pyrochlore tantalate may be mainly related to the size ratio of cations on the 16d and 16c sites in the lattice.     

Asymmetric fluorination of β-keto esters catalyzed by chiral rare earth perfluorinated organophosphates

Novel chiral rare earth metal complexes bearing perfluorinated binaphthyl phosphate ligand RE[(R)-F₈BNP]₃ (RE = rare earth; F₈BNP = 5,5′,6,6′,7,7′,8,8′-octafluoro-1,1′-binaphthyl-2,2′-diyl phosphate) have been synthesized and used as a catalyst for the asymmetric electrophilic fluorination reaction of β-keto esters. The use of Sc[(R)-F₈BNP]₃ catalyst in combination with 1-fluoropyridinium triflate (NFPY–OTf) as a fluorinating agent was found to give the desired α-fluoro-β-keto esters in high chemical yields and enantiomeric excesses (up to 88% ee) under mild conditions.     

The effects of substituents,molecular symmetry,ionic radius of the rare earth metal,and macrocycle on the electronic absorption spectra characteristics of sandwich-type bis(phthalocyaninato) and mixed (phthalocyaninato)(porphyrinato) rare earth complexes

The electronic absorption spectroscopic data for two series of 60 unsubstituted/substituted bis(phthalocyaninato) and mixed [tetrakis(4-chlorophenyl)porphyrinato](phthalocyaninato) rare earth complexes M(Pc)₂, M(Pc^∗)₂ and M(TClPP)(Pc) [M = Y, La…Lu except Pm; Pc^∗ = dianion of 2,3,9,10,16,17,23,24-octakis(4-methoxyphenoxy)phthalocyanine [Pc(MeOPhO)₈], dianion of 3(4),12(13),21(22),30(31)-tetra(tert-butyl)phthalocyanine (TBPc) and TClPP = tetra(4-chloro)phenylporphyrin] have been measured in CHCl₃. In this paper, the influence of the symmetry of macrocycle rare earth molecules, the effects of ionic radius of the rare earth metal and the influence of substituent species (tert-butyl and 4-methoxyphenoxy groups) onto the peripheral benzene rings on the electronic absorption characteristics of sandwich-type compounds have also been tentatively studied in detail.     

Raman scattering in rare earths tetraborides

The Raman spectra of single crystalline RE (rare earth) tetraborides REB₄ (RE = Y, La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Lu) are measured and analysed with respect to the dependence of the phonon frequencies on the rare earth metal. Phonons representing octahedral B₆ units are identified by comparison to the according phonon modes of hexaborides. Their relative force parameters are estimated.     

Rare earth(III) perfluorooctane sulfonates and perfluorooctanesulfonic acid in fluorous solvents: Novel and recyclable catalytic systems for Friedel-Crafts acylation of unactivated benzenes

Catalytic Friedel-Crafts acylation of benzene and unactivated benzenes, such as chlorobenzene and fluorobenzene, was successfully accomplished using rare earth(III) perfluorooctane sulfonates (RE(OPf)₃), RE = Sc, Y, La ∼ Lu) and perfluorooctanesulfonic acid (PfOH) as catalysts in fluorous solvents. Solutions of Yb(OPf)₃ and PfOH in perfluorodecalin (C₁₀F₁₈, cis and trans-mixture) are the most suitable catalytic system, with catalyst loading as low as 0.4%mol leading to clean, high-yielding benzoylation of a variety of unactivated benzenes. By simple separation of the fluorous phase containing only catalyst, acylation can be repeated several times.     

Regioselective allylation reactions using crotyl Grignard reagent-CeCl3 systems

Regioselective allylation reactions using crotyl Grignard reagent-CeCl₃ systems are described. Regioselectivity depends on the lanthanide salts: α-product was predominantly produced with light rare earth elements such as La, Ce, Pr, Nd, whereas γ-product was formed when heavy rare earth elements were used.     

Electro‐kinetic Separation of Rare Earth Elements Using a Redox‐Active Ligand

Purification of rare earth elements is challenging due to their chemical similarities. All of the deployed separation methods rely on thermodynamic properties, such as distribution equilibria in solvent extraction. Rare‐earth‐metal separations based on kinetic differences have not been examined. Herein, we demonstrate a new approach for rare‐earth‐element separations by exploiting differences in the oxidation rates within a series of rare earth compounds containing the redox‐active ligand [{2‐(t BuN(O))C₆H₄CH₂}₃N]³⁻. Using this method, a single‐step separation factor up to 261 was obtained for the separation of a 50:50 yttrium–lutetium mixture.     

Physical properties of layered homologous RE-B-C(N) compounds

Physical properties of a series of homologous RE-B-C(N) B₁₂ cluster compounds REB₁₇CN, REB₂₂C₂N, and were investigated. The structures of the compounds are layer-like along the c-axis, with rare earth and B₆ octahedral layers separated by B₁₂ icosahedral and C-B-C chain layers whose number increases successively from two B₁₂ layers for the REB₁₇CN compound to four for the REB_28.5C₄ compound. The rare earth atoms are configured in two triangular flat layers which are stacked on top of one another in AB stacking where the nearest-neighbor rare earth directions are the three atoms forming a triangle in the adjacent layer. The series of homologous compounds exhibit a spin glass transition with T_f shifting in correspondence with variations of the basal plane lattice constants, consistent with the magnetic interaction being effective in the basal planes. The isothermal remanent magnetization shows a stretched exponential decay . Exponents determined for the different homologous compounds were scaled as a function of T_r=T/T_f and found to follow the empirical dependency determined for typical spin glasses. It is indicated that a mixture of disorder originating from the partial occupancy of the rare earth sites and frustration of interactions due to the unique configuration is responsible for the manifestation of spin glass transitions in these homologous systems.     

A new bicomponent catalyst for NOx reduction in oxygen-rich atmosphere

The NO_x catalytic reduction in oxygen-rich atmosphere using propene as a reductant is studied. A Mn-perovskite-type catalyst containing rare earth in A site and copper in B site substitution is synthesized. Then, it is supported as clusters on a silicon carbide ceramic sponge, where alumina has previously been deposited. This catalyst is tested for NO_x reduction reaction and the influence of gas space velocity, oxygen and propene concentrations is investigated. NO_x conversion may reach 75 % under certain conditions. The activity of such a catalyst is explained by the formation of carbon on the surface of the alumina and its interaction with the perovskite.     

Stabilization of the γ form of the rare earth sesquisulfides at lower temperature by doping with Calcium

The preparation of several samples forming a solid solution that can be formulated as Ca_(3/2)yR_2−y_{0.25−(1/2)y}S₃ (R = Ce, Sm, Gd) (0 ≤ y ≤ 0.30) is reported, together with their structural characterization, mainly through transmission electron microscopy. The introduction of Ca²⁺ into the rare earth metal sesquisulfide matrix stabilizes the γ form phase at 900 °C. This effect can be related to the non-stoichiometric nature of this phase, R_3−x_xS₄, because the introduction of Ca²⁺ requires the elimination of cation vacancies from the structure: 2R³⁺ + → 3Ca²⁺ (R = rare earth metal;  = cation vacancies). However, a NaCl-type solid solution is formed for R = Eu, formulated as Eu_1−yCa_yS. Well-ordered crystals are found in every sample, as it is revealed by transmission electron microscopy images and diffraction patterns. The color properties of the samples have been evaluated with reflectance spectra in the visible range and with L*–a*–b* coordinates.     

Mannich-type reaction of (1-methoxy-2-methylpropenyloxy)trimethylsilane with arylaldehydes and aromatic amines catalyzed by perfluorinated rare earth metal salts in fluorous phase

In this paper, we describe a useful Mannich-type reaction in fluorous phase. By use of perfluorodecalin (C₁₀F₁₈, cis- and trans-mixture) as a fluorous solvent and perfluorinated rare earth metal salts such as Sc(OSO₂C₈F₁₇)₃ or Yb(OSO₂C₈F₁₇)₃ (2.0 mol%) as a catalyst, the Mannich-type reaction of arylaldehydes with aromatic amines and (1-methoxy-2-methylpropenyloxy)trimethylsilane can be performed for many times without reloading the catalyst and the fluorous solvent.     

Interpretation of the crystal field parameters by the angular overlap model - application to some fn electron systems

In this paper, we interpret crystal field parameters in the angular overlap model of Jørgensen, involving σ and π effects. We have studied some trivalent rare earth ions in several compounds: KY₃F₁₀, the aluminates LnAlO₃, LaCl₃ and Ln(OH)₃. In all cases σ effects are dominant; e_σ values decrease as the atomic number of the rare earth ion increases. For the rare earth fluorine bonding the obtained values for e_π are the greatest. It may also be noted that e_σ and e_π parameters are connected with the B₆^m crystal field parameters. Finally, we have shown for several compounds, the existence of a power law especially for σ effects.     

Reaction between rare earth elements and HFNO2 solution

Rare earth elements react with HFNO₂ solution to produce nitrosylium fluorometallates (NO)_xLnF_x+3. The value of x is 1.0 or 1.5 for light rare earth elements and 0.5 or 1.0 for heavy rare earths. Nitrosylium fluorometallates of rare earth elements can be decomposed into the simple fluoride and nitrosyl fluoride at low temperatures (46–68°C).     

Phosphate uptake behavior of layered rare earth hydroxides l-RE(OH)3 (RE = Sm,Gd, Er,and Y) from water

The use of rare earths (REs) provides various advantages for removal and recovery of phosphate from water because they have high affinity to form stable complexes with phosphates even at low concentrations. Very low solubility of rare earth phosphate REPO₄ in water was expected to induce a high phosphate adsorption rate and capacity. In this study, layered rare earth hydroxides, l-RE(OH)₃ (RE = Sm, Gd, Er, and Y), have been employed to remove or recover phosphate from aqueous solution. This layered polymorph of l-RE(OH)₃, which is composed of hydroxocation layers, exhibited a high point of zero charge (pH_pzc > 10) and significantly enhanced adsorptive ability for phosphates over a wide pH range. The isotherm and kinetics of phosphate adsorption on l-RE(OH)₃ were explained dominantly by the Langmuir isotherm model and pseudo-second-order kinetic model, respectively. A strong dependence of isotherm and kinetic parameters on RE demonstrated that the adsorption of phosphate on l-RE(OH)₃ is a chemisorption dominated process involving the replacement of –OH by phosphate ion to be included into the coordination polyhedra of RE. The desorption of phosphate from l-RE(OH)₃ was slow but the desorption efficiency for all RE members was higher than 97% in a 1.0 M NaOH solution after 4 days at room temperature. Considering high capacity and stability as well as no significant interference in recovery of phosphate from waters containing common competing anions, this rare earth adsorbent series is proposed as a promising alternative for efficient and sensitive phosphate recovery from natural and wastewaters.     

Synthesis and structural study of the new rare earth magnesium borates LnMgB5O10 (Ln = La, …, Er)

To obtain rare earth luminescent materials with weak concentration quenching, the B₂O₃-rich portion of the ternary diagram Ln₂O₃MgOB₂O₃ (Ln = rare earth) has been investigated. A ternary phase of composition LnMgB₅O₁₀ has been found for Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er. These compounds all crystallize in the monoclinic space group $\text{P2}{}_1\text{c}$. The structure has been determined on a LaMgB₅O₁₀ crystal. A full-matrix least-squares refinement leads to R = 0.039. The structure can be described as being made of (B₅O₁₀^5?)_n two-dimensional layers linked together by the lanthanum and magnesium ions. The rare earth atom coordination polyhedra form isolated chains. These borates are isostructural with some rare earth cobalt borates.     

Enthalpies of formation of rare earth orthovanadates, REVO4

Rare earth orthovanadates, REVO₄, having the zircon structure, form a series of materials interesting for magnetic, optical, sensor, and electronic applications. Enthalpies of formation of REVO₄ compounds (RE=Sc, Y, Ce-Nd, Sm-Tm, Lu) were determined by oxide melt solution calorimetry in lead borate (2PbO·2B₂O₃) solvent at 1075 K. The enthalpies of formation from oxide components become more negative with increasing RE ionic radius. This trend is similar to that obtained for the rare earth phosphates.     

Evidence for the change of inner-sphere hydration number of rare earth ions in the middle of the series

Glass transition temperatures of aqueous solutions of rare earth chlorides and perchlorates have been measured. The anomalous T_g change in the middle of the senes is interpreted as evidence for the coordination number change of rare earth ions, in accordance with the views expressed by Spedding et al. in 1966.     

Infrared evolved gas analysis during thermal investigation of lanthanum, europium and samarium carbonates

The characterisation of rare earth elements carbonates (REECs) was performed by thermal analysis (TG-DTG) combined with simultaneous infrared evolved gas analysis-Fourier transform infrared (EGA-FTIR) spectroscopy. The TG-DTG curves were obtained using the Perkin-Elmer PC series TGA-7 thermogravimetric analyser in the temperature range 25-800 °C both in dynamic air and nitrogen atmosphere.La₂(CO₃)₃·nH₂O, Eu₂(CO₃)₃·nH₂O and Sm₂(CO₃)₃·nH₂O were analysed, the dehydration and decarbonation steps were investigated and the water content was calculated. The trace rare earth elements in lanthanum, europium and samarium carbonates were determined by Philips PU 7000 inductively coupled plasma atomic emission spectrometry (ICP-AES) and the concentration of REE ranged from 6.2×10⁻⁵ to 4.2×10⁻⁴% (w/w).