Mixed borohydride-chloride complexes of the rare earth elements

Mixed borohydride-chloride complexes of lanthanum and neodymium having the 2,5-bis{N-(2,6-diisopropylphenyl)iminomethyl}pyrrolyl ligand in the coordination sphere were synthesised by the reaction of potassium 2,5-bis{N-(2,6-diisopropylphenyl)iminomethyl}pyrrolyl [(DIP₂-pyr)K] with a 1:1 mixture of [Ln(BH₄)₃(THF)₃] and LnCl₃ (Ln = La, Nd). Both compounds are dimeric in the solid state. The metal atoms are bridged almost symmetrically by two μ-chlorine atoms. Quantum chemical calculations for the lanthanum compound were performed to obtain a deeper insight into the bonding in the molecule.     

State of the rare earth elements tetapyrazinoporphyrazinate complexes in protic media

Russian Journal of General Chemistry - The acid-base interactions of tetrapyrazinoporphyrazine erbium(III) and lutetium(III) complexes in the media based on acetic and trifluoroacetic acids were...     

Thermal properties of rare earth elements complexes with 1,3,5-benzenetricarboxylic acid

Summary Rare earth elements 1,3,5-benzenetricarboxylates were prepared as solids of the general formula Ln(C₉H₃O₆)·nH₂O, where n=6 for La-Dy and n=4 for Ho-Lu,Y. Their solubilities in water at 293 K are of the order 10^-4-10^-6 mol dm^-3. The IR spectra of the complexes indicate that the carboxylate groups are bridging and bidentate chelates. Hydrated 1,3,5-benzenetricarboxylates lose water molecules during heating in one step (La-Tb), two steps (Y, Ho-Tm) or three steps (Dy, Yb, Lu). The anhydrous complexes are stable up to 573-742 K and decompose to oxides (Ce-Lu) at higher temperatures.     

辉光放电质谱法测定稀土矿中的15种稀土元素

利用高纯铜粉与稀土矿石粉末均匀混合压片制样.混合15种高纯稀土氧化物制样建立标准工作曲线,校正15种稀土元素相对灵敏度因子,再进行定量分析.结果 表明,稀土元素工作曲线的线性方程相关系数R2均大于0.996,相对标准偏差(RSD)小于5％,满足定量分析要求.测定结果与电感耦合等离子体质谱法(ICP-MS)和电感耦合等离...     

Determination of the stability constants for the complexes of rare earth elements and tetracycline

Stability constants for the lanthanide elements complexes with tetracycline were determined by the methods of average number of ligands, the two parameters and by weighted least squares. The technique of solvent extraction was applied to obtain the values of the parameters required for the determination of the constants.     

A novel efficient approach to heteronuclear triple-decker complexes of rare earth elements with phthalocyanines

A novel approach to heteroleptic heteronuclear rare earth metal(III) trisphthalocyaninates was proposed with the complexes [(15C5)₄Pc]M*[(15C5)₄Pc]M(Pc) as examples (15C5 is 15-crown-5, Pc^2? is the phthalocyaninate dianion, and M* ?? M = Yb and Y). Unsubstituted lanthanum bisphthalocyaninate, La(Pc)₂, was used for the first time as a Pc^2? donor in the synthesis of such complexes. This substantially increased the yields of the target heteronuclear complexes over the previous literature data.     

Thermal decomposition of cellulose hyphan and its complexes with rare earth elements and scandium

Thermal decomposition of cellulose hyphan (CH) and its complexes with Lu, Gd, Nd and Sc under an atmosphere of air has been studied using thermogravimetry (TG), differential thermogravimetry (DTG) and differential thermal analysis (DTA). The results showed that, a different stages are accompanying the decomposition of (CH) and its complexes. These stages are affected by the presence of the metal ions. On the basis of the applicability of a non-isothermal kinetic equation, it was demonstrated that three main stages are involved in the decomposition processes. The activation energies of the different stages are calculated.

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Zusammenfassung Mittels TG, DTG und DTA wurde die thermische Zersetzung von Cellulosehyphan (CH) und seiner komplexe mit Lu, Gd, Nd und Sc an Luft untersucht. Es zeigte sich, da\ die Zersetzung von (CH) und seiner Komplexe von verschiedenen Schritten begleitet werden. Diese Schritte werden durch die Gegenwart der Metallionen beeinflu\t. Unter der Annahme der Anwendbarkeit einer nichtisothermen kinetischen Gleichung wurde gezeigt, da\ im Zersetzungsproze\ drei Hauptschritte inbegriffen sind. Die Aktivierungsenergie der verschiedenen Schritte wurde berechnet.

     

Solvent extraction kinetics of rare earth elements

The kinetics of solid-liquid extraction of rare earth elements (RE) (La, Ce, Sm, Dy and Yb) were studied with 1-(2-pyridylazo)-2-naphthol (PAN) at 60 degrees C using paraffin wax as a diluent. The rate of extraction is first order with respect to metal ion and hydrogen ion in the aqueous phase and second order with respect to the extractant in the organic phase. The rate-determining step is the formation of an [RE(PAN)(2)](+) complex between RE(3+) and PAN in the aqueous phase. The rate constant for the extraction was found to be about 10(11) 1 mol(-1) s(-1). The temperature dependence of extraction rate was determined and the activation parameters were calculated.     

Distribution characteristics of rare earth elements in plants from a rare earth ore area

The contents of eight rare earth elements (La, Ce, Nd, Sm, Eu, Tb, Yb and Lu) in various plant species taken from a rare earth ore area were determined by instrumental neutron activation analysis. For a given plant, the REE patterns in root, leaf and host soil are different from each other. The REE distribution characteristics in roots of various species are very similar and resemble those in the surface water. The results of this study suggest that there is no significant fractionation between the REEs during their uptake by the plant roots from soil solution. However, the variation of the relative abundance of individual REE occurs in the process of transportation and deposition of REEs in plants.     

A spectrographic method for determining the stability constants of complexes of the rare earth elements

A new spectrographic method has been proposed for determining the concentrations and stability constants of rare earth element (REE) complexes from the relative intensity of the bands in the absorption spectra when several complexes are present in the solution. The proposed method has been checked for the case of the gluconate and iminodiacetato complexes of neodymium. The values of the stability constants determined by the spectrographic method show satisfactory agreement with the values obtained by other methods.     

Energy-adjusted pseudopotentials for the rare earth elements

Nonrelativistic and quasirelativistic energy-adjusted pseudopotentials and optimized (7s6p5d)/[5s4p3d]-GTO valence basis sets for use in molecular calculations for fixed f-subconfigurations of the rare earth elements, La through Lu, have been generated. Atomic excitation and ionization energies from numerical HF, as well as SCF pseudopotential calculations using the derived basis sets, differ by less than 0.1 eV from numerical HF all-electron results. Corresponding values obtained from CI(SD), CEPA-1, as well as density functional calculations using the quasirelativistic pseudopotentials, are in reasonable agreement with experimental data.     

Double molybdates of rare earth elements and zirconium

The results of the study of Ln₂(MoO₄)3—Zr(MoO₄)₂ molybdate systems, which made it possible to obtain new double molybdates, are summarized. The specific features of phase formation in double salt systems were determined and the formation of phases with the compositions given by three formulas Ln₂Zr₃(MoO₄)₉ (Ln = La—Tb), Ln₂Zr₂(MoO₄)₇ (Ln = Sm—Y), and Ln₂Zr(MoO₄)₅ (Ln = Tb—Lu) was established. Phase diagrams of the systems were constructed and the interrelation between the composition and the structure of the obtained phases was determined; in addition, crystallographic, thermal, and dielectric characteristics of the obtained compounds were studied.     

Reversed-phase thin-layer chromatography of the rare earth elements

Summary Partition chromatographic behaviour of the rare earth elements on C₁₈ bonded silica reversed-phase material has been investigated by thin-layer chromatography in methanol — lactate media. The rare earth lactato complexes are distributed and fractionated on bonded silica layers without ion-interaction reagents. The concentration and pH of lactate solution, methanol concentration and temperature have effects on the migration and resolution of the rare earth elements. The partition system is particularly suited to separate adjacent rare earths of middle atomic weight groups, allowing the separation of gadolinium, terbium, dysprosium, holmium, erbium and thulium to be achieved by development to 18 cm distance.     

Sorption in the chemistry of rare earth elements

Sorption methods for the concentration and separation of rare earth elements are reviewed. Sorbents based on organic polymers, specifically strongly and weakly acidic cation exchangers, anion exchangers, and complexing sorbents, are successively considered. Data on the use of inorganic sorbents and solid phase extractants in the rare earth chemistry are also given. Considerable attention is paid to hybrid organomineral materials constituting a promising class of sorbents. Advantages and disadvantages of using biosorbents, molecularly imprinted sorbents, and nanosorbents for the concentration and separation of rare earths are discussed.