Stabilité des carboxylates de terres rares I Furanne- et thiophène-carboxylates-2

The stability constants of 2-furanecarboxylates and 2-thiophencarboxylates of some rare earths have been determined at ionic strength 0.100 (NaClO₄) at 25.0°C by a potentiometric method. The ligands form 1 : 1 complexes similar to the rare earths propionates.     

Stabilité des carboxylates de terres,III. Maléates,méthylsuccinates et malates

The stability constants of maleates, methylsuccinates and malates of rare earths have been determined at 25.0 °C and at ionic strength 0,100 (NaClO₄) by a potentiometric method. Each ligand forms 1 : 1 and 1 : 2 complexes in aqueous solution, the malates being the most stable. The first and the second dissociation constants of the ligand acids were also measured. The 1 : 2 maleates of La, Pr, Nd, Sm, and Eu have been isolated.     

Stabilité des carboxylates de terres rares,IV N-acétylglycinates

The stability constants of N-acetylgycinates of some rare earths in aqueous solution have been determined by a potentiometric method, and by a solvent extraction technique. The ligand forms 1:1 complexes which are stabilized by relatively large positive entropies of formation, the corresponding enthalpies being endothermic. This backs up the assumption that a conjugate base of an amino acid forms innersphere complexes and acts as a unidentate ligand towards a rare earth cation, like a simple carboxylate.     

Composés d'addition des chlorures de terres rares avec le méthanol,l'éthanol et le propanol-2. Préparations,solubilités et réactions de transsolvatation

By reaction of hydrated rare earths chlorides (M = La, Nd, Sm, Gd, Dy, Er, Yb, Y) with orthoformates, the following adducts have been prepared: MCl₃· 4MeOH, MCl₃ ·3EtOH (M = La, Nd, Sm, Gd, Yb), MCl₄ · 4 EtOH (M = Dy, Er, Y); adducts MCl₃ · 3iso-PrOH have been prepared by successive action of methyl orthoformate and of 2-propanol. The solubilities of these adducts in the corresponding alcohols at 25° (for the lanthanum adducts equally at 0 and 50°) are given. Two examples of the transsolvatation of these compounds, yielding adducts with weakligands, are described.     

对甲基二溴偶氮胂的合成及其与稀土显色反应的研究

本文报道了对甲基二溴偶氮胂的合成,该显色剂在酸性介质中与稀土元素产生高灵敏度显色反应,大多数常见元素不干扰,所拟分析方法已成功地应用于小麦和铝合金中稀土总量的测定     

稀土-蛋氨酸配合物的热力学

在25 ℃和μ=0.15 mol·L~(-1)[NaCl]条件下, 用pH电位法测定了L-蛋氨酸的质子化常数、15个稀土元素与该配体生成配合物的稳定常数。表明稀土与L-蛋氨酸可生成1:1配合物。讨论了“四分组效应”及钇的位置。用量热滴定法直接测定了稀土与L-蛋氨酸生成1:1配合物的△H_(101)值, 计算了△S_(101)和△G_(101)值。     

新型铈组稀土显色剂对乙酰基偶氮胂两类显色反应的研究

本文探讨了两类显色反应的特点和转化关系,并测定了两种络合物的组成。     

Étude par spectrométrie infra-rouge des complexes des terres rares avec l'oxyde de tri-n-butylphosphine á l'état solide

Tri-n-butylphosphine oxide (TBPO) reacts with rare earth nitrates to form complexes of general formula Me(NO₃)₃·3 TBPO. These complexes were studied by infrared spectrometry. The coordination of the nitrates is not the same along the lanthanide series. They are bidentate for the light rare earths and monodentate for the heavy earths. The P=O frequency does not vary monotonously when Z increases; there is a break for gadolinium. This is explained by an influence of backbonding, the decrease of the ionic radius and the coordination number.     

Magnetic Field Directed Rare‐Earth Separations

The separation of rare‐earth ions from one another is challenging due to their chemical and physical similarities. Nearly all rare‐earth separations rely upon small changes in ionic radii to direct speciation or reactivity. Herein, we show that the intrinsic magnetic properties of the rare‐earth ions impact the separations of light/heavy and selected heavy/heavy binary mixtures. Using TriNOx^3? ([{(2‐^tBuNO)C₆H₄CH₂}₃N]^3?) rare‐earth complexes, we efficiently and selectively crystallized heavy rare earths (Tb–Yb) from a mixture with light rare earths (La and Nd) in the presence of an external Fe₁₄Nd₂B magnet, concomitant with the introduction of a concentration gradient (decrease in temperature). The optimal separation was observed for an equimolar mixture of La:Dy, which gave an enrichment factor of EF_La:Dy=297±31 for the solid fraction, compared to EF_La:Dy=159±22 in the absence of the field, and achieving a 99.7 % pure Dy sample in one step. These results indicate that the application of a magnetic field can improve performance in a molecular separation system for paramagnetic rare‐earth cations.     

稀土-氨基J酸偶氮氯膦-氯代十四烷基吡啶-乙醇多元络合物的研究及分析应用

本文研究了氨基-J酸偶氮氯膦在阳离子表面活性剂存在下与稀土元素形成多元络合物的显色反应,并进行了实样分析。     

Solvent extraction of trivalent lanthanide Pr(III), Ho(III) and Er(III) with N-benzoyl-N-phenylhydroxylamine

Extraction of Pr(III), Ho(III) and Er(III) has been studied in the pH range of 1–10 with N-benzoyl-N-phenylhydroxylamine (BPHA) in benzene. The separation was found to be quantitative in borate media from pH 7 to 10, at an ionic strength of 0.1M (H⁺, BO₃ ^3–). The stoichiometric composition of the complexes under the optimal conditions of shaking time, pH and reagent concentration was formulated using slope analysis and found to be M(BPHA)₃, where M=Pr(III), Ho(III) and Er(III). The effect of various masking agents shows that citrate, ascorbate, EDTA, oxalate, fluoride and phosphate form stable complexes with these rare earths as compared to BPHA. The decontamination factors for different cations with respect to these rare earths under the optimum conditions have been evaluated.     

Stabilité dans le méthanol et propriétés thermodynamiques de transfert des cryptates de certains cations de transition et de métaux lourds

Stability in Methanol and Thermodynamic Transfer Properties of the Cryptates of some Transition Cations and Heavy Metals The nature and stability of the macrocyclic and macrobicyclic complexes of Ag⁺, Cd²⁺, and Pb²⁺ (Mⁿ⁺) with 21, 22, 211, 221 and 222 in anhydrous methanol 0.05M in Et₄N⁺ClO^?₄, at 25° (see Scheme) have been determined by potentiometry and spectrophotometry. Binuclear complexes M₂L²ⁿ⁺ have been observed in all cases, besides the mononuclear MLⁿ⁺ complexes. The macrobicyclic 1:1 complexes MLⁿ⁺ exhibit an important ‘cryptate effect’ with Mⁿ⁺=Ag⁺, Pb²⁺ and Cd²⁺, but not with Cu²⁺ and Zn²⁺; their stability is in all cases maximum with 221. The applicability to our results of the recent extrathermodynamic hypothesis involving MLⁿ⁺ cryptates is examined.     

Study on the cocolouration effect in the β-complex formation reactions of rare earths with p-chloro-chlorophosphonazo (CPApC)

Terbium- and yttrium-group rare earths form β-complexes with CPApC in acidic medium.The sensitivities for determination of these rare earths by this reaction depend on their ionic radii.Cerium- or terbium-group rare earth in the presence of yttrium-group element produces the cocolourationeffect which remarkably sensitizes the reaction. Yb-CPApC-Eu complex has a molar composition of1:4:2 and gives a molar absorptivity of 2. 02 ×10~5 L·mol~(-1)·cm~(-1) at 746 nm for Eu. It is found thatthe closer the lengths of ionic radii of the rare earths are, the greater will be the cocolouration effect.     

Separation of high purity gadolinium for reactor application by solvent extraction process

A solvent extraction process for the production of nuclear grade Gd₂O₃ for its applications in pressurized heavy water reactor (PHWR) from a crude concentrate of rare earths containing ~70 % Gd₂O₃ has been developed and tested on bench-scale and continuous counter-current operations. The separation of gadolinium from other rare earths with similar chemical properties has been successfully accomplished by adopting a dual cycle solvent extraction employing 2-ethylhexylphosphonic acid, mono-2 ethylhexyl ester (EHEHPA) as an extractant. Taking advantage of the extraction order of rare earths with EHEHPA, in the first cycle, heavy rare earths including Tb, Dy and Y were separated in the product strip solution, while gadolinium was separated in the raffinate solution along with samarium and neodymium. In the second cycle, gadolinium was purified to the extent of >99.5 % with respect to other rare earths. Effects of process variables such as aqueous acidity, phase ratio, metal concentration in the aqueous feed, scrubbing and stripping acidity etc. on separation of terbium and other heavy rare earths in the first cycle and upgrading the purity of Gd₂O₃ in the second cycle have been investigated. The experimental conditions were optimized using computer simulation and validated by bench scale counter-current operations. Under optimized conditions of process parameters, continuous operations of mixer settler yielded kilogram quantity of nuclear pure Gd₂O₃ which was subsequently converted to gadolinium nitrate for PHWR application. The overall recovery was found to be >98 %.     

Rare earth complexes with noncyclic polyether-methionine Schiff base

A novel Schiff base (TAMET) was synthesized by the condensation of tetraglycol aldehyde with methionine and a mild oxidant CrO3· (C5H5N)2 was selected for the reaction. Seven new rare earth complexes with this Schiff base have been synthesized and characterized by elemental analysis, TG-DTA, molar conductivity, magnetic susceptibility and IR, especially 1H NMR spectra. Information was obtained from reflectance spectra and the coordination of sulfur atom to rare earths was discussed. The experimental results show that thesecompounds have some biological activity and could dispose of O2.     

稀土组氨酸配合物的合成和性质研究

本文合成了十二个稀土与Ｌ－组氨酸（Ｌ－Ｈｉｓ）的固体配合物，元素分析结果表明配合物的组成为Ｌｎ（Ｈｉｓ）３（ＮＯ３）３２Ｈ２Ｏ（Ｌｎ＝Ｙ，Ｌａ，Ｃｅ，Ｐｒ，Ｎｄ，Ｓｍ，Ｅｕ，Ｇｄ，Ｔｂ，Ｄｙ，Ｅｒ，Ｔｍ）。并通过配合物的ＩＲ、ＵＶ、Ｈ－ＮＭＲ、ＴＧ－ＤＴＡ、磁化率及在水中的摩尔电导等的研究，表征了这些配合物的物理化学性质，结果表明稀土组氨配合物中配体通过羟基氧原子与镧系离子配位。     

Étude par spectroscopie d'absorption de la complexation des lanthanides trivalents par les acides amino-carboxyliques

An absorption spectrophotometric study of the complexation of trivalent lanthanides by aminocarboxylic acidsComplexation of the lanthanides by aminoacetic acids shows a shift in some absorption bands of the cation towards higher wavelengths. By choosing the medium —pH and concentrations —adequately, each complex species can be characterized by a certain shift. This study has been carried out at 20°C in M KCl and concerns the 1:1, 1:2, 1:3 and mixed complexes of praseodymium, holmium and thulium with G, NTA, HEDTA, EDTA, DCTA and DTPA. The characteristic shifts are correlated with the number of coordinating sites of the chelating agents. It seems that a significant change occurs in the structure of the complex when the number of coordinating sites exceeds nine for the cerium rare earths or eight for the yttrium elements.     

Nature et stabilité des complexes métalliques de cryptands dinucléants en solution II. Polythiamacrotricycles et monocycles apparentés

Nature and Stability of Some Metallic Complexes of Dinucleating Cryptands in Solution II. Polythiamacrotricycles and Related Monocyclic Subunits The stability constants of the Cu²⁺ and Ag⁺ complexes of the cylindrical macrotricycle 1a (1,7,13,19-tetraaza 4,16-dioxa 10,22,27,32-tetrathiatricyclo[17.5.5.5]tetratriacontane) have been determined by pH-metry, as well as those of the Cu²⁺, Co²⁺, Zn²⁺, Cd²⁺, Pb²⁺, and Ag⁺ complexes of the monocyclic subunit 2a (1,7-dimethyl-1,7-diaza 4,10-dithiacyclododecane), in aqueous solutions (NaClO₄) at 25°. In the Cu(II) systems, equilibria were reached slowly, and the results established by pH-metry were confirmed by UV/VIS spectrophotometric studies. The tricycle 1a forms dinuclear cryptates with copper and silver, with overall stability constants log β₂₁₀ (Cu₂- 1a )⁴⁺ = 18.5, log β_21-2 (Cu₂- 1a (OH)₂)²⁺ = 4.8, log β₂₁₀(Ag₂- 1a )²⁺ = 23.0. Ag⁺ also forms a mononuclear (Ag- 1a )⁺ complex, with log β₁₁₀ = 13.1, but no mononuclear species were detected in the Cu- 1a system. The absorption spectra of the bis-Cu(II) complexes of 1a and 2a in aqueous medium, MeOH and propylene carbonate (PC) are given, as well as those, in MeOH and PC, of the bis-copper complexes of the related monocycles 3 and 4 (1,7-diaza-4,10,13-trithiacyclopentadecane and 1.10-diaza 4,7,13,16-tetrathiacyclooctadecane, respectively), and tricycle 5 with two benzyl groups in the lateral chains. The complexing properties of the polyoxa- and polythia macrotricycles (Parts I and II of this series) are compared to those of other bis-chelating ligands, the bicyclic bis-tren and the monocyclic bis-dien.     

Separation and gravimetric determination of thorium and cerium(IV) with vanillin

Vanillin forms insoluble complexes with thorium and cerium(IV) at pH 4.0–6.2 and 2.5–7.0 respectively. Thorium and cerium can be determined gravimetrically and separated from each other as well as from uranium(VI) and typical trivalent rare earths. The precipitates obtained are ignited to the corresponding oxide and weighed; as little as 4.4 mg of ThO₂ and 4.9 mg of CeO₂ can be determined.     

新显色剂偶氮胂DBF分光光度法测定稀土元素研究

变色酸双偶氮胂类化合物是光度法测定稀土元素的重要显色剂,如偶氮胂Ⅲ、三溴偶氮胂等。为研究各种取代基对这类显色剂与稀土配合物的影响,将对甲基二溴偶氮胂中的甲基换为甲酰基,合成得偶氮胂DBF,化学命名为2-(2-胂酸基苯偶氮)-7-(2,6二溴-4-甲酰基苯偶氮)-1,8-二羟基萘-3,6-二磺酸。