Crystal chemistry of lanthanide oxochlorotungstates

Crystal chemical properties of lanthanide oxochlorotungstates of composition LnWO₄Cl (Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm) are reported. The unit cell parameters a, b, c, c′, and V of the LnWO₄Cl compounds are correlated with lanthanide ionic radii from different radius systems and with the lanthanide atomic number. The ionic radius systems most suitable for describing the crystal chemical properties of the lanthanide oxochlorotungstates are determined.     

镧系元素光化学 III: 铕的光还原分离

本文报道了以低压汞灯做光源, HCO2H-HCO2Na做自由基清除剂, Na2SO4做光还原产物Eu(II)的沉淀剂, 在改变自由基清除剂、沉淀剂和稀土离子浓度、溶液的酸度和光强度的条件下, 研究了从铕和其它镧系元素氯化物的二元混合物中光还原分离提取铕的问题, 同时测定了沉淀的组成以及元素间的分离因数(β)。     

Quantum chemistry benchmarking of binding and selectivity for lanthanide extractants

Computer‐aided screening methods facilitate the discovery of new extractants for heavy and rare‐earth metal separations. In this work, we have benchmarked the accuracy of different quantum chemistry methods for calculating extractant binding energies and selectivities. Specifically, we compare calculated data from different exchange correlation functionals (B3LYP‐D3, ωB97X‐D3, and M06‐L) and different basis sets (including large‐core effective core potentials and all‐electron basis sets). We report aqueous‐phase binding energy and selectivity trends for 1:1 and 3:1 extractant/lanthanide models for the complexes. We find that binding selectivities are not particularly sensitive to model chemistry, but binding energies are sensitive. Furthermore, calculated trends in selectivity using 3:1 extractant/lanthanide models are in better agreement with available experimental trends than trends using 1:1 extractant/lanthanide models. Lastly, we find that the B3LYP‐D3/6‐31 + G* model chemistry with the Stuttgart large‐core relativistic effective core potentials on the lanthanide sufficiently reproduces results from larger basis set calculations and is confirmed as suitable for relatively fast and efficient screening of lanthanide binding energies and selectivities.     

Investigation of desolvation process in lanthanide dinicotinates

The desolvation process in lanthanide pyridine-3,5-dicarboxylates of the formulae [Tb₂pdc₃(dmf)₂]·dmf (1), [Ho₂pdc₃(dmf)₂]·dmf (2), [Erdc₃(dmf)₂]·dmf (3), and [Yb₂pdc₃(dmf)₂]·dmf (4) where pdc-C₅H₃N(COO)₂²⁻, dmf-N,N′-dimethylformamide) has been investigated by means of the TG–DSC, TG–FTIR, IR and XRD methods. Heating of the complexes in the range 30–260 °C lead to evolution of weakly bonded dmf molecules included in the channels as well those directly bonded with lanthanide atoms. The kinetic analysis revealed a multistep desolvation pattern.     

Crystal chemistry of orthorhombic lanthanide oxobromotungstates of composition LnWO4Br

The crystal-chemical properties of lanthanide oxobromotungstates of composition LnWO₄Br(Ln = La, Pr, Nd, Sm) were studied: the crystal system and space group were determined, and the unit cell parameters were refined. The dependence of the unit cell parameters a, b, c, and V of the LnWO₄Br compounds on the lanthanide atomic number was analyzed. The analytical equations derived make it possible to predict the unit cell parameters for lanthanide oxobromotungstates that have not been synthesized yet.     

Flame-ion chemistry of the lanthanide metals Ce,Pr and Nd

A pair of premixed, H₂O₂Ar flames of fuel-rich (FR) and fuel-lean (FL) composition, both at atmospheric pressure and 2425 K, were doped with about 10⁻⁶ mol fraction of the lanthanide metals La, Ce, Pr and Nd; from a previous study, La was used as a benchmark. The metals produce solid particles in the flames and gaseous metallic species. The latter include metallic atoms A near the flame reaction zone, but only the monoxide AO, the oxide hydroxide OAOH and, in some cases, the dioxide AO₂ further downstream at equilibrium. Metallic ions (< 1% of the total metal) were observed by sampling the flames through a nozzle into a mass spectrometer. All of the observed ions can be represented by four hydrate series: (a) major signals of AO⁺·nH₂O (n = 0–3) for La, Ce, Pr and Nd; (b) small signals of AO₂H⁺·nH₂O (n = 0–2) for Ce, Pr and Nd; (c) still smaller signals of AO₂⁺·nH₂O (n = 0, 1) for Ce, Pr and Nd in the FL flame only; and (d) tiny signals of AOH⁺·nH₂O (n = 0, 1) for Pr and Nd in the FR flame only. The actual structures of some of these ions may not correspond to simple hydrates: e.g. AO⁺·H₂O = A(OH)₂⁺ = protonated OAOH; AO₂H⁺·H₂O = A(OH)₃⁺, etc. Since hydrogen flames contain essentially no natural ionization, a major objective was to consider probable ionization mechanisms for the metals. The primary reactions include both chemi-ionization, and thermal (collisional) ionization of AO whose ionization energy is low (about 5 eV). Some of the ions are formed by secondary ion/molecule reactions including three-body hydration, proton transfer, electron (charge) transfer, H atom abstraction by radicals and oxidation. In addition, the chemical ionization of the metallic species by H₃O⁺ was investigated. The flame-ion chemistry of these metals is discussed in detail.     

Calixarenes in analytical and separation chemistry

Discovered in the 1940’s, [1_n]metacyclophanes with the common name calix[n]arenes which is derived from for the molecule’s shape enjoyed a remarkable interest in almost all fields of chemistry since the 1980’s, which is highlighted by several books [1–8]. Over 50 reviews concerning their synthesis, properties and applicabilities were published, many of those with emphasis on organic synthesis and structural properties are cited in ¶[P. 5–6 in 2]. Of interest for analytical chemists are reviews on calixarenes and the structurally related resorcin[n]arenes (or calix[n]resorcarenes) and calixpyrroles concerning potentiometric sensors [9–12], chromo- and fluorophores [13, 14], molecular switches [15], metal ion binding in solution [16–19], redox properties [20] and anion binding [21–24]. Other recent reviews deal with thermodynamic aspects [25], organometallic compounds [26], P-containing calixarenes [27–29], as well as molecular dynamics modeling [30–33]. It is a vital field with over 200 publications per year. Therefore, this article presents only selected results on complexation, solvent extraction and membrane transport with the emphasis on ion and molecular recognition which can be used for analytical purposes, without attempting to cover all available references.     

Calixarenes in analytical and separation chemistry

Discovered in the 1940's, [1n]metacyclophanes with the common name calix[n]arenes which is derived from for the molecule's shape enjoyed a remarkable interest in almost all fields of chemistry since the 1980's, which is highlighted by several books [1-8]. Over 50 reviews concerning their synthesis, properties and applicabilities were published, many of those with emphasis on organic synthesis and structural properties are cited in [P. 5-6 in 2]. Of interest for analytical chemists are reviews on calixarenes and the structurally related resorcin[n]arenes (or calix[n]resorcarenes) and calixpyrroles concerning potentiometric sensors [9-12], chromo- and fluorophores [13, 14], molecular switches [15], metal ion binding in solution [16-19], redox properties [20] and anion binding [21-24]. Other recent reviews deal with thermodynamic aspects [25], organometallic compounds [26], P-containing calixarenes [27-29], as well as molecular dynamics modeling [30-33]. It is a vital field with over 200 publications per year. Therefore, this article presents only selected results on complexation, solvent extraction and membrane transport with the emphasis on ion and molecular recognition which can be used for analytical purposes, without attempting to cover all available references.     

Rapid separation of beryllium and lanthanide derivatives by capillary gas chromatography

Previous studies describe derivatization of metal ions followed by analysis using gas chromatography, usually on packed columns. In many of these studies, stable and volatile derivatives were formed using fluorinated β‐diketonate reagents. This paper extends previous work by investigating separations of the derivatives on small‐diameter capillary gas chromatography columns and exploring on‐fiber, solid‐phase microextraction derivatization techniques for beryllium. The β‐diketonate used for these studies was 1,1,1,2,2,6,6,7,7,7‐decafluoro‐3,5‐heptanedione. Derivatization of lanthanides also required addition of a neutral donor, dibutyl sulfoxide, in addition to 1,1,1,2,2,6,6,7,7,7‐decafluoro‐3,5‐heptanedione. Unoptimized separations on a 100‐μm i.d. capillary column proved capable of rapid separations (within 15 min) of lanthanide derivatives that are adjacent to one another in the periodic table. Full‐scan mass spectra were obtained from derivatives containing 5 ng of each lanthanide. Studies also developed a simple on‐fiber solid‐phase microextraction derivatization of beryllium. Beryllium could be analyzed in the presence of other alkali earth elements (Ba(II) and Sr(II)) without interference. Extension of the general approach was demonstrated for several additional elements (i.e. Cu(II), Cr(III), and Ga(III)).     

HPLC separation of heterocyclic beta-diketonates of actinide, lanthanide and transition metals

Liquid-chromatography conditions for the separation of neutral chelates of 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone with transition metals, lanthanides and actinides have been established. The use of reverse-phase liquid chromatography, instead of ion-exchange, is a novel approach for actinide separation. The high molar absorptivities of the beta-diketonates in the ultraviolet region allow for their detection at the nanogram level. The potential exists, therefore, for the rapid solvent extraction, concentration and determination of traces of actinides and other metals.     

Supramolecular coordination chemistry in aqueous solution: lanthanide ion-induced triple helix formation

The self-assembly of dinuclear triple helical lanthanide ion complexes (helicates), in aqueous solution, is investigated utilizing laser-induced, lanthanide luminescence spectroscopy. A series of dinuclear lanthanide (III) helicates (Ln(III)) based on 2,6-pyridinedicarboxylic acid (dipicolinic acid, dpa) coordinating units was synthesized by linking two dpa moieties using the organic diamines (1R,2R)-diaminocyclohexane (chxn-R,R) and 4,4'-diaminodiphenylmethane (dpm). Luminescence excitation spectroscopy of the Eu3+ 7F0-->5D0 transition shows the apparent cooperative formation of neutral triple helical complexes in aqueous solution, with a [Eu2L3] stoichiometry. Eu3+ excitation peak wavelengths and excited-state lifetimes correspond to those of the [Eu(dpa)3]3- model complex. CD studies of the Nd(III) helicate Nd2(dpa-chxn-R,R)3 reveal optical activity of the f-f transitions, indicating that the chiral linking group induces a stable chirality at the metal ion center. Molecular mechanics calculations using CHARMm suggest that the delta delta configuration at the Nd3+ ion centers is induced by the chxn-R,R linker. Stability constants were determined for both ligands with Eu3+, yielding identical results: log K = 31.6 +/- 0.2 (K in units of M-4). Metal-metal distances calculated from Eu3+-->Nd3+ energy-transfer experiments show that the complexes have metal-metal distances close to those calculated by molecular modeling. The fine structure in the Tb3+ emission bands is consistent with the approximate D3 symmetry as anticipated for helicates.     

Investigation of the chemistry of heterocycles

The reaction of ethoxalylanthranil with aryl(heteryl)amines was studied, a method for obtaining 2-carbethoxy-3-R-substituted 4-quinazolones was developed, and the transformations of the latter were investigated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1575–1578, November, 1970.     

Investigation of the chemistry of phenoxazines

Depending on the position of the annelated benzene ring, benzophenoxazinones add thiophenols in the benzenoid, quinonoid, or both parts of the molecule to give mono- or diarylmercapto derivatives. A substituent in the benzenoid portion of the molecule hinders polarographic reduction and shifts the visible absorption band bathochromically, while a substituent in the quinonoid portion has practically no effect on the E_1/2 value.See [1] for communication IV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1345–1350, October, 1972     

Investigation of the chemistry of phenylpyridines

Amination of 2-phenylpyridine under the conditions of the Chichibabin reaction gave 6-amino-2-phenylpyridine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1642–1643, December, 1972.     

Colloid chemistry principles of separation of pure alkyl sulfates

Sodium dodecyl sulfate and other alkyl sulfates were treated by the method of polythermal conductometry to remove primary alcohols. The electrical conductivity polytherms were analyzed. The composition of the liquid and solid phases in equilibrium in the mixed solutions was determined. The method of the synthesis of chemical purity colloids of alkyl sulfates and other ionogenic micelle forming surfactants was suggested based on the optimal choice of crystallization temperature of the solutions.     

Relationship between the solubilities and separation factors for the co-crystallization of lanthanide ethylsulphates

Co-crystallization coefficients of lanthanide ethylsulphates [Ln(H₂O)₉] (C₂H₅SO₄)₃ were determined and compared with the solubility of these salts. In contrast to the common opinion denying any simple correlation between co-crystallization coefficients and solubilities it was established that a simple relationship does exist for ethylsulphates of light lanthanides. It was concluded that in the case of light lanthanides an almost complete compesation of activity coefficients in the RATNER equation is due to the similar structure of the hydrated cations [Ln(H₂O)₉]³⁺ in both the solid and the aqueous phase. For ethylsulphates of heavy lanthanides such a compensation was not observed, since in this case the cations in the aqueous phase are probably hydrated by 8 water molecules, while in the solid phase the coordination number is still 9. The solubility of Pm, Pu, Am and Cm ethylsulphates was determined by the method “from matrix”. Presented in part at the Italian-Polish Meeting on the Properties and the Development of Methods for Separating Lanthanide Fission Products and Transuranian Elements in Post-Irradiation Analysis of Nuclear Fuels, held in Rome, 19–26 November 1974.