Co-crystallization of octahedral and icosahedral fluoroanions in K3(AsF6)(B12F12) and Cs3(AsF6)(B12F12). Rare examples of salts containing fluoroanions with different shapes and charges

Crystals grown from anhydrous HF solutions of CsAsF₆ and Cs₂B₁₂F₁₂ or KAsF₆ and Cs₂B₁₂F₁₂ are shown by Raman spectroscopy and single-crystal X-ray diffraction to be the ternary salts K₃(AsF₆)(B₁₂F₁₂) or Cs₃(AsF₆)(B₁₂F₁₂). Both compounds exhibit a modified version of the anti-perovskite structure. They are rare examples of crystals that simultaneously contain octahedral and icosahedral molecular species and are also rare examples of salts containing fluoroanions with different shapes and charges. The crystallographic results show that both compounds are densely packed.     

Local structural analyses on molten terbium fluoride in lithium fluoride and lithium-calcium fluoride mixtures

X-ray absorption fine structure (XAFS) measurements on terbium fluoride in molten lithium fluoride and in molten lithium-calcium fluoride mixtures, (e.g. 0.20TbF₃-0.80LiF, 0.20TbF₃-0.62LiF-0.18CaF₂, 0.20TbF₃-0.48LiF-0.32CaF₂, 0.50TbF₃-0.50LiF, and 0.50TbF₃-0.38LiF-0.12CaF₂), have been carried out. In the solid state, coordination number of terbium (N_i) and inter ionic distances between terbium and fluorine in the first neighbor (r_i) are nearly constant in all mixtures. In 0.20TbF₃-0.80LiF, 0.20TbF₃-0.62LiF-0.18CaF₂ and 0.50TbF₃-0.50LiF mixtures, N_i's decrease from ca. 8 to 6 and r_i's also decrease from ca. 2.29 to 2.26 Å on melting. On the other hands, in molten 0.20TbF₃-0.48LiF-0.32CaF₂ and 0.50TbF₃-0.38LiF-0.12CaF₂ mixtures, N_i's are slightly larger than 6 and r_i's do not change. These facts correspond to the amount of F⁻ supplied by solvent melts, i.e. the effect of CaF₂ becomes predominant at bCaF₂ > 0.32 in ternary 0.20TbF₃-aLiF-bCaF₂ mixtures and at bCaF₂ > 0.12 in ternary 0.50TbF₃-aLiF-bCaF₂ mixtures.     

Electronic absorption spectra of U (III) ion in a LiCl–KCl eutectic melt at 450 °C

We have measured the electronic absorption spectra of the U(III) ion in LiCl–KCl eutectic melt at 450 °C to understand its chemical behavior in the context of pyrochemical process of spent nuclear fuel. The UV–VIS spectra of the U(III) ion consist of two main peaks in the range of 400–600 nm which are attributable to the 5f³–5f²6d¹ transitions. With the aid of UV–VIS spectroscopic tool, in-situ measurement of chemical reactions of the U(III) with oxide ion as well as neodymium oxide was successfully achieved. The U(III) ion forms insoluble uranium oxide phases by reacting with oxide ion and lanthanide oxides.     

Synthesis and luminescence properties of Yb and Er doped KLa(WO4)2 nanoparticles

The luminescent nanocrystalline Yb³⁺ and Er³⁺ codoped KLa(WO₄)₂ has been prepared by Pechini method. X-ray diffraction and transmission electron microscope were used to study the structure of the obtained samples. The average grain size of these samples depended on the annealing temperature, increasing with the increase of the temperature. The cell parameters and the crystallite size of KYb_xEr_0.02La_0.98−x(WO₄)₂ nanocrystalline decreased with the increase of x value. Luminescence studies showed that the intensity of upconversion emission of the Yb³⁺ and Er³⁺ codoped samples was much stronger than that of the Er³⁺ single doped samples (pumped by 980 nm LD). The upconversion emission mechanisms suggested that all the three bands of upconversion emissions were two-photon process.     

Headspace solid-phase microextraction combined with comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry for the determination of volatile compounds from marine salt

In this work, a methodology to characterise the volatile and semi-volatile compounds from marine salt by headspace solid-phase microextraction (HS-SPME) and comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC × GC/TOFMS) was developed. Samples from two saltpans of Aveiro, in Portugal, with diverse locations, obtained over three years (2004, 2005, and 2007) were analysed. A 50/30 μm divinylbenzene/carboxen/polydimethylsiloxane SPME fibre was used. The volatiles present in the headspace of the solid salt samples (crystals) were equilibrated overnight at 60 °C and extracted for 60 min prior to injection in the GC × GC/TOFMS. 157 compounds, distributed over the chemical groups of hydrocarbons, aldehydes, esters, furans, haloalkanes, ketones, ethers, alcohols, terpenoids, C₁₃ norisoprenoids, and lactones were detected across the samples. Furans, haloalkanes and ethers were identified for the first time in marine salt. The large number of co-elutions on the first column that were resolved by the GC × GC system revealed the complexity of marine salt volatile composition. The existence of a structured 2D chromatographic behaviour according to volatility, in the first dimension (¹D), and primarily polarity, in the second dimension (²D), was demonstrated, allowing more reliable identifications. The resolution and sensitivity of GC × GC/TOFMS enabled the separation and identification of a higher number of volatile compounds compared to GC–qMS, allowing a deeper characterisation of this natural product.     

Speciation analysis of aluminium and aluminium fluoride complexes by HPIC-UVVIS

The study presents a new analytical method for speciation analysis in fractionation of aluminium fluoride complexes and free Al³⁺ in soil samples. Aluminium speciation was studied in model solutions and soil extract samples by means of high performance ion chromatography (HPIC) with UV-VIS detection using post-column reaction with tiron for the separation and detection of aluminium fluoride complex and Al³⁺ forms during one analysis. The paper presents particular stages of the chromatographic process optimization involving selecting the appropriate eluent strength, type of elution or concentration and quantity of derivatization reagent. HPIC was performed on a bifunctional analytical column Dionex IonPac CS5A. The use of gradient elution and the eluents A: 1 M NH₄Cl and B: water acidified to pH of eluent phase, enabled full separation of fluoride aluminium forms as AlF₂⁺, AlF₃⁰, AlF₄⁻ (first signal), AlF²⁺ (second signal) and form Al³⁺ in a single analytical procedure. The proposed new method HPIC-UVVIS was applied successfully in the quantitative and qualitative analysis of soil samples.     

Synthesis of zwitterionic salts via three component reactions of nitrogen-containing heterocycles, acetylenedicarboxylate and cyclic 1,3-dicarbonyl compounds

A practical synthetic procedure for the preparation of the charge-separated pyridinium-Meldrum acid zwitterionic salts was developed through a unique one-pot three component reaction of pyridine, acetylenedicarboxylate and Meldrum acid. Other nitrogen-containing heterocycles such as N-methylimidazole, 2-picoline, quinoline, isoquinoline and other cyclic 1,3-dicarbonyl compounds such as 1,3-cyclopentanedione, 1,3-cyclohexanedione, barbituric acid also took part in the reaction to give corresponding zwitterionic salts in moderate yields, respectively. In one case an unusual isoquinolinium 1,3-cyclopentanedionate was obtained. A feasible explanation is given for this novel one-pot tandem reaction and the formation of different kinds of products.     

亚甲基蒽苯乙烯吡啶盐的合成、结构及双光子吸收性质

以氯化4-甲基-N-9-亚甲基蒽吡啶盐为原料,合成了一种新型的苯乙烯吡啶盐,通过红外、核磁共振氢谱、碳谱、电喷雾质谱、单晶X射线衍射等测试技术对化合物的结构进行了表征。单晶X射线衍射结果表明,该化合物属于单斜晶系,空间群为P21/c,晶胞参数a=1.255 7(1)nm,b=1.539(1)nm,c=2.220 2(8)nm,β=101.099(1)°,V=4.210 5(4)nm3,Z=4,Dc=1.159 g/cm3。用1 064 nm皮秒脉冲激光研究其三阶非线性光学特性,双光子吸收系数β=0.028 cm/GW,吸收截面为σ=8.68×10-48cm4.s.photon-1,表明目标化合物具有良好的三阶非线性光学性质。     

水相中3,5-二芳基异噁唑衍生物的微波辐射合成

微波辐射下,以芳香醛和芳香酮为起始原料合成2,4,6-三芳基吡喃盐,在NaOH水溶液中与盐酸羟胺发生开环、缩环和脱苯甲酰基反应,一步生成3,5-二芳基异噁唑衍生物。考察了微波辐射功率和辐射时间对目标产物收率的影响,2,4,6-三芳基吡喃盐与盐酸羟胺反应生成3,5-二芳基异噁唑衍生物的最佳微波辐射功率为600W,辐射时间为8min,最大收率为83%。该法不仅避免了使用高氯酸造成的环境污染,而且以水作为反应介质,使后处理简便。该工艺具有操作安全、反应条件温和和产率高等优点,是一种环境友好的合成工艺。产物经元素分析、1HNMR和MS测试技术表征了其结构。