Antiferromagnetic Alkali Metal Oxohydroxoferrates(III) with Correlated Hydrogen Bonding Systems

The oxohydroxoferrates(III) A₂[Fe₂O₃(OH)₂] (A=K, Rb, Cs) were synthesized under hydroflux conditions. Approximately equimolar mixtures of the alkali metal hydroxides and water were reacted with Fe(NO₃)₃ ⋅ 9H₂O at about 200 °C. The product formation depends on the hydroxide concentration, therefore also other reaction products, such as KFeO₂, K_2−x[Fe₄O_7−x(OH)_x] or α-Fe₂O₃, are obtained. The crystal structures of the oxohydroxoferrates(III) A₂[Fe₂O₃(OH)₂] follow the same structural principle, yet differ in their layer stacking or/and their hydrogen bonding systems depending on A and temperature. In the resulting four different orthorhombic structure types, [FeO₃OH]⁴⁻ tetrahedra share their oxide corners to create folded Fe₂O₃(OH)₂]²⁻ layers. The terminal hydroxide ligands form hydrogen bonds between and/or within the layers. The positions of the hydrogen atoms in these networks are correlated. The A⁺ cations are located between the folded anionic layers as well as in their trenches. Under reaction conditions, the potassium compound crystallizes in the space group Cmce (Pearson symbol oC88), showing a bimodal disorder of the hydrogen atoms in hydrogen bridges. In a virtually hysteresis-less first-order transition at 340(2) K, the structure slightly distorts into the room-temperature modification with the subgroup Pbca (oP88), and the hydrogen atoms order. The rubidium and caesium compounds are isostructural to each other but not to the potassium compound, and are always obtained as mixtures of two modifications with space groups Cmce (oC88′) and Immb (oI88). Upon heating, the oxohydroxoferrates decompose into their anhydrides AFeO₂ and water. The type of hydrogen bonding network influences the decomposition temperature, the structure and the morphology of the crystals. Despite the presence of iron(III), which was confirmed by ⁵⁷Fe-Mössbauer spectroscopy, K₂[Fe₂O₃(OH)₂] is diamagnetic in the investigated temperature range between 1.8 and 300 K. Neutron diffraction revealed strong antiferromagnetic coupling of the magnetic moments, which are inverted in neighboring tetrahedra.     

Fast Sodium‐Ion Conductivity in Supertetrahedral Phosphidosilicates

Fast sodium‐ion conductors are key components of Na‐based all‐solid‐state batteries which hold promise for large‐scale storage of electrical power. We report the synthesis, crystal‐structure determination, and Na⁺‐ion conductivities of six new Na‐ion conductors, the phosphidosilicates Na₁₉Si₁₃P₂₅, Na₂₃Si₁₉P₃₃, Na₂₃Si₂₈P₄₅, Na₂₃Si₃₇P₅₇, LT‐NaSi₂P₃ and HT‐NaSi₂P₃, based entirely on earth‐abundant elements. They have SiP₄ tetrahedra assembled interpenetrating networks of T3 to T5 supertetrahedral clusters and can be hierarchically assigned to sphalerite‐ or diamond‐type structures. ²³Na solid‐state NMR spectra and geometrical pathway analysis show Na⁺‐ion mobility between the supertetrahedral cluster networks. Electrochemical impedance spectroscopy shows Na⁺‐ion conductivities up to σ (Na⁺)=4×10^?4 S cm^?1. The conductivities increase with the size of the supertetrahedral clusters through dilution of Na⁺‐ions as the charge density of the anionic networks decreases.     

利用压电频移法测定水中的痕量亚硝酸盐

提出了利用压电频移法测定亚硝酸盐的方法。方法以碘离子与亚硝酸根之间的氧化还原反应为依据，通过测定由反应生成的碘所引起的压电晶体频率的变化，在被萃取水相中亚硝酸盐浓度为０．００９￣２．３ｍｇ／Ｌ范围内，频移值与浓度成正比：ΔＦ＝５．８＋２．５×１０＾３Ｃ（ｍｇ／Ｌ），ｒ＝０．９９０１。方法简便，用于天然水中亚硝酸盐的测定，结果令人满意。     

锂离子电池正极材料的晶体结构及电化学性能

正极材料是锂离子电池的重要组成部分。作为提供自由脱嵌锂离子的正极材料,其晶体结构的特点决定了锂离子脱嵌路径方式的不同,并对锂离子电池的电化学性能等产生明显影响。本文根据正极材料的晶体结构和锂离子“脱嵌/嵌入”路径方式的不同,重点讨论了一维隧道结构、二维层状结构和三维框架结构正极材料的晶体结构特点、锂离子“脱嵌/嵌入”路径和其电化学性能之间的关系,主要包括一维隧道结构正极材料LiFePO₄,二维层状结构正极材料LiMO₂(M=Co, Ni, Mn)、Li_1+xV₃O₈和Li₂MSiO₄ (M=Fe, Mn) 以及三维框架结构正极材料LiMn₂O₄和Li₃V₂(PO₄)₃。揭示了目前锂离子电池正极材料的研究现状和存在问题,并对今后的发展方向进行了评述。     

New Reactivity of the Uranyl(VI) Ion

The chemistry of the uranyl ion ([UO₂]²⁺) has evolved remarkably over the past few years, with unexpected reactivity observed that challenge our understanding of this ion, and of actinides in general. This review highlights some recent advances in the field, focussing on the organometallic chemistry of the uranyl moiety, which is not well developed in comparison to lower oxidation states of uranium. The use of uranyl as a catalyst is highlighted and the newly developed supramolecular chemistry is described. The uranyl oxygen atoms have been considered as inert, but recent work has shown that is not necessarily the case and is discussed herein. Finally, reduction to the [UO₂]⁺ ion will be discussed.     

离子液体中卤素离子杂质的离子色谱-直接电导检测法分析

研究了离子色谱-直接电导检测法分离测定离子液体中的卤素离子(F~-、Cl~-、Br~-)杂质.采用Shim-pack IC-A3阴离子交换色谱柱,考察了淋洗液种类及浓度、流速和色谱柱温度对分离测定的影响.最佳色谱条件为:以1.25 mmol/L邻苯二甲酸氢钾为淋洗液,流速1.5 mL/min,色谱柱温45 ℃.在此条件下可以基线分离卤素离子,且NO~-_3、BF~-_4、SO~(2-)_4不干扰测定.该法测定卤素离子的检出限(S/N=3)为0.02 ～0.11 mg/L,峰面积的相对标准偏差(n=5)不大于0.7%,F~-、Cl~- 和Br~- 的标准曲线的线性范围分别为0.1 ～50、0.1 ～50、0.5 ～100 mg/L.将方法用于烷基咪唑四氟硼酸盐离子液体中卤素离子杂质的测定,加标回收率为98% ～102%.     

Ternäre Halogenide vom Typ A3MX6. III [1, 2]. Synthese,Strukturen und Ionenleitfähigkeit der Halogenide Na3MX6 (X = Cl,Br)

Ternary Halides of the A₃MX₆ Type. III [1, 2]. Synthesis, Structures, and Ionic Conductivity of the Halides Na₃MX₆ (X = Cl, Br) The bromides Na₃MBr₆ crystallize with the stuffed LiSbF₆-type structure (type I; M = Sm? Gd) or with the structure of the mineral cryolite (type II; M = Gd? Lu). The structure types were refined from single crystal X-ray data (Na₃SmBr₆: trigonal, space group R3 , a = 740.8(2) pm, c = 1 998.9(8) pm, Z = 3; Na₃YBr₆: monoclinic, space group P2₁/n, a = 721.3(4) pm, b = 769.9(2) pm, c = 1 074.8(4) pm, β = 90.60(4)°, Z = 2). Reversible phase transitions from one structure to the other occur. The phase transition temperatures were determined for the bromides as well as for the chlorides Na₃MCl₆ (M = Eu? Lu). The refinement of both structures for one compound was possible for Na₃GdBr₆ (I: trigonal, space group R3 , a = 737.1(5) pm, c = 1 887(2) pm, Z = 3; II: monoclinic, space group P2₁/n, a = 725.2(1) pm, b = 774.1(3) pm, c = 1 080.1(3) pm, β = 90.76(3)°, Z = 2). All compounds exhibit ionic conductivity of the sodium ions which decreases with the change from type I to type II. The conductivity of the bromides is always higher when compared with the respective chlorides.     

稀土双(11-钨硅酸)钾的质子导电性研究(英)

研究了K13［Ln（SiW11O39）2］nH2O（Ln=La，Ce，Pr，Nd，Sm，Gd）的质子导电性研究表明其导电性不仅与物质本性有关，也与外界条件如温度、频率等有关，不同结构的杂多化合物给出不同结构的质子导电性．总结了质子导电性随温度、结晶水数目、频率的变化总趋势．基于实验数据得出一些重要结论，所得数据未见文献报道．     

Synthesis, Structure and Conductivity of the New Charge-transfer Salt (ET)_2(CH_2=CH-CH_2-SO_3)·H_2O

ET is one of the most famous electron-donor molecules, which forms charge-transfer complexes (abbr. CT-complexes) with various types of counterions. These complexes have received intense attention because a wide range of physical properties such as conductivity and superconductivity1, ferromagnetism2-4 and nonlinear optical properties5 was found in these materials. Although the majority of the ET-based CT-complexes were prepared by combining with inorganic counterions, CT-complexes with o…     

The First Molybdenum(VI) and Tungsten(VI) Oxoazides MO2(N3)2, MO2(N3)2⋅2 CH3CN, (bipy)MO2(N3)2, and [MO2(N3)4]2− (M=Mo,W)

Molybdenum(VI) and tungsten(VI) dioxodiazide, MO₂(N₃)₂ (M=Mo, W), were prepared through fluoride–azide exchange reactions between MO₂F₂ and Me₃SiN₃ in SO₂ solution. In acetonitrile solution, the fluoride–azide exchange resulted in the isolation of the adducts MO₂(N₃)₂⋅2 CH₃CN. The subsequent reaction of MO₂(N₃)₂ with 2,2′‐bipyridine (bipy) gave the bipyridine adducts (bipy)MO₂(N₃)₂. The hydrolysis of (bipy)MoO₂(N₃)₂ resulted in the formation and isolation of [(bipy)MoO₂N₃]₂O. The tetraazido anions [MO₂(N₃)₄]²⁻ were obtained by the reaction of MO₂(N₃)₂ with two equivalents of ionic azide. Most molybdenum(VI) and tungsten(VI) dioxoazides were fully characterized by their vibrational spectra, impact, friction, and thermal sensitivity data and, in the case of (bipy)MoO₂(N₃)₂, (bipy)WO₂(N₃)₂, [PPh₄]₂[MoO₂(N₃)₄], [PPh₄]₂[WO₂(N₃)₄], and [(bipy)MoO₂N₃]₂O by their X‐ray crystal structures.     

New Solids in As-O-Mo,As(P)-O-Mo(W) and As(P)-O-Nb(W) Systems That Exhibit Nonlinear Optical Properties

Interactions between well-mixed fine powders of As₂O₃, P₂O₅, MoO₃, WO₃ and Nb₂O₅ at different stoichiometry in quartz ampoules under vacuum at ~1000 °C in the presence of metallic molybdenum (or niobium), over several weeks, led to shiny dichroic crystalline materials being formed in cooler parts of the reaction vessel. An addition of small quantities of metals-Mo or Nb-was made with the aim of partially reducing their highly oxidized Mo(VI), W(VI) or Nb(V) species to corresponding Mo(V), W(V) and Nb(IV) centers, in order to form mixed valence solids. Sublimed crystals of four new compounds were investigated using a variety of techniques, with prime emphasis on the X-ray analysis, followed by spectroscopy (diffusion reflectance, IR, Raman and EPR), second harmonic generation (SHG), thermal analysis under N₂ and air atmosphere, and single crystals electrical conductivity studies. The results evidenced the formation of new complex solids of previously unknown compositions and structures. Three out of four compounds crystallized in non-centrosymmetric space groups and represent layered 2D polymeric puckered structures that being stacked on each other form 3D lattices. All new solids exhibit strong second-harmonic-generation (SHG effect; based on YAG 1064 nm tests with detection of 532 nm photons), and a rare photosalient effect when crystals physically move in the laser beam. Single crystals’ electrical conductivity of the four new synthesized compounds was measured, and the results showed their semiconductor behavior. Values of band gaps of these new solids were determined using diffusion reflectance spectroscopy in the visible region. Aspects of new solids’ practical usefulness are discussed.     

Ion association in solutions of dimethylthallium(III) hydroxide

From studies of the specific hydroxide ion catalyzed decomposition of diacetone alcohol by dimethylthallium(III) hydroxide at 25°C, it is concluded that both ion pairs (dissociation constantK=0.090 mole-dm^–3) and dimers (dimerization constantK _d=1.5 dm³-mole^–1) exist in aqueous solution.Request for reprints should be addressed to: Dr. A. D. Pethybridge, Department of Chemistry, The University, Whiteknights Park, Reading, Berkshire, England.Deceased October 16, 1972.     

基于离子色谱/电导检测的全脂奶粉中硫氰酸盐污染物的测定及前处理方法研究

建立了氢氧根淋洗/离子色谱/电导检测分析全脂奶粉中硫氰酸盐（SCN-）污染物的分析方法,对蛋白沉淀剂、提取条件、提取液净化技术、色谱条件等作了深入研究和优化。通过对淋洗液梯度的优化,将出峰时间控制在17 min内,且不受邻近组分干扰。方法在0.02~100 mg/L范围内具有良好的线性关系,相关系数（r）为0.999 9,方法定量下限（S/N=10）为0.3 μg/g,回收率为99%~102%。方法重现性好,3 d内对2.0 mg/L的标准溶液随机测试7次,其峰面积的相对标准偏差（RSD）为1.6%。     

Synthesis, Spectroscopic Properties and Structural Characterization of Sodium Potassium Citrato Oxotungstate(VI) Dimer

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氯化物熔体中镱离子在铁电极上的电还原

The line scanning voltammetry was used to study the electrochemical reaction of Yb(Ⅲ) in NaCl-KCl equimolar mixture on the Fe cathode. It was found that the reduction of Yb(Ⅲ) to yb(Ⅱ ) was realized on Fe electrode in the first step. Yb(Ⅱ ) was then reduced and formed alloys with Fe. The diffusion coefficients of Yb(Ⅲ) and Yb(Ⅱ ) in NaCl-KCl were determined to be 2.0× 10-5cm2. s- 1 and l .1 × 10-5cm2's- 1 at 760 ℃, respectively. The diffusion activation energy of Yb(Ⅲ ) was 66.0kJ•mol-1.     

Cr(III) and Cr(VI) speciation measurements in environmental reference materials

The production of reference materials for quality control of Cr(III) and Cr(VI) speciation in environmental samples is described. It concerns in the first place two lyophilized solutions containing Cr(III) and Cr(VI) at different concentrations, respectively representative for drinking water and filter leaching solutions, and in the second place filters loaded with welding dust. Twenty-four laboratories with experience in the field participated in an intercomparison exercise organized to validate the suitability of the reference materials and to gauge the state-of-the-art of Cr speciation throughout Europe. The outcome of this exercise is discussed.     

Aerobic oxidation of tetrahydrofuran by a series of iron (III) containing POSS compounds

A series of iron (III) containing POSS compounds, [Bu₄N][(R)₇Si₇O₁₂FeCl] (R = isobutyl- (1), ethyl- (2), phenyl- (3), and cyclopentyl- (4)) were investigated as potential catalysts for aerobic oxidation of tetrahydrofuran (THF). The oxidation products for this reaction were characterized by IR, GC and GC–MS. The major oxidation product was γ-butyrolactone (C₄H₆O₂, GBL); while the two minor products were 2-hydroxy-THF and its tautomer, 4-hydroxybutanal. A third minor oxidative product is believed to be an isomer of dihydroxy-THF. THF free syntheses of 2–4 have been developed and all three compounds were characterized by elemental analysis, IR, and X-ray diffraction studies. The crystallographic data for 1–4 demonstrate a similar iron coordination sphere between the four compounds, but the different substitutents on the various POSS. The corresponding turnover numbers for the aerobic oxidation of THF suggest that smaller substitutents on the POSS ligands improve the stability of the catalytic species. When compared to other published catalytic iron systems, these turnover numbers appear to be the largest for the aerobic conversion of THF to GBL.     

Interaction of Thulium,Ytterbium(III) and Lutetium Chlorides with Sodium Chloride

The pseudobinary systems NaCl—LnCl₃ (Ln=Tm, Yb, Lu) were investigated by DTA and X-ray diffraction. Two types of ternary chlorides exist: congruently melting compounds Na₃LnCl₆ with the cryolite-structure, incongruently melting compounds NaLnCl₄ with the NaErCl₄-Ln (Ln=Tm) or the NaLnCl₄-structure (Ln=Yb, Lu). All these structure types contain [LnCl₆]-octahedra.By solution calorimetry and e.m.f. measurements in galvanic cells for solid electrolytes could be proved that all compounds are formed from NaCl and LnCl₃ by gain in lattice enthalpy.This revised version was published online in November 2005 with corrections to the Cover Date.