Structural Characterizations of Spherical Octadecavanadates Encapsulating Na+, K+ or I- and Ellipsoidal Octadecamolybdate Encapsulating two Anions of SO42-

Polyoxoanions of tungsten, molybdenum, and vanadium have been the subject of interest since their wide variety of compositions, structures, and properties give rise to numerous important applications^[1]. From the NH₄VO₃/Na₂S_x (or (NH₄)₂S_x) reaction system we synthesized several spherical octadecavanadates with Na⁺,K⁺, NH₄⁺ or I encapsulated using hydrothermal method. These complexes include (NH₄)₁₁[V₁₈O₄₂(Na)]·(H₂O)₂₀ 1; (NH₄)₁₁[V₁₈O₄₂(K)]·(H₂O)₆, 2; (NH₄)₁₀(Na)[V₁₈O₄₂(Na)]·(H₂O)₂₆, 3; (NH₄)₁₁[V₁₈O₄₂(NH4]·(H₂O)₂₀, 4; and (NH₄)₂₀(I)₇[V₁₈O₄₂(I)]·(H₂O)₁₂, 5, in which the structures of 1, 2, 3, and 5 have been determined by X-ray analyses. In the analogous reaction system of (NH₄)₂MoS₄/(NH₄)₂S_x, we also obtained one ellipsoidal octadecamolybdate, (NH₄)₄[Mo₁₈O₅₄(2SO₄)]·(H₂O)₄, 6 with a standard Wells-Dawson structure^[2]. The Ortep drawings of the two kinds of structures are viewed as follows.     

8-羟基喹啉合十钒酸盐的研究(Ⅲ)——锂、钾、铵盐的合成、鉴定与性质

在合成与研究钠盐的基础上^[1,2],我们又合成了锂、钾和铵盐,通过元素分析、分子量测定、质谱分析、X射线衍射、紫外和红外吸收光谱分析和热重分析确定了新化合物的组成与化学式并推测了化合物的结构式。     

NMR Study on the Hydration of Ions in Microemulsion——Bis-2-Ethylhexyl Phosphoric Acid-Alcohol-Kerosine-Water System

In the present investigation we have observed the proton shift of water of hydration of metal ions in a microemulsion formed by adding water gradually front 0.05% to 20% to a moisture-free bis-2-ethflhexyl phosphoric acid-alcohol-kerosine sistem saponified by metallic sodium,so that the mole ratio of concentration (M )/V(H2O) can be varied from 100:1 to 1:100.Under such conditions,we have obtained the lirni's of SME for various cations as follows 6.78PPm(NH4 ),6.80(Li ).5.96(Na ).6.40(K ),in comparison with the proton shift of liquid water,H2O=4.80PPm.     

Measurement of Solid-liquid Equilibria in Quaternary System Li+, K+//SO42-, B4O72--H2O at 288 K

In order to utilize the brine resources in China, the solid-liquid equilibria in quaternary system Li⁺, K⁺//SO₄^2-, B₄O₇^2--H₂O at 288 K was studied by the isothermal solution equilibrium method. Solubilities and densities of solutions were determined experimentally. According to the experimental data, the equilibrium phase diagrams, density-composition diagram and corresponding water content diagram of the quaternary system were plotted. Double salt KLiSO₄ was found in the reciprocal quaternary system Li⁺, K⁺//SO₄^2-, B₄O₇^2--H₂O at 288 K. The quaternary system has three invariant points, seven univariant curves and five fields of crystallization. The five crystallization regions correspond to Li₂B₄O₇·3H₂O, Li₂SO₄·H₂O, K₂B₄O₇·4H₂O, K₂SO₄ and KLiSO₄, respectively. The crystallization field of salt Li₂B₄O₇·3H₂O is the largest, whereas that of Li₂SO₄·H₂O is the smallest. The experimental results show that Li₂SO₄·H₂O has a strong salting-out effect on other salts.     

Highly Uniform Alkali Doped Cobalt Oxide Derived from Anionic Metal-Organic Framework: Improving Activity and Water Tolerance for CO Oxidation

A sequence of alkali metal cation-exchanged Co metal-organic frameworks(Co-MOFs), therein after denoted as M@Co-MOF, M=Na⁺, K⁺, Rb⁺, and Cs⁺, was prepared and used as the precursors to obtain the corresponding alkali doped cobalt oxide(defined as M/Co₃O₄, M=Na⁺, K⁺, Rb⁺, and Cs⁺) through calcination under air atmosphere. The cobalt oxide modified by uniform alkali metals exhibited a significant promotion of catalytic activity for CO oxidation. The activity of M/Co₃O₄ decreased in the order of Cs⁺ > Na⁺ > K⁺ > Rb⁺. Experimental and theoretical results revealed that the anionic skeleton of Co-MOF could facilely adsorb alkali metal cations and play a crucial role in the formation of highly uniform alkali doped cobalt oxide. The further characterizations, such as temperature-programmed reduction of H₂(H₂-TPR), oxygen temperature-programmed desorption(O₂-TPD), X-ray photoelectron spectroscopy(XPS), and in situ diffuse reflectance infrared Fourier transform(DRIFT) spectra demonstrated that the enhanced catalytic activity is originated from the interfacial electron transfer as well as weakened the Co-O bond strength, which promoted oxygen desorption from Co₃O₄ and formation of cobalt species with the lower valence state. The Cs/Co₃O₄ catalyst was maintained for 60 h without deactivation and still showed a high activity in the presence of water.     

Isothermal Evaporation of Quaternary System Li^＋, K^＋, Mg^2＋//Cl^--H2O at 348K

The solubilities of the quaternary system Li^＋,K^＋,Mg2^＋//Cl^--H2O were investigated at 348 K via isothermal evaporation.The densities and refractive indices of its equilibrated solution were also determined experimentally.On the basis of the obtained data,the metastable phase diagram,the water content diagram,the diagrams of the density and refractive index against the composition of this quaternary system were constructed.The quaternary system Li^＋,K^＋,Mg^2＋//Cl^--H2O at 348 K belongs to a complex type with the formation of two carnallite double salts,which are potassium carnallite（K-carnallite） and lithium carnallite（Li-carnallite）.There are five salts like potassium chloride （KCl）,lithium chloride monohydrate（LiCl.H2O）,bischofite（MgCl2·6H2O）,K-carnallite（KCl·MgCl2·6H2O） and Li-carnallite（LiCl·MgCl2·7H2O）,seven unvariant curves named AH3,BH2,CH3,DH1,EH1,H1H2 and H2H3,and three invariant points,namely H1,H2 and H3,included in this metastable phase diagram.Comparisons between the stable phase diagram at 298 K and metastable phase diagram at 348 K of this quaternary system show that all the crystalline forms of the salts are not changed,whereas the crystallization areas of salts are changed significantly with temperature.The scope of KCl crystallization increases from 82% to 95% and that of K-carnallite decreases from 15.80% to 0.32% along with the temperature increasing from 298 K to 348 K,respectively.     

离子水化过程的核磁共振研究——二-(2-乙基己基)膦酸-长链醇-煤油-水体系

本文利用无水皂化萃取剂加水生成微乳状液研究离子水化的新方法,研究了酸性膦酸酯D₂EHPA(碱金属盐)-ROH-煤油-水体系中,通过对水质子化学位移变化的规律来研究碱金属的水合作用,所得结果与环烷酸体系相似。当[M⁺]/[H₂O]从100/1向1/100变化时,可以看到配位水的化学位移比缔合水(即正常液体水)向低场移动近2ppm,这比通常在浓盐水溶液中观察到的差值提高了一个数量级。当[M⁺]/[H₂O]大于100/1时,配位水的化学位移随阳离子不同而趋于不同的极限值,其顺序为NH₄⁺(6.76)>Li⁺(6.60)>Na⁺(5.96)>K⁺(5.40)。 从不同体系NMR图峰形和半高宽度Δv_1/2的变化,可以观察到阴离子的结构和组成对离子的水化作用有较大的影响。有关阴离子水合情况的研究工作正在进行中。     

Structure and stability of endohedral X@Si20H20 complexes (X = Li, Na, K, Be, Mg, Ca)

The structure and stability of endohedral X@Si₂₀H₂₀ complexes (X = Li^0/+, Na^0/+, K^0/+, Be^0/2+, Mg^0/2+, Ca^0/2+) have been studied at the B3LYP/6-31G* level of density functional theory. It is found that complexes with X = Na^0/+, K^0/+, Mg and Ca^0/2+ are energy minimum structures with X at the cage center in I_h symmetry, while those with X = Li^0/+, Be^0/2+, Mg²⁺ have off-centered structures with X towards one pentagon face in C_5v symmetry. Large electron or charge transfer between the Si₂₀H₂₀ cage and the encapsulated X has been observed.     

Construction of a nano-rectangular Zn-Nd complex with near-infrared luminescent response towards metal ions

One 6-metal Zn-Nd complex[Zn₂Nd₄L₂(OAc)₁₀(OH)₂(CH₃OH)₂](1)with Schiff base ligand bis(3-methoxysalicylidene)ethylene-1,2-phenylenediamine(H₂L)was constructed,and it has nanoscale rectangular structure(8×11×28 A).Excited by ligand-centered absorption bands,1 shows NIRemission of Nd³⁺ion.Interestingly,1 exhibits lanthanide luminescent response towards metal ions,especially to alkali metal ions(Li⁺,Na⁺ and K⁺)at ppm level.     

丙烷脱氢负载型PtSnNa/SUZ-4催化剂中Na+助剂组分的作用

用微型催化反应装置结合X射线衍射(XRD)、H₂化学吸附、NH₃吸附-程序升温脱附(NH₃-TPD)和H₂-程序升温还原等多种物理化学手段研究了丙烷脱氢负载型PtSnNa/SUZ-4催化剂中Na⁺助剂组分的作用。结果表明,Na⁺组分可中和SUZ-4载体表面的强酸中心、提高催化剂的Pt金属分散度、抑制脱氢产物的裂解和积炭的生成,从而提高催化剂的丙烷脱氢选择性和反应稳定性。但是过量Na⁺组分的存在会削弱Sn物种与载体之间的相互作用,使其易被还原,导致催化剂丙烷脱氢活性显著下降。     

Gas-phase chemistry of nitrogen trifluoride NF3: structure and stability of its M–NF3 (M=H, Li, Na, K) complexes

The stationary points characterizing the potential energy profiles of the complex processes of the M⁺(M=H, Li, Na, K) and NF₃ were investigated by QCISD and B3LYP in conjunction with the 6-311+G(2d,2p) basis set. The optimized geometries and NBO analysis indicate that the complexes of M⁺(M=Li, Na, K) and NF₃ exist as ion-dipole molecules. But for H⁺ complexes, there are two stable isomers NF₃H⁺ and NF₂⁺–HF. The interaction distances of isomers follow the sequence H⁺< Li⁺< Na⁺< K⁺. The calculated affinity energies of the most stable isomers of H⁺, Li⁺, Na⁺, and K⁺ complexes exceed 20.1 kJ/mol, and these values suggest that the M⁺–NF₃ (M=H, Li, Na, K) complexes could be observed as stable species in gas phase, which supports Fujii's proposal that Li⁺ ion attachment mass spectrometry can serve as a conceivable technique to quantify the emissions of the NF₃.     

ESI MS, spectroscopic and PM5 semiempirical studies of Colchicine complexes with lithium, sodium and potassium salts

The colchicine complexes with Li⁺, Na⁺ and K⁺ cations have been synthesized and studied by ESI MS, ¹H and ¹³C NMR, FT-IR and PM5 semiempirical methods. It has been shown that colchicine forms stable complexes of 1:1 stoichiometry with monovalent metal cations. For Li⁺ cations also formation of the 2:1 stoichiometry complexes has been detected. The most stable structures of the complexes are those in which the acetamide groups are involved in the coordination process. The structures of the colchicine complexes with Li⁺, Na⁺ and K⁺ cations are visualized and discussed in details.     

The use of MIDI basis set at the correlated level

The H₂O + H₂O, the NH₃ + NH₃, the BH₃ + H₂O and the Ne + Ne systems have been studied in the supermolecule approach, using several medium sized basis sets (especially the so-called MIDI basis set). The calculations have been carried out by the use of localized molecular orbitals (LMOs).

The dispersion interaction energies have been computed by a new method (Kozmutza and Kapuy; Int. J. Quantum Chem., 38 (1990) 665), whose essence lies in the use of LMO contributions at the correlated level.

The method proposed seems to be useful for the H₂O + H₂O, the NH₃ + NH₃, and the Ne + Ne systems at different intermolecular distances, using the MIDI basis, but fails in describing correctly the correlation energy for the BH₃ + H₂O system.     

Raman spectroscopic study of the conformational change of 12-crown-4 due to cation capture

Raman spectra of the Li⁺, Na⁺, K⁺, NH⁺₄, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Pb²⁺ complexes of 12-crown-4 and also 12-crown-4 in various states are observed. The spectra of 12-crown-4 change remarkably by complex formation with cations. Normal vibration calculations of various conformations of 12-crown-4 are carried out. On the basis of the observed spectra and the results of the calculations, the conformation of 12-crown-4 in the Li⁺, Na⁺, K⁺, NH⁺₄, Mg²⁺ complexes is found to have approximate D_2d symmetry, while that in the Ca²⁺, Sr²⁺, Ba²⁺ complexes is found to have approximate C_2V symmetry.     

Solid-liquid Equilibria in the Quaternary System Na＋, K＋//Br-, B4O72--H2O at 298 K

According to the compositions of the underground gasfield brines in the west of Sichuan Basin, the solu- bilities and densities of the solid-liquid equilibria in the quaternary system Na＋, K＋//Br-, B4O72--H2O at 298 K were determined by the method of isothermal solution saturation. From the experimental data, the phase diagram, water content diagram and density-composition diagram were obtained. This quaternary system is of simple eutectic type, without double salt and solid solution. There are two invariant points, five univariant curves, four fields of crystalli- zation in the system. The equilibrium solid phases are Na2BaO7·10H20, K2B4O7·4H2O, NaBr·2H2O and KBr. Na2B4O7·10H2O has a larger crystallization field, and NaBr·2H2O has a smaller crystallization field. It is also found that bromide has the salting-out effect on borate in the quaternary system Na＋, K＋//Br-, B4O72--H2Oat 298 K.     

溶液中杯[4]芳烃双冠-6与Cs~+配位化学研究

研究了溶液中杯[4]芳烃双冠-6(BisC₆)与Cs⁺配位行为.常温下,BisC₆/NPME(邻硝基苯甲醚)体系单级萃铯百分率达99.36%,模拟料液中,Cs⁺/Na⁺和Cs⁺/K²⁺分离系数分别为3.92×10⁴和2.21×10⁴.局域结构模型实验表明,配合物分子中可能存在水或(和)硝酸(根).ESI-MS谱表明,NPME体系中,铯离子与BisC₆同时形成1:1(单核)和2:1(双核)的配合物,并且存在[BisC₆·H₂O],[BisC₆·Cs⁺]⁺,[BisC₆·2Cs⁺·H₂O]₂+和[BisC₆·2Cs₁₀⁺·No₁₀^-3]10⁺等多种配合物分子.EXAFS实验表明,溶液中铯离子的配位数为7,形成7个氧配位的稳定结构,ADF计算验证了EXAFS实验结果.     

新型类沸石金属-有机骨架材料用于天然气中CO2的分离

研究了在usf型类沸石金属-有机骨架材料(usf-ZMOF)中不同金属离子(Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺, Al³⁺)对天然气分离(以CO₂/CH₄, CO₂/H₂, CO₂/N₂为研究对象)的不同影响. 结果表明, 此类材料对于3种体系的分离选择性均高于现有材料. 其中性能最好的是Al-usf-ZMOF, 其对CO₂/CH₄, CO₂/N₂和CO₂/H₂的分离选择性分别为290, 1700和16800. 同时, 对于经不同的离子交换后的usf-ZMOF, 吸附选择性随着离子电荷值的增加而增大; 对于同一主族的离子, 选择性随着原子序数的增加而减小. 而上述现象的产生是由阳离子和CO₂间的强静电作用所致.     

Spectroscopic, mass spectrometry, and semiempirical investigations of a new 2-(2-methoxyethoxy)ethyl ester of Monensin A and its complexes with monovalent cations

A new 2-(2-methoxyethoxy)ethyl ester of Monensin A (MON7) has been synthesized and its capability of complex formation with Li⁺, Na⁺, and K⁺ cations has been studied by ESI MS, ¹H and ¹³C NMR, FT-IR, and PM5 semiempirical methods. ESI mass spectrometry indicates that MON7 forms complexes with Li⁺, Na⁺, and K⁺ of exclusively 1:1 stoichiometry which are stable up to cv = 70 V. The formation of complexes between MON7 and Na⁺ cations is strongly favored. Starting from about cv = 90 V fragmentation of the respective complexes is observed, primarily characterized by several dehydration steps. The structures of the MON7 complexes with Li⁺, Na⁺, and K⁺ cations are stabilized by intramolecular hydrogen bonds in which the OH groups are always involved. The structures are visualized and discussed in detail. It has been proved that the formation of a pseudo crown ring structure formed by MON7 is preferred in complexes with Na⁺ cations.     

Influence of cations on the proton leakage through anion-exchange membranes

In the recovery of acids from wastewaters or the regeneration of acids and bases from salts by electromembrane processes, the most important phenomenon which limits the current efficiency is the transport of protons through the anion-exchange membrane (AEM). In this work, the proton leakage through an AEM is studied with a system containing hydrochloric acid or sulfuric acid on the cathodic side and the mixture of acid with one homoanionic salt (Li⁺, Na⁺, K⁺, Cr³⁺, NH₄⁺, (CH₃)₄N⁺ and (C₂H₅)₄N⁺) on the anodic side. The proton leakage is quantified from the value of the proton transport number. The results are analyzed assuming that the rate determining step of proton leakage is the interfacial transfer reaction of protons from the aqueous anodic solution to the membrane. The proton leakage is enhanced by the polarizing power of the cation. The transfer of protons into the membrane seems to be catalyzed by the presence of a layer of adsorbed cations on the surface of the membrane. The presence of salt decreases the proton leakage but it is always greater with H₂SO₄ solutions compared to HCl solutions.     

Synthesis and H-NMR complexation studies of alkalimetal bithioxanthylidene crown ether complexes

Two synthetic routes to a novel class of sterically overcrowded alkenes, bithioxanthylidene crown ethers 1, are described. The ¹H spin-lattice relaxation times (T₁) of the crown ethers as well as those of the corresponding complexes with Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺ in CDCl₃ were measured and the results were interpreted in terms of complexation affinities.