DFT study and Monte Carlo simulation on proton transfers of 2-amino-2-oxazoline, 2-amino-2-thiazoline, and 2-amino-2-imidazoline in the gas phase and in water

Density functional theory (DFT) and Monte Carlo (MC) simulation with free energy perturbation (FEP) techniques have been used to study the tautomeric proton transfer reaction of 2-amino-2-oxazoline, 2-amino-2-thiazoline, and 2-amino-2-imidazoline in the gas phase and in water. Two reaction pathways were considered: the direct and water-assisted transfers. The optimized structures and thermodynamic properties of stationary points for the title reaction system in the gas phase were calculated at the B3LYP/6-311+G(d, p) level of theory. The potential energy profiles along the minimum energy path in the gas phase and in water were obtained. The study of the solvent effect of water on the proton transfer of 2-amino-2-oxozoline, 2-amino-2-thiazoline, and 2-amino-2-imidazoline indicates that water as a solvent is favorable for the water-assisted process and slows down the rate of the direct transfer pathway.     

电极条件对硫酸介质中电解还原提纯镱过程的影响

研究了以钌铱钛合金网和汞分别为阳、阴电极, 在无气氛保护条件下, 采用电解还原方法从铥、镱、镥硫酸盐溶液中分离提纯镱的过程. 讨论了在8 V恒电压时的电极间距、位置, 以及阴、阳极表面积对电解过程中的电流、还原率影响. 优化了电解还原过程, YbSO4产品的纯度稳定达到99.5%以上, 一次收率可达80%;提镱后母液中的铥和镥被富集4倍以上, 其中Lu含量高于50%, 十分有利于后续铥/镥分离.     

Permeation of particle through a four-helix-bundle model channel

By using molecular dynamics simulation, the dynamic behaviors of particle permeation through a four-helix-bundle model channel are studied. The interior cavity of the four-helix-bundle provides the "routes" for particle permeation. The main structural properties of the model channel are similar to those that appear in natural four-helix-bundle proteins. It is found that the interior structure of the model channel may greatly influence the permeation process. At the narrow necks of the model channel, the particle would be trapped during the permeation. There is a threshold value for the driving force. When the driving force is larger than this threshold value, the mean first permeation time decreases sharply and tends to be saturated. Increasing the temperature of either the model channel or the particle reservoir can also facilitate the permeation. Enhancing the interaction strength between the particle and monomer on the four-helix-bundle model chain will hinder the permeation. Hence, the electrical current which is induced by the particle permeation is a function of the driving force and temperature. It is found that this current increases monotonically as the strength of the driving force or the temperature increases, but decreases as the interaction strength between the particle and monomer increases. It is also found that the larger the friction coefficient, the slower the permeation is. In addition, the multiparticle (or multi-ion) permeation process is also studied. The permeation of multiparticle is usually quicker than that of the single particle. The permeation of particle through a five-helix-bundle shows similar properties as that through a four-helix-bundle.     

Preparation and Characterization of Sol-Gel SE-30-Coated Silica Stationary Phase for Capillary Liquid Chromatography

A sol-gel chemistry-based polymer coating approach was developed for the preparation of a novel polysiloxane-coated silica stationary phase for capillary liquid chromatography. SE-30, a commercial polysiloxane stationary phase used in gas chromatography, was incorporated into the properly designed sol solution. Then the sol-gel mixture was introduced into a silica gel-packed capillary column by pressure. A thin film of sol-gel SE-30-coating is chemically bonded to the surface of silica gel particles by hydrolytic polycondensation under mild conditions without any free radical cross-linking procedures, therefore the sol-gel approach offers a simple and effective pathway to create a hybrid polymer-coated silica stationary phase. Various factors affecting column making were optimized and discussed in this report. The resulting stationary phase showed good permeability, mechanical robustness, high durability to alkaline mobile phase and satisfactory chromatographic performance in separations of polar and non-polar aromatic compounds. Linear solvation energy relationships (LSERs) studies indicate that the stationary phase has a reversed-phased character with SE-30 providing chromatographic functionality. The solute size and the solute hydrogen bond ability are major factors that principally govern the retention of test solutes.     

链状[NH3CH2CH2NH3]AgAsS4的溶剂热合成及表征

利用溶剂热方法合成了链状[NH3CH2CH2NH3]AgAsS4,通过单晶X射线衍射技术对其进行了晶体结构分析,该化合物晶体属单斜晶系,空间群C2/c,晶胞参数a=1.35805(8)nm,b=0.65331(3)nm,c=2.27711(9)nm,β=106.42(3)°,Z=8.化合物具有有趣的梯子状双链结构,该阴离子链由AsS4与AgS3共用顶点交替连接而成,有机阳离子在阴离子链之间存在较强的N—H…S氢键.DSC和Tg分析结果表明化合物在200℃以下是稳定的.     

有机-无机杂化凝胶法合成YAG∶Ce~(3+)荧光粉的包膜及其稳定性

本文以金属硝酸盐为原料,柠檬酸为配位剂的有机-无机杂化凝胶法来合成掺杂三价铈离子的钇铝石榴石荧光粉,采用X-射线衍射法研究了杂化凝胶在煅烧过程中的相转变机制。结果表明:杂化凝胶在煅烧过程中可以通过两条途径形成Y3Al5O12(YAG)相:一是由无定形Y2O3和Al2O3直接向YAG相的一步相转变;二是由无定型Y2O3和Al2O3经由YAlO3(YAP)和γ-Al2O3向YAG相的两阶段相转变,在900℃得到结晶性好的纯YAG∶Ce3 荧光粉,其最大激发波长为459nm,最大发射峰波长为550nm;在荧光粉表面包覆氧化铝和氧化镧,将使荧光粉的荧光强度稍有降低,但对荧光粉的稳定性有很好的改进作用。     

Synthesis of trans‐disubstituted cyclam ligands appended with two 6‐hydroxymethylpyridin‐2‐ylmethyl sidearms: Crystal structures of the 1,8‐dimethyl‐4,ll‐di(6‐hydroxymethylpyridin‐2‐ylmethyl)cylam ligand and its Co(II) and Ni(II) complexes

Two new trans‐disubstituted cyclam ligands; 1,8‐di(6‐hydroxymethylpyridin‐2‐ylmethyl)‐1,4,8,11‐tetra‐azacyclotetradecane ( 5 ) and 1,8‐dimethyl‐4, 11‐di(6‐hydroxymethylpyridin‐2‐ylmethyl)‐1,4,8,11 ‐tetraaza‐cyclotetradecane ( 6 ); have been synthesized and characterized. The crystal structures of ligand 6 and its Ni(II) and Co(II) complexes have been determined. Crystal data are given for 6 , space group, P2₁/c, a = 11.095 (6) Å, b = 9.467 (5) Å, c = 13.283 (8) Å; β = 106.95 (5)°, Z = 2, R = 0.0715; for [Ni 6 ](C10₄)₂, space group P2₁/c, a = 9.4848 (14) Å, b = 33.941(6) Å, c = 9.793(2) A, β = 95.264(14)°, Z = 4, R = 0.0567; for [Co 6 ](C10₄)₂, space group, P2₁/c, a = 9.440 (6) Å, b = 33.848 (13) Å, c = 9.820 (3) Å, β = 95.16(3)°, Z = 4, R = 0.0718. In both complexes, the metal atoms are six‐coordinate with only one of the pendants interacting with the central metal atom and the other pendant remaining uncoordinated.     

TPSR STUDIES OF THE ACTIVATION OF METHANE ON SUPPORTED PLATINUM CATALYSTS

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STUDIES OF THE HOMOLOGATION OF METHANE ONSUPPORTED TRANSITION METAL CATALYSTS

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8-羟基喹啉单体及二聚体质子转移反应的理论研究

Density functional theory （DFT） of quantum chemistry method was employed to investigate proton transfer reactions of 8-hydroxyquinoline （8-HQ） monomers and dimers. By studying the potential energy curves of the isomerization, the most possible reaction pathway was found. The total energy of 8-hydroxyquinoline was lower than that of quinolin-8（1H）-one, whereas the order was reversed in dimers. The findings explained the contrary experimental phenomena. The minimum reaction barrier of intramolecular proton transfer was 47.3 kJ/mol while that in dimer was only 25.7 kJ/mol. Hence it is obvious that proton transfer reactions of 8-HQ monomer have a considerable rate but it is easier to proceed for 8-HQ dimer than monomers. It implied that the hydrogen bond played an important role in depressing the activation energy of reaction. The mechanism of the tautomerization was discussed on the basis of theoretical results.