Inclusion compounds of N,N,N′,N′-tetraisopropylfumaride with isomers of methyl phenol and water

The crystal structures and thermal analyses of the host compound, N,N,N,N-tetraisopropylfumaride, witho-cresol,m-cresol and water are reported and compared to that of thep-cresol complex previously reported in an attempt to elucidate the reasons for host selectivity.     

STRUCTURAL ANALYSIS AND ENVIRONMENTAL STABILITY OF POLYFLUORINATED GROUP SUBSTITUTED POLYTHIOPHENES

Electrochemical polymerization of 3-fluoroalkoxy and 3-fluoroether thiophenes givespolymers with relatively high molecular weights and good processibility. Investigationof these polymers by means of GPC indicates that an increase in the number of fluorineatoms in the fluorinated group results in a decrease in degree of polymerization of thepolymers in the same polythiophene series. As shown by NMR and FTIR, the polyfluo-rinated group substituted polythiophenes have regular 2, 5-coupling in their main chains.The SEM micrographs of the polymer films exhibit that polymer (1)-poly [3-2, 2, 3, 3-tetrafluoro-propoxy) thiophene] possesses more regular structure than the other polymersdo. Substitution of polythiophenes by fluorinated groups leads to the polymers with highelectric, electrochemical and thermal stability.     

莲子草假隔链格孢毒素的分离纯化与结构鉴定

从莲子草假隔链格孢(Nimbya alternantherae)中分离纯化了一种毒素物质, 并对其进行了结构鉴定, 为研究其致病机理及进一步的化学合成奠定了基础.     

Influence of the PVdF binder on the stability of LiCoO2 electrodes

We report herein on the effect of the PVdF binder on the stability of composite LiCoO₂ electrodes at elevated temperatures in 1 M LiPF₆ EC/EMC solutions at open circuit conditions. The structure and morphology of composite LiCoO₂ electrodes with different combinations of electrode components (LiCoO₂ active material, PVdF binder, carbon black and current collector) were evaluated by Raman spectroscopy, X-ray diffraction and SEM. The content of Co ions in the electrolyte solutions was determined by ICP. A new effect was discovered, namely, a detrimental impact of the contact between PVdF and LiCoO₂ on the stability of the active mass. The formation of surface Co₃O₄ and dissolution of Co ions at elevated temperatures is accelerated at the contact points between the active mass and the binder. The effect of water content in the electrolyte solutions on the stability of LiCoO₂ was also studied. The presence of water (and/or HF) is a necessary condition for the accelerated dissolution of Co ions from the active mass. LiCoO₂ oxidizes the solvents at elevated temperatures thus forming CO₂.     

Orientation disorder in ammonium elpasolites: Crystal structures of (NH4)3AlF6, (NH4)3TiOF5 and (NH4)3FeF6

Crystal structures of the known (NH₄)₃AlF₆(I) and (NH₄)₃FeF₆(III) and new (NH₄)₃TiOF₅(II) elpasolites were refined by localizing anions (F⁻, O²⁻) in four acceptable positions of the cubic system Fm3m (Z=4) with a=8.9401(3), 9.1104(3), 9.110(1) Å, respectively. According to the refinement data and a rather large entropy change due to fluorine (oxygen) octahedra disordering in the above compounds and in (NH₄)₃WO₃F₃(IV) elpasolite, it was found that fluorine (oxygen) atoms are randomly distributed in two ways, in general 192l position or in mixed 24e + 96j one. Statistics in fluorine (oxygen) distribution is, probably, the result of domain structure of the crystals.     

Chirality,twist and structures of micellar lyotropic cholesteric liquid crystals in comparison to the properties of chiralic thermotropic phases

Phase chirality in disk-like lyotropic cholesteric phases (Ch(D)) was investigated, which was induced by addition of center and axial chiral dopants to achiral lyotropic nematic host phases (N(D)). In a lyotropic nematic matrix of the disk-like N(D) phase in the ternary system hexadecyldimethylethyl ammonium bromide (C16Me2EABr)/water/n-decanol, a disk-like lyotropic cholesteric phase Ch(D) was induced by addition of the axial optically active compound R(-)-1,1'-binaphthalene-2,2'-diyl-hydrogen-phosphate (BDP). The helical twisting power (HTP) of the BDP is generally lower than the HTP value of inducing substances with center chirality as cholesterol, prednisolone and taurocholic acid. At constant composition of the N(D) phase, the helix lengths were determined in dependence on the BDP and steroid concentration by means of evaluation of the 'spaghetti-like' texture using polarizing microscopy. The reciprocal helix lengths are changing linearly with rising BDP concentration. The properties of the Ch(D) phase (textures, helix lengths, structural parameters of the micelles) induced by the chiral compounds and changed by the composition of host phases can give information to the mechanism of chirality transfer from the molecular level to that of the micellar aggregates and finally, to the liquid crystalline superstructure. Furthermore, the matrix influence of the N(D) phase on the helix formation was examined at constant BDP and steroid concentration. The structure in the Ch(D) phase was described in terms of micelle parameters. Finally, the inducing properties of a center chiral optically active compound such as cholesterol, prednisolone and taurocholic acid were compared with those of the axial chiral compound BDP. Last but not least, the situation of the theoretical and structural background for helix formation in liquid crystals, e.g. the explanation of chiralic transfer between micelles is analyzed and discussed. Two main conditions are necessary to build up the helix in the Ch(D) phase: the formation of H-bridges; and the existence of a specific chiralic interaction energy between neighboring micelles in the cholesteric superstructure.     

Two new saponins from Anemarrhena asphodeloides Bge.

Two new saponins 3-O-β-D-glucopyranosyl (1→2)-β-D-mannopyranosyl sarsasapogenin, named timosaponin A IV(1) and (5β, 25S)-26-O-β-D-glucopyranosyl-furost-20(22)-en-3,26-diol-3-O-β-D-glucopyranosyl (1→4) glucopyranosyl (1→2)-β-D-galacopyranoside, named timosaponin B IV(2), were isolated by silica gel column chromatography and preparative HPLC from Anemarrhena asphodeloides Bge. Their structures were elucidated by chemical characters and spectroscopic analysis.     

交替烃拓扑结构计数的研究

交替烃拓扑结构计数的研究余荣泮，杨良准，刘训亭，胡启山，张自先，莫宇翔，陈琼，王成瑞（武汉大学化学系武汉４３００７２）关键词拓扑结构计数，交替烃，分子轨道分子稳定性的研究是理论化学中一个重要课题，关于这方面的工作，共振论是富有成效的理论之一。在偶苯型...     

具有优良结构稳定性的Ni73P11B16非晶态合金超细微粒

具有优良结构稳定性的Ｎｉ_（７３）Ｐ_（１１）Ｂ_（１６）非晶态合金超细微粒范以宁，胡征，许昭怡，陈懿（南京大学化学系，南京，２１０００８）关键词非晶态，ＮｉＰＢ合金，超细微粒，结构稳定性非晶态合金催化剂以其优良的催化性能而引起人们的广泛关注［１］。在?..     

Influence of silica fillers during the electron irradiations of DGEBA/TETA epoxy resins, part I: Study of the chemical modification on model compounds

The study of the chemical modifications of model compounds of the diglycidyl ether of bisphenol A/triethylene tetramine (DGEBA/TETA) epoxy resins under electron irradiation is described. The reaction of butylamine and N,N′-diethylethylene diamine with DGEBA afforded model compounds of the DGEBA/TETA structure. Nanometric silica was used as filler for these model compounds. ¹H and ¹³C NMR analyses allowed identification of the chemical structures before and after irradiation. C-O and C-N scissions were observed with the formation of phenolic and methyl-ketone ends and of primary and secondary amines. For the model compounds containing the 1,2-diaminoethylene structure, the scission of the C-N bond is followed by the formation of an enamine end. The mechanisms of the different bond scissions are proposed. The presence of the nanometric silica fillers allows the protection of some C-N bonds. The reaction of the chemical species formed by electron irradiation with the reactive functions at the silica surface is proposed to explain the chemical modifications observed on the irradiated filled model compounds.