Liquid Crystals Based on the N-Phenylpyridinium Cation—Mesomorphism and the Effect of the Anion

Families of symmetric, ionic, tetracatenar mesogens are described based on a rigid, N-phenylpyridinium core, prepared as their triflimide, octyl sulfate and dodecyl sulfate salts for a range of terminal chain lengths. The mesomorphism of the individual series is described before a comparison is drawn between the different families and then more broadly with (i) neutral tetracatenar materials and (ii) related bis(3,4-dialkoxystilbazole)silver(I) salts. For the octyl and dodecyl sulfates and the related triflates reported earlier, a SmA phase is seen at shorter chain lengths, giving way to a Col_h phase as the terminal chain lengthens. For the alkyl sulfate salts, an intermediate cubic phase is also seen and the terminal chain length required to cause the change from lamellar to columnar mesophase depends on the anion. Furthermore, there is an unexpected and sometime very large mesophase stabilisation seen on entering the columnar phase. All of the triflimide salts show a rectangular columnar (ribbon) phase.     

Discotic Liquid Crystals of Transition Metal Complexes, 19: Discotic Mesomorphism and Double Clearing Behavior of Octakis(dialkoxyphenyl)phthalocyanine Derivatives

Eight novel octakis(3,4-dialkoxyphenyl)- phthalocyanine derivatives, Cn-M (2, M=2H; 3, M=Ni; 4, M=Cu; a, decyloxy; b, undecyloxy; c, dodecyloxy), have been synthesized and characterized. It was found that each of the derivatives exhibits discotic liquid crystalline properties, and that each of the Cn–Cu (4) derivatives has two kinds of D_rd2( P 2₁/ a ) mesophases. These Cn–Cu (4a,b,c) and C₁₂–2H (2c) derivatives exhibit a unique double clearing behavior.     

s‐Triazine‐Based Functional Discotic Liquid Crystals: Synthesis,Mesomorphism and Photoluminescence

A new series of C₃‐symmetric, π‐conjugated molecules was designed, synthesized and characterized. The materials were derived from electron‐accepting s‐triazine, appended covalently to electron‐donating styrylbenzene arms, and were readily prepared in excellent yield with high purity by means of three‐fold condensation of triphosphonate with n‐alkoxybenzaldehydes under Horner–Wadsworth–Emmons reaction conditions. Examination of the phase transitional properties by several complementary techniques evidenced self‐assembly into a hexagonal columnar phase, occurring over wide and reasonable thermal ranges. The photophysical properties were studied both in solution and in the fluid/frozen columnar states by UV/Vis absorption and photoluminescence spectroscopy. The emission spectra obtained as a function of the temperature rule out the breaking‐up of larger columns and a non‐radiative, thermally activated process. A study carried out on thin films of the glassy columnar state, which accounts for conserved fluorescence, defect‐free orientation, and freezing ionic species, with the help of atomic force microscopy (AFM) images, suggested a homogeneous granular morphology comprising fibrillar structures. Dissimilarities in the surface morphology and birefringence of thin films of the solid and frozen columnar states were clearly shown by Raman spectroscopy. An electrochemical investigation revealed a LUMO energy of ?4.0 eV. Thus, the discotic motifs presented herein meet certain criteria of organic materials, which are essential for developing electronic devices.     

苯并菲盘状液晶的合成、亲氟效应及分子对称性对介晶性的影响

New symmetrical and asymmetrical triphenylene-containing discotic liquid crystals with two different peripheral alkyl chains, known as sym-TP(OC6H13)3(OR)3 and asym-TP(OC6H13)3(OR)3, were synthesized. Their thermotropic liquid crystal properties were investigated through polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses. The asyrranetdcal discogens are 2,6,11-rialkoxy-3,7,10-trihexyloxytriphenylenes, with the alkyl chain carbon numbers varying from 3-10, 12, and 14, while the symmetrical compounds are 2,6,10-trialkyloxy-3,7,11-trihexyloxytriphenylene. Two fluoroalkoxy substituted triphenylene discogens, 2,6,10-td(4,4,4-trifluorobutoxy)-3,7,11-trihexyloxytriphenylene and its asymmetrical isomer 2,6,11-tri(4,4,4-trifluorobutoxy)-3,7,10-trihexyloxytdphenylene were prepared. These two compounds show higher melting and clearing points than their alkoxy analogs, which implies that fluorophilic effect exists in the formation and stabilization of discotic columnar mesophase. The triphenylene derivatives TP(OC6H13)3(OR)3 with two different peripheral chains, symmetrically or asymmetrically attached on triphenylene cores, have lower melting points and clearing points than those of the higher symmetrical compounds TP(OR)6 with the same total chain carbon numbers. The mixed-chain-triphenylenes with longer alkoxy chains (n=9,10,12,14) show columnarmesophase at room temperature.     

Influence of Confinement on The Phase Transition And Spectral Characteristics of Nematic Liquid Crystals

The results of nematic liquid crystal - isotropic liquid phase transition study by the method of differential scanning calorimetry for inclusion compounds - mesoporous aluminosilicate molecular sieves of MCM-41 type (including Cu-exchanged samples) with encapsulated in inner-crystalline space nematic liquid crystal (5CB), as well as IR spectroscopic data for such compounds were represented. It was shown, that the 5CB molecules are able to interact with the active centers in the MCM-41 channels forming strong enough bonds of -C≡N⋅⋅⋅H-O- type. The relative amount of 5CB molecules interacting with the walls of channels and those retaining ‘liquid crystalline’ state in binary systems of molecular sieves MCM-41 and CuMCM-41 was estimated. This conclusion was confirmed by the data obtained from differential scanning calorimetry measurements. This revised version was published online in August 2006 with corrections to the Cover Date.     

Time-Resolved Spark-Source Mass Spectrometry; The Effect Of Spark Duration On Ion Intensity And Precision Of Analysis

Abstract

A radio-frequency probe and a synchronized electronic ion-beam chapper have been used to determine ion-intensity variation with spark duration. Large peaks in multiply charged ion intensities are detected in the early stages of the radio-frequency spark, while later in the spark period the singly charged species predominate. The effects of these variations on the precision of analysis have been determined. A gate was selected in the spark pulse, and a factor of two increase in precision was obtained.     

The Synthesis And Chemical Properties Of N-D-Pentopyranosylamines,Derivatives Of Tryptamine And Tyramine.

Abstract

The synthesis and structure of N-D-pentopyranosylamines derived from the amines tiyptamine tyramine and the pentoses D-xylose, D-arabinose and D-lyxose are presented. NMR spectroscopy and mass spectrometry were used to verify the proposed α,β-D-pentopyranosylamine structures.     

Extraction And Spectrophotometric Determination Of Cadmium Based On The Formation Of A Ternary Complex With Cadion And 1, 10-Phenanthroline

Abstract

Cadmium ion reacts with cadion and 1, 10-phenanthroline to form a 1:1:2 orange-red ternary complex in 0.5N sodium hydroxide medium. The complex is extracted by chloroform and has a molar absorptivity of 9.2 × 10⁴ l. mole^?1. cm^?1 at 490 nm. A method is developed for the determination of cadmium in electroplating waste water.     

Synthesis,Characterization, and Thermotropic Properties of Liquid Crystals with an Oligo (Ethylene Oxide) Monomethyl Substituent I: Biphenyl-Based Systems

New alkene liquid crystals 4-[oligo(ethylene oxide)_o, monomethylether)carbonyl]phenyl 4-[4(allyloxy) phenyl]benzoate(MBPBEn, n = 1-3), 4′-[oligo(ethylene oxide)_o, monomethylether)carbonyl]biphenyl-4-yl 4-[4-(al1yloxy)phenyl]benzoate(MBPBPEn, n = 1-3), (S)-4-[(2-methyl-I-butoxy)carbonyl]phenyl 4[4-(allyloxy)phenyl]benzoate(MBPBKA), and (S)-4′-[(2-methyl-l-butoxy)carbonyl]biphenyl-4-yl 4-[4(allyloxy)phenyl]benzoate(MBPBPKA) were synthesized and characterized using ¹H-NMR and elemental analysis methods. The thermal transition temperatures, mesomorphic properties, and mesophase textures of these compounds have been determined by differential scanning calorimetry (DSC), by polarizing optical microscopy, and by X-ray diffraction analysis. The effect of changes in chemical structure on the mesophase properties, mesophase and isotropic transition temperatures, and mesophase textures are discussed.     

层状液晶微环境对水杨酸铜配合物SOD样活性的影响

溶致液晶是表面活性剂分子形成的有序组合体,体系中的水相和有机相都是空间受限的微环境,这种特定的微环境对一些化学反应产生很大影响［１,２］．液晶体系也可用以模拟生物介质．人皮肤上老年斑的形成,就是由于超氧离子自由基Ｏ·－２在其中发生歧化反应生成的产物而引起的．为了更接近于生物环境,我们以水杨酸铜配合物作为ＳＯＤ模拟物,并把它歧化Ｏ·－２的反应移植到结构类似皮肤的层状液晶中来,探讨微环境对此歧化反应的影响．１　实验部分１．１　试剂与仪器　由水杨酸和乙酸铜按一般无机化合物合成方法制备了水杨酸－Ｃｕ（Ⅱ…     

Kinetic Determination Of Nitrite Based On The Griess Reaction And The Stopped Flow Technique

Abstract

A kinetic method for nitrite determination in solution is described. The method is based on the Griess reaction and the stopped-flow technique. The time between two preset levels of the output signal is used as a measure of the nitrite concentration. The determination involves only one step and is independet on the background absorption of the reagents. The working curve can be made with only 2 or 3 points. No blank value is shown. The method can be applied to dilute or(more) concentrated nitrite solutions by appropriate change of their pH. Concentrations as low as 1.10^?6M NO₂ ^? can be determined.     

曝光量对含香豆素基团的液晶共聚高分子的光控取向性能的影响

本文设计合成了含有香豆素光敏基团的单体4-(6-丙烯酰氧基己氧基)苯甲酸-7-羟基香豆素酯(M1)和一种只含液晶基元的单体4-(丙烯酰氧基)己基苯甲酸-4-甲氧基苯酚酯(M2),并将这两种单体进行自由基聚合得到了共聚物.当该聚合物薄膜置于线性偏振紫外光(LPUV)下,会发生轴选择性的光化学反应,利用动态紫外光谱(UV光谱),对所合成的共聚物的光化学性能进行了研究.结果表明:当曝光能量为1740 mJ/cm²时,光反应达到饱和,紫外吸光度将不随曝光能量的变化而变化;随着曝光能量的增加,聚合物在反应初期光反应速率比较大,当曝光能量达到500 mJ/cm²左右,光反应度已经超过50%;当曝光量达到324 mJ/cm²,各向异性ΔA达到最大,ΔA_max=0.039.     

Effect Of Iridium Addition On The Reducibility Of MoO3/Alumina Catalyst

The reducibility of oxidic MoO₃/alumina catalyst modified by different amounts of Ir was studied by temperature-programmed reduction. Ir facilitated the reduction of both polymeric Mo_oct and isolated Mo_tet species. However, the interaction of Mo_tet with Ir particles smaller than 0.8 nm inhibited reduction, probably because of formation of a non-reducible Ir-O-Mo phase.     

Effect of Epoxidation of Carbocyclic Double Bonds on Conformational Flexibility of 1(10)E,4E-Germacranolides

The effect of substitution of double bonds by epoxy groups in 1(10)E,4E-germacranolides is studied by molecular mechanics. The probabilities of forming conformers in the epoxy derivatives are determined. Barriers to possible conformational transitions are estimated     

Effect Of The Preparation Method On The Dispersion Of Metallic Particles In Rh/Tio2 Systems

In Rh/TiO₂ systems, the dispersion of Rh particles depends on the reduction temperature and on the preparation method. The capacity for H₂ adsorption is larger for those samples reduced at low than at high temperature.