“Polyaniline”: Interconversion of Metallic and Insulating Forms

Abstract

“Polyaniline” has been synthesized in various forms both chemically and electrochemically in aqueous media. The qulnoid-benzenoid-diimine form, an insulator, is doped by dilute aqueous protonic acids to the metallic regime ([sgrave] = 5 ohm^?1cm^?1; compressed pellet) to give the corresponding iminium salt. This represents a new type of p-doping phenomenon in a conducting polymer. Both these forms are stable in the presence of air and/or water. The doping process is reversed by treatment with aqueous alkali. Cyclic voltammetry studies in an aqueous electrolyte show excellent reversibility between selected reduced and oxidized forms of polyaniline.     

New chiral metal-mesogenic nanosystems “silver - thiocholesterol” and their adsorption properties

ABSTRACT

New chiral matrices for thin film chromatography were obtained using hybrid metal-mesogenic nanosystems «silver – thiocholesterol» with different metal to ligand ratio, immobilized on silica gel particles. It was shown, that heteroatomic derivative of cholesterol – thiocholesterol and its composition with small silver nanoparticles formed in the system by the chemical reduction of silver ions possess liquid crystalline cholesteric mesophase. Molar ratio between thiocholesterol ligand molecules (L) and silver (Ag) insignificantly influenced on the size of silver nanoparticles formed in the system: for molar ratio Ag : L = 1:5 the main diameter of nanoparticles was equal to (2,7 ± 0,4) nm, for molar ratio Ag : L = 1:2 – (2, 2 ± 0,4) nm, for molar ratio Ag : L = 1:0,5 – (2,1 ± 0,6) nm. The new chiral matrices for thin film chromatography possess enantioselectivity related to optical isomers of 2,2′-diamino-1,1′-binaphtol (DABN) and trifluoroantranylethanol (TFAE). We have succeeded to select optical isomers of TFAE with selecting factor equal to 1,56.     

Optical and Electrooptical Properties of “Guest-Host” Effect in Twisted Liquid Crystal Layers

Abstract

Optical and electro-optical characteristics of a positive dichroic dye-doped Twisted Nematic Liquid Crystal Layer (TNLCL) for two different orientations of the input light polarization to the NLC director α (α = 0°, α = 90°) and various NLC optical path lengths A = Δnd/λ (Δn = real part of birefringence, d = cell thickness, λ = wavelength) are investigated. In the case of one polarizer, the maximum contrast ratio is obtained for A ? 1.2 (α = 0°) and A ～ 0 (α = 90°), regardless of whether Δn or d is changed. The viewing characteristics of a dye doped TNLCL with one polarizer are shown to be more uniform than those for a “pure” TNLCL between parallel polarizers.     

Synthesis and UV photoelectron investigation of the “peptide units” of α,β-dehydroamino acids

The He(I) and He(II) photoelectron (PE) spectra of the N-methylamides of N-acetyldehydroalanine (1) and N-acetyldehydrophenylalanine (2) are presented and discussed, within a comprehensive investigation of the electronic structure and conformation of, -dehydroamino acid derivatives. Three different procedures have been adopted for the synthesis of1. The PE results of the peptide units are in tune with theoretical predictions and they support the view that in the vapor phase the tendency towards a planar arrangement around the torsion angle is much more marked for N-acetyldehydroalanine-NHR systems than for (Z)-substituted ones.     

Editorial board page for “Molecular Crystals and Liquid Crystals”, Volume 273, Number 1

Abstract

This is a scanned image of the original Editorial Board page(s) for this issue.     

Synthesis and mesomorphic properties of a new series of triazole bent-core liquid crystalline molecules by “click” reaction

The synthesis and mesomorphic properties of new triazole liquid-crystalline are presented and discussed. These triazole derivatives have been synthesized by reacting 4-hydrazoic iodobenzene with the 4-alkyl phenyl acetylene in dimethyl formamide (DMF). The molecular structure is characterized by 1H NMR, Fourier transform infrared spectroscopy (FTIR), time-of-flight mass spectrometry (TOF-MS) and the mesomorphic properties are characterized by polarizing optical microscope (POM) and (DSC). These new triazole liquid-crystallines have higher melting point and clearing point and the final compounds display both nematic and smectic liquid-crystalline phases.     

Gel growth of α and γ glycine and their characterization

The microbial free single crystals of α and γ glycine were grown from gel at room temperature in a new chemical route. These crystals showed a superior quality than the solution grown crystals. The metastable α-form and the stable γ-form of glycine were crystallized in silica gel by solubility reduction method. The form of crystallization is confirmed by single crystal and powder X-ray diffraction analyses. The crystals of α and γ glycine were found to crystallize in monoclinic and hexagonal crystal systems, respectively. For analyzing the functional group and thermal stability of α and γ glycine crystals, spectroscopic and thermal analyses have been carried out. The dielectric studies were performed to find the dielectric constant of the grown crystals and the results are discussed. Second harmonic generation efficiency of the crystal was measured by Kurtz’s powder method using Nd:YAG laser and it was found to be 2.68 times that of potassium dihydrogen phosphate crystals.     

“微距升华”晶体生长方法

随着功能器件向微型化发展,微纳米尺度的低维晶体成为构建新一代功能器件的材料基础。传统的体块单晶生长方法不适用于低维晶体。长久以来,对新型低维材料的研究依赖于机械剥离、溶液法和化学/物理气相沉积等方法,这些方法在效率、可控性和适用性等方面存在诸多限制,因此发展高效可控的低维晶体新型生长方法成为实现这些低维材料器件实用化的前提。山东大学晶体材料国家重点实验室陶绪堂、刘阳团队基于多年来在分子材料结晶基础方面的研究成果,发明了新的“微距升华”低维晶体生长方法。“微距升华”法利用原料与生长衬底之间的微小间距,可以在常压下实现常规物理气相传输中需要高真空才能够达到的分子流传输模式,使生长过程不再受传质限制,因此微距升华法无须真空和载气,速度快,原料利用率接近100%。该方法适用于大部分的有机半导体、金属配合物,甚至含有大量羧基、羟基的药物分子及熔点在一定范围内的无机物晶体,生长的微纳米晶体与电子器件制程匹配,屡次创新器件迁移率记录。新方法受到业界广泛关注,已被多国科学家采用。     

Synthesis and crystal and molecular structure of newN-substituted γ-hydroxybutyramides

TheN-(2-phenylethyl)amide of-(1, 1-ethylenedioxy)-ethyl--hydroxybutyric acid (II) and theN-(p-methoxybenzyl)amide of-(1, 1-ethylenedioxy)-ethyl--hydroxybutyric acid (III) have been synthesized and the crystal structure ofIII has been solved. CompoundIII, C₁₆H₂₃O₅N, crystallizes in the monoclinic space groupP2₁/c witha=12.572(2),b=11.149(2),c=12.317(2) Å and=106.53(1)°. The structure was solved by direct methods, and refined by full-matrix least squares to giveR=0.040 (R _w =0.047) for 2004 intensities. The dioxolane ring has a deformed half-chair conformation.     

Ground state structures of molecules “prepared” for phototautomerization: 2,2′-bipyridyl-3,3′-diol and 2,2′-bipyridyl-3-ol

The crystal structures of two molecules undergoing fast intramolecular excited state proton transfer (2,2-bipyridyl-3,3-diol, BP(OH)₂, and 2,2-bipyridyl-3-ol, BP(OH)) are reported and compared with the results ofab initio and molecular mechanics calculations. Strong intramolecular hydrogen bonding is observed in both cases. The pyridyl rings are coplanar in BP(OH)₂, whereas in BP(OH) they form an angle of 3.7°.Dedicated to Prof. R. Zahradnik on the occasion of his birthday.     

Comments on “Kinetics of non-isothermal crystallization and glass transition phenomena in Ga10Se87Pb3 and Ga10Se84Pb6 chalcogenide glasses by DSC” by Al-Agel et al.

A critical review of a recent paper by Al-Agel et al. (J. Non Cryst. Solids, 358 (2012) 564) on kinetics of non-isothermal crystallization and glass transition phenomena in Ga₁₀Se₈₇Pb₃ and Ga₁₀Se₈₄Pb₆ chalcogenide glasses is presented. A number of possible errors in procedures have been noticed. In particular, X-ray diffraction, Differential Scanning Calorimetry and Field Emission Scanning Electron Microscopy data may have been misinterpreted. Kinetic parameters deduced from data derived from the DSC results and using approaches developed by Kissinger, Ozawa and Matusita and others are discussed. Activation energies and Avrami exponents have been re-calculated from the experimental data presented by Al-Agel et al.     

Structural and magnetic properties of ZnO and Zn1−xMnxO nanocrystals

Chemical precipitation of metal-ions from aqueous solution has been successfully used to produce Zn_1?xMn_xO nanocrystals, in the form of nano-powder. X-ray diffraction (XRD) measurements reveal that the as-prepared samples are single-phase materials and their lattice constant changes with the variation of Mn-concentration, which indicates the incorporation of Mn²⁺ into the hosting ZnO. These findings are corroborated by the observation of the well defined six hyperfine lines of Mn²⁺ ion in the electron paramagnetic resonance (EPR) spectra of the samples with a low Mn-concentration, and of a broad EPR line, which manifests the onset of Mn–Mn exchange interaction, in the samples with an elevated value of x.     

Synthesis of spinacine and spinacine derivatives: crystal and molecular structures of Nπ-hydroxymethyl spinacine and Nα-methyl spinaceamine

The natural amino acid L-Spinacine (4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine-6-carboxylic acid) has been synthesized following a new pathway which gives a chemically and optically pure product with an excellent yield. The crystal structures of a synthetic intermediate, N^π-hydroxymethyl-spinacine, and a spinacine derivative, N^α-methyl-spinaceamine, have been investigated through X-ray diffraction: Spi(πMeOH)·H₂O, monoclinicP2 _i,a=8.571(1),b=6.682(1),c=8.588(1) Å, and β=94.67(1)^o. Spm(αMe)·2HCl·H₂O, triclinicP l,a=7.492(4),b=10.799(3),c=7.040(2) Å, α=91.88(2), β=98.36(3) and γ=73.34(3)^o. Spi(πMeOH) crystallizes with a water molecule and displays a zwitterionic character. The carboxylate group is in equatorial position and forms a short electrostatic interaction of 2.618(2) Å between one of its oxygens and the protonated nitrogen of the tetrahydropyridine ring. The crystal packing is assured by strong O?H???O, O?H???N, N?H???N intermolecular hydrogen bonds and C?H???O close contacts. The biprotonated compounds Spm(αMe) crystallizes with two Cl^? anions and a water molecule. The positive charge on the imidazole ring is delocalized on the conjugated moiety N=C?N. The crystal is built up by clusters formed by two biprotonated Spm(αMe) molecules, four Cl^? anions and two water molecules linked together by hydrogen bonds.     

11th Conference on Solid and Liquid Crystals—Material Science and Applications

Abstract

The eleventh conference in a series of biennial meetings was organized by Professor Jozef Zmija group from the Institute of Technical Physics WAT, Warsaw, Poland. It was supported by the State Committee of Scientific Research (KBN), the Polish chapter of the International Society for Optical Engineering (SPIE) and the Committee of Crystallography, Polish Academy of Sciences. These conferences have become more international, and this meeting, organized just outside Zakopana, in the Tatra mountains attracted more than 210 scientists, 51 from abroad.