A review of: “Liquid Crystal Dispersions”

Abstract

Paul Drzaic, World Scientific, 1995, ISBN 981 02 1745 5     

Tuning of a Dye Laser By a Liquid Crystal†

We describe how a cholesteric liquid crystal device can be used in a laser cavity to induce tuning of the laser line. Tuning of the order of 10Å is obtained by applying low voltages to the liquid crystals film. The problems, the advantages and the feasibility of the method is discussed, reporting several experimental data.     

Effect of Particle Size on Electro-Optic Properties of Liquid Crystal Devices Doped with γ-Cyclodextrin Stabilized Barium Titanate Nanoparticles

Barium titanate stabilized by γ-cyclodextrin nanoparticles were prepared by using a microwave reactor equipped with ultrasonic nozzle mixing at 240°C in a tetraethylene glycol solution of barium ethoxide and titanium ethoxide in the presence of γ-cyclodextrin. Particles in γ-cyclodextrin-stabilized BaTiO₃ nanoparticles had an average diameter of 2.1 nm and mainly distributed within the range of about 1 to 4 nm. The γ-cyclodextrin-stabilized BaTiO₃ nanoparticles were mixed with 4-cyano-4′-pentylbiphenyl at room temperature resulting in a liquid crystal sol of 4-cyano-4′-pentylbiphenyl. The response time of liquid crystal devices in the presence of γ-cyclodextrin-stabilized BaTiO₃ nanoparticles was faster than that in the absence.     

Crystal structure of 5-(2′-aminophenyl)-2-dimethylamino-1,3,4-thiadiazole

The crystal structure of 5-(2′-Aminophenyl)-2-dimethylamino-1,3,4-thiazole is determined by X-ray diffraction. The compound is prepared by an unusual recyclization of 3-N, N-dimethylthioureidoquinazolin-4(3H)-one. The crystal is monoclinic, space group P2₁/c, a = 7.420(2) Å, b = 10.466(5) Å, c = 14.752(9) Å, β = 109.2(4)°, ρ_calcd = 1.359 g/cm³, and Z = 4 for the C₁₀H₁₂N₄S composition. The molecule consists of the thiadiazole and phenyl rings and the dimethylamine N(CH₃)₂ and amine NH₂ groups attached to the rings. The molecule as a whole is planar. The dihedral angle between the rings is 8.9°. The N(1) and N(4) atoms in the molecule are bound through the intramolecular interaction (2.76 Å). Molecules, which are linked in pairs by antiparallel hydrogen bonds, form a framework structure.     

Interlayer Reaction of Polyamine/α-Zirconium Phosphate Intercalation Compounds with Some Aldehydes

Abstract

The intercalation compound between α-zirconium phosphate and N,N′-bis-(3-aminopropyl)-1, 3-propanediamine has two different modifications with respect to the conformation of the guest amine molecules: one is “bent form” and the other “straight form”. Reactivity of each phase with a series of aldehydes was examined. ¹³C CP/MAS NMR indicated that the tetraamine reacts stereoselectively with aldehydes to form cis-imine in the interlayer spacing. Depending on the molecular size of aldehyde, it is found that a significant difference can be recognized in the yields of the imine products for the two phases of intercalation compounds. It is also noted that residual water molecules in the interlayer spacing play an important role in the imine formation reaction.     

A Comparison of the High Resoluton Crystal Structures of the π- Molecuar Complexes of Anthracene and Phenothiazine with Pyromellitic Dianhydride

The π-molecular complexes formed by aromatic molecules with three rings tend to form crystals of high purity and are therefore ideal for solid state spectroscopic and photocurrent studies. We have therefore undertaken an investigation of the detailed structures of a number of such complexes in order to facilitate the interpretation of such data and other physical properties and in order to better understand the large changes in physical properties generated by small changes in composition and molecular packing. The piezoreflection spectra of the anthracene-pyromellitic dianhydride complex (A-PMDA) has been studied by Eckhardt and Merski (1973). The photo-current excitation spectra of A-PMDA was reported by Karl and Ziegler (1975) and more recently the preparation, optical properties, absorption and photoconductivity properties of phenothiazine-pyromellitic dianhydride have also been studied. (Anthonj, Karl, Robertson and Stezowski, 1979).     

Crystal and molecular structure of 2-(2′-chloro-5′-nitrostyryl)benzoselenazole

The title compound C₁₅H₉ClN₂O₂Se (nsbse) is orthorhombic, witha=6.823(2),b=7.860(2),c=26.349(5) Å,Z=4,D _x =1.709,(MoK)=28.3 cm^–1,F(000)=720,T=298K in space groupP2₁2₁2₁. The structure was solved by heavy atom and Fourier methods and refined toR=0.045 for 1095 unique observed reflections. The molecule is almost planar, with a dihedral angle of 4.8(2)° between the benzoselenazole and phenyl rings. The C-Se-C angle in the selenazole ring is very small, 84.6(4)°, while the C-N-C angle in that ring is 113.7(7)°.     

Synthesis and Evaluation of Liquid Crystal Behavior of a Novel Homologous Series: 4-(4′-n-Alkoxy benzoyloxy) Phenylazo-2″, 6″-dimethylbenzenes

A novel homologous series entitled 4-(4′-n-alkoxy benzoyloxy) phenyl azo 2^″, 6^″-dimethyl benzenes consisting of 12 members is reported. Liquid crystal behavior as a nematogenic mesophase commences from the pentyloxy homologue monotropically and then continues enantiotropically until the last hexadecyloxy homologue without exhibition of any smectogenic behavior. An odd-even effect is observed for nematic-isotropic transition curve of the phase diagram. The textures of the nematic mesophase are of the threaded or Schlieren type. Analytical and spectral data support the molecular structure of the homologues. Transition temperatures of the novel homologues were determined by an optical polarizing microscopy. Liquid crystal properties of a novel homologous series are compared with other known homologous series. The average thermal stability for the nematic phase is 77.1°C.     

Crystal and molecular structure of 2,6-dimethyl-3-acetyl-5-carbomethoxy-4- (4′-methoxyphenyl)-1,4-dihydropyridine

2,6-Dimethyl-3-acetyl-5-carbomethoxy-4-(4-methoxyphenyl)-1,4-dihydropyridine has been synthesized and characterized by X-ray diffraction analysis. The compound crystallizes in the monoclinic space group P2 ₁/c with cell parameters a=16.085(2) Å, b= 12.332(3) Å, c= 8.479(4) Å, = 99.23(8)°, Z=4. The structure exhibits both intra and intermolecular hydrogen bonds. The structure adopts a flat boat conformation in the dihydropyridine ring.     

Crystal structure of 5-fluoro-1-(2,3,6-trideoxy-α-l-glycero-hex-2-enopyranos-4-ulosyl)uracil

The present compound crystallizes in the space groupP2₁2₁2₁ withZ=4 and cell parametersa=21.687(2),b=8.155(3),c=5.883(2)Å. The structure was solved by direct methods and refined by full-matrix least-squares to a finalR value of 0.045 for 1153 observed reflections. The N-glycosidic torsion angle _CN is in the anti-range and the pyranosyl ring adopts a distorted half-chair conformation with ₂=142.7(4)°, ₂=124.4(3)° andQ=0.456(2)Å. In the crystal packing the molecules are linked together by N-HO hydrogen bonds and C-HO contacts.     

Two similar lactone-hydrochlorides with different types of hydrogen bonding networks: Crystal structure of (R,S)-α-amino-γ-caprolactone hydrochloride and racemic α-amino-γ-methyl-γ-valerolactone hydrochloride semihydrate

The X-ray crystal structure of (R,S)--amino--caprolactone hydrochloride (compound1) and -amino--methyl--valerolactone hydrochloride semihydrate (compound2) are presented. Both compound1 and compound2 belong to the orthorhombic system. Caprolactone-hydrochloride1 crystallizes in the space groupP2₁2₁2₁ witha=5.1948(7),b=8.7404(8),c=17.907(1) Å.V=813.0(2) ų,Z=4. Valerolactone-hydrochloride2 crystallizes in the space groupP na2₁ witha=26.771(8),b=5.1598(7),c=13.201(3) Å,V=1823.5(7) ų,Z=8. The lactone cations maintain the same, open envelope conformation in both crystals. The lactone-hydrochloride packing arrangements in1 and2 are distinctly different. While in1 N–H...Cl and N–H...O hydrogen bonding creates two dimensional nets in the form of puckered layers perpendicular to the [001] direction, in2 a water molecule of crystallization with an additional OW–H...Cl hydrogen interaction assists in forming a three-dimensional hydrogen-bond network throughout the crystal.     

Preparation of the Crystal Complex of Phosphopantetheine Adenylyltransferase from Mycobacterium tuberculosis with Coenzyme A and Investigation of Its Three-Dimensional Structure at 2.1-Å Resolution

Crystallography Reports - Recombinant phosphopantetheine adenylyltransferase from Mycobacterium tuberculosis (PPAT Mt), which was produced by a high-producing strain and purified to 99%, was used...     

Crystal structure of 2,5-cyclohexadien-4-one-spiro-3′-(2′-methylthio-5′,5′-dimethyl-1′-pyrroline)

The crystal structure of the pyrrole derivative 2,5-cyclohexadien-4-one-spiro-3′-(2′-methylthio-5′,5′-dimethyl-1′-pyrroline) is determined by X-ray diffraction. Two independent molecules have similar structures and close geometric parameters but differ in configuration of the pyrrole ring and orientation of the thiomethyl group with respect to the pyrrole ring.     

Synthesis of 7,4′-Bis-(hydroxyl)-8,3′,5′-tris-(hydroxymethyl)isoflavone and Crystal Structure of its Ester

Abstract 7,4′-bis-(hydroxyl)-8,3′,5′-tris-(hydroxymethyl)isoflavone (I) and its ester were synthesized and examined by IR, element analysis and ¹H NMR. The crystal of 7,4′-bis-(acetyl oxide)-8,3′,5′-tris-(acetoxymethyl)isoflavone (II) was studied by X-ray diffraction. (II) crystallizes in the monoclinic with space group P2 ₁ /c. a = 17.987(3) ?, b = 17.972(3) ?, c = 8.4087(11) ?, β = 97.703(3)°, V = 2693.7(6) ?³ and Z = 4. The molecular structure of the ester consists of a benzopyranone moiety, a phenyl moiety, two acetyl oxides and three acetoxymethyl groups. Hydrogen bonds and aromatic stacking interactions link the ester into a two-dimensional structure. Index Abstract 7,4′-bis-(hydroxyl)-8,3′,5′-tris-(hydroxymethyl)isoflavone and its ester were synthesized and examined by IR, element analysis and ¹H NMR. The result of the ester’s crystal structure showed that hydrogen bonding and aromatic π–π stacking assemble the ester into a two-dimensional networking structure.      

Synthesis and Liquid Crystal Behaviour of Further 4,4″-Disubstituted 2'-Fluoro-1,1':4',1”-Terphenyls

Further to earlier work on the liquid crystal properties of fluoro-1,1':4',1”-terphenyls¹ we have now extended this series to include terminally fluoro-and cyano-substituted 2'-fluoro-1,1':4',1″-terphenyls, chiral 2'-fluoro-1,1':4',1″-terphenyls, and esters derived from 2'-fluoro-1,1':4',1”-terphenyls and incorporating the alkylcyclobutyl group. The preparations and transition temperatures for these series of compounds are presented and their transition temperatures and mesophase types are discussed. An interesting result from this work was the appearance of an S^* _C phase for one chiral homologue and of S _c phases for the esters incorporating the alkylcyclobutyl group. The S _c formation is attributed to the presence of the fluoro-substituent.

Keywords: terphenyls, fluoroterphenyls, smectic C phases, cyclobutyl esters     

Crystal structure of an analog of the anticonvulsant lamotrigine, 3,5-diamino-6-(2,3,5-trichlorophenyl)-1,2,4-triazine·dimethanolate, and structure comparisons with related analogs

The compound 3,5-diamino-6-(2,3,5-trichlorophenyl)-1,2,4-triazine crystallizes with two methanol solvent molecules in the triclinic space group P1¯, with a = 7.372(4), b = 10.476(4), c = 11.863(11) Å, = 72.18(5), = 79.73(6), = 79.47(4)°. There is substantial distortion between the phenyl and triazine rings as illustrated by the value of the nonbonded angle C3t—C6t—C4 of 173.60° and the C4 atom being –0.4487 Å from the plane calculated for the triazine ring atoms. The lengths of the bonds of the triazine moiety suggest that there is a potential decrease in the degree of aromaticity of the ring. Comparisons are made between this structure, and other lamotrigine analog structures that have been reported.     

Magnetic and transport studies of σ-phase Fe50V50 alloys with different thermal history

The influence of the formation conditions of the sigma phase in an equiatomic FeV alloy on the magnetic and electric transport properties is studied. It is found that a sigma phase sample with higher resistivity (subject to a previous long annealing) has a much sharper magnetic transition than one formed after a shorter heat treatment and quenching, although both have very similar magnetic moments and ferromagnetic transition temperatures (T_c ～ 15 K from minimum dM/dT).