Mesomorphic phase transitions and electro-optical properties of benzyl fluoroalkyl thioether liquid crystalline compounds

Four series of liquid crystalline (LC) compounds containing benzyl perfluoroalkyl thioether groups (BFT), 4-n-alkoxyphenylbenzyl perfluoroalkyl thioethers (nO-BBFT-FmF), 4-n-alkoxyphenylbenzyl perfluoroisoalkyl thioethers (nO-BBFT-FmIF), 4-n-propylcyclohexylbenzyl perfluoroalkyl thioethers (3-C1BFT-FmF) and 4-ethylcyclohexyl-3'-fluorobenzyl perfluoroalkyl thioethers (2-C1FBFT-FmF), were synthesized and their mesomorphic phase transitions and electro-optical properties investigated. nO-BBFT-FmF and nO-BBFT-FmIF have SmA, SmB and CrE phases, while 3-C1BFT-FmF and 2-C1FBFT-FmF showed a SmB phase. It was found that the appearance of a LC phase and the thermal stability were closely connected with the chemical structures of the rigid core part and the terminal groups. The electrooptical properties were investigated for BFT using ZLI-1132 as nematic solvent. Some of the BFT compounds have a good solubility of 15 wt % in ZLI-1132 and can be used as a component for lowering the refractive anisotropy (Delta n) of the host ZLI-1132 solvent.     

Mesomorphic phase transitions and electro-optical properties of benzyl fluoroalkyl ether derivatives

Three series of liquid crystalline (LC) compounds containing benzyl fluoroalkyl ether groups (BFE), 4-n-propylbicyclohexylbenzyl fluoroalkyl ethers (3-C2BFE-X,X: fluoroalkyl group), 4-n-alkylcyclohexylbenzyl fluoroalkyl ethers (m-C1BFE-X, m: carbon no. ofn-alkyl group)and 4-n-alkoxyphenylbenzyl fluoroalkyl ethers (mO-BBFE-X), were newly synthesized for several fluoroalkyl groups (X) such asn-fluoroalkyl, branched fluoroalkyl, and 2-perfluoropropoxy-2,3,3,3-tetrafluoropropyl. The mesomorphic phase transitions and electro-optical properties were investigated for BFE. 3-C2BFE-X and m O-BBFE-X have SmB phases, and SmA and/or E phases, respectively, while m-C1BFE-X showed no mesophases. The occurrence and thermal stability of the LC phases are related to the chemical structures of the rigid core part and the terminal groups. The electro-optical properties were investigated for 15 wt% of BFE in host ZLI-1132. It was found that the BFE compounds have a good solubility of more than 15 wt% in ZLI-1132 and can be used as a component for lowering the refractive anisotropy of the host ZLI-1132 solvent.     

Preliminary communication Electro-optical properties of benzyl fluoroalkyl ether derivatives

Several new fluorinated liquid crystal compounds, 4- n -propylbicyclohexylbenzyl fluoroalkyl ethers (C2BFE) and a 4- n -propylcyclohexylbenzyl 2-perfluoropropoxy-2,3,3,3-tetrafluoropropyl ether (C1BFE), were synthesized and their phase transition behaviours and electro-optical properties investigated by DSC, polarizing optical microscopy, Abbe refractometry and other physical methods. All the C2BFE compounds showed a layered mesophase like SmB, while C2BFE had no mesophase. All the fluorinated compounds have good solubility in ZLI-1132 (more than 15 wt %) and can be used as a component for lowering the refractive anisotropy (Delta n ) of the nematic solvent ZLI-1132.     

Effects on molecular orientation and phase transition of addition of carbon nanotubes into liquid crystalline matrix

For practical guest–host applications, it is important to choose dyes with a high ability of orientation in the liquid crystal (LC) matrix. In this experimental work, two different azo-structured dyes (disperse yellow 3 and 7) were separately doped to each of two different nematic LCs (E7 and ZLI-1132). Their solubilities, textures, phase transition temperatures and order parameters were determined. At the second stage, single-walled carbon nanotubes (SWCNTs) in a small amount were separately added to each of these solutions, and the experiments were repeated as similar to the previous ones. The solubilities of dyes in the LC E7 were lower than those of ZLI-1132. Moreover, the highest order parameter value was attained with yellow 7 dye in ZLI-1132 nematic host. Co-use of nanoparticles (CNTs) as dopant resulted in notable increases in order parameters. These dyes and CNTs did not significantly destabilise the mesomorphic phase of nematic hosts. An appreciable change in textures was not monitored with addition of dopant(s). In addition, it was observed that the narrowing on the temperature range of the LC did not take place with the addition of dopants to the crystal; on the contrary, an increase was recorded.     

Unveiling the Role of Hydrogen Bonds in Luminescent N-Annulated Perylene Liquid Crystals

We report the liquid-crystalline (LC) and luminescent properties of a series of N-annulated perylenes ( 1 – 4 ) in whose molecular structures amide and ester groups alternate. We found that the LC properties of these compounds not only depend on the number of hydrogen-bonding units, but also on the relative position of the amide linkers in the molecule. The absence of amide groups in compound 1 leads to no LC properties, whereas four amide groups induce the formation of a wide temperature range columnar hexagonal phase in compound 4 . Remarkably, compound 3 , with two amide groups in the inner part of the structure, stabilizes the columnar LC phases better than its structural isomer 2 , with the amide groups in the outer part of the molecule. Similarly, we found that only compounds 1 and 2 , which have no hydrogen bonding units in the inner part of the molecule, exhibit luminescence vapochromism upon exposure to organic solvent vapors.     

聚｛11-[(4′-正庚氧基-4-联苯基)羰基]氧-1-十一炔｝的相结构与相转变

采用示差扫描量热法(DSC)、一维(1D)、二维(2D)广角X-射线衍射(WAXD)和偏光显微镜(PLM)等研究手段对聚{11-[(4′-正庚氧基-4-联苯基)羰基]氧-1-十一炔}(PA-9,7)的本体相转变和相结构进行研究,并采用分子动力学方法对相结构进行模拟.结果表明,样品的相转变为近晶B相(SmB)近晶A相(SmA)各向同性态(Iso).在近晶B相中,侧链在层状结构中排列成具有六次对称性的准长程有序结构。     

Bis-chelated imine-alkoxytitanium complexes: novel chiral dopants with high helical twisting power in liquid crystals

Enantiomerically and diastereomerically pure bis-chelated imine-alkoxytitanium complexes 6 and 7 have been synthesized and used as chiral dopants for converting nematic into cholesteric phases. The dopants were tested in mainly commercially available nematic liquid crystalline compounds or mixtures: LC1 (BASF), ZLI-1695 and ZLI-1840 (Merck), as well as N-(4-methoxybenzylidene)-4'-butylaniline (MBBA). The values of the helical twisting power (HTP) were determined by the Grandjean-Cano method. Exceptionally high helical twisting powers were obtained. Thus, the titanium complex 6 h displayed a HTP value of 740 microm(-1) in MBBA, the highest HTP value reported. The helical twisting power has been found to depend strongly on the structure of the nematic phase and the substitution pattern of the chiral ligand in the titanium complexes 6 and 7. Crystal structure analysis of 6 f confirmed the A,R,R configuration of the metal complex. The chiral imine ligands 4 and 5 were derived from the regioisomeric amino alcohols 1 and 2.     

delta-[Ru(acac)(2)L] (L = a mesogenic derivative of bpy) as a novel chiral dopant for nematic liquid crystals with large helical twisting power

The helical twisting power of a chiral ruthenium complex Delta-[Ru(acac)2L], in which L (mesogenic ligand) and acac denote 5,5'-(4-octylphenyloxycarbonyl)-2,2'-bipyridyl and acetylacetonate, respectively, was determined to be betaM = -71 and -1.8 x 102 mum-1 in room-temperature nematics ZLI-1132 and MBBA, respectively.     

Thermally stable perfluoroalkylfullerenes with the skew-pentagonal-pyramid pattern: C60(C2F5)4O, C60(CF3)4O, and C60(CF3)6

Reaction of C(60) with CF(3)I at 550 degrees C, which is known to produce a single isomer of C(60)(CF(3))(2,4,6) and multiple isomers of C(60)(CF(3))(8,10), has now been found to produce an isomer of C(60)(CF(3))(6) with the C(s)-C(60)X(6) skew-pentagonal-pyramid (SPP) addition pattern and an epoxide with the C(s)-C(60)X(4)O variation of the SPP addition pattern, C(s)-C(60)(CF(3))(4)O. The structurally similar epoxide C(s)-C(60)(C(2)F(5))(4)O is one of the products of the reaction of C(60) with C(2)F(5)I at 430 degrees C. The three compounds have been characterized by mass spectrometry, DFT quantum chemical calculations, Raman, visible, and (19)F NMR spectroscopy, and, in the case of the two epoxides, single-crystal X-ray diffraction. The compound C(s)-C(60)(CF(3))(6) is the first [60]fullerene derivative with adjacent R(f) groups that are sufficiently sterically hindered to cause the (DFT-predicted) lengthening of the cage (CF(3))C-C(CF(3)) bond to 1.60 A as well as to give rise to a rare, non-fast-exchange-limit (19)F NMR spectrum at 20 degrees C. The compounds C(s)-C(60)(CF(3))(4)O and C(s)-C(60)(C(2)F(5))(4)O are the first poly(perfluoroalkyl)fullerene derivatives with a non-fluorine-containing exohedral substituent and the first fullerene epoxides known to be stable at elevated temperatures. All three compounds demonstrate that the SPP addition pattern is at least kinetically stable, if not thermodynamically stable, at temperatures exceeding 400 degrees C. The high-temperature synthesis of the two epoxides also indicates that perfluoroalkyl substituents can enhance the thermal stability of fullerene derivatives with other substituents.     

Etude en RMN: Couplages a Longue distance dans les Perfluoro-alkyl-1 Dihydro-3,4 Isoquinoléines et Perfluoro-alkyl-1 Isoquinoléines

The ¹H and ¹⁹F NMR spectra of 1-(perfluoroalkyl)-3,4-dihydroisoquinolines and 1-(perfluoroalkyl)isoquinolines have been investigated. Several long distance couplings were observed: the α-fluorine atoms of the perfluoroalkyl chains exhibit in the 1-(perfluoroalkyl)-3,4-dihydroisoquinolines homoallylic coupling with the methylenic protons in position 3, and in the 1-(perfluoroalkyl)-4-methylisoquinolines interbenzylic coupling with the methyl groups in 4, respectively. Furthermore the α-fluorine atoms of the perfluoroalkyl chains are, in all the compounds, coupled with the H-8 proton. To our knowledge, this is the first time that such a ⁵J coupling of an aromatic proton and a fluorine atom has been demonstrated. The various long distance couplings are interpreted using geometric, steric and electonic effects.     

Hole mobility and lifetime in a smectic liquid crystalline photoconductor of a 2-phenylnaphthalene derivative

We have investigated hole transport properties in the smectic mesophases of a 2-phenylnaphthalene derivative 6-(4'-octylphenyl)-2-dodecyloxynaphthalene in detail by using time-of-flight technique. The transient photocurrents were measured in liquid-crystal cells with various thickness from 5 to 700 microm. They were well defined and nondispersive in the smectic A (SmA) phase up to 500 microm and in the smectic B (SmB) phase within the entire thickness employed, while they exhibited an exponential decay in the SmA phase at 700 microm. The mobilities in the SmA and SmB phases were constant in each mesophase irrespective of the cell thickness, and were 2.5 x 10(-4) and 1.7 x 10(-3) cm2V s, respectively. The hole lifetimes were determined to be 10 ms and longer than 5 ms for the SmA and SmB phases, respectively. We discuss the origin of these lifetimes from the two points of view, i.e., hole trapping by a trace amount of existing impurities and recombination with negative ionic charges. We conclude that impurities are mainly responsible for the present hole lifetime test.     

Determination of sugar compounds in atmospheric aerosols by liquid chromatography combined with positive electrospray ionization mass spectrometry

We here report a method for the determination of sugar compounds of known presence in atmospheric aerosols using liquid chromatography (LC) combined with positive electrospray ionization mass spectrometry (MS). The target analytes include C(3)-C(6) monosaccharide alcohols (glycerol, erythritol, xylitol, mannitol), C(5)-C(6) monosaccharides (xylose, glucose, and levoglucosan), a disaccharide (sucrose), and a trisaccharide (melezitose). A mobile phase consisting of 20% 10 mM aqueous ammonium acetate, 8% methanol, and 72% water was found to provide abundant [M+NH(4)](+) adduct ions when coupled with electrospray ionization. Use of a polymer-based amino analytical column resolved the target compounds from the bulk solvent and provided limited separation among the target compounds. The target analytes were quantified using their [M+NH(4)](+) ions. Sample pretreatment was greatly simplified in comparison with the more commonly used gas chromatographic methods. It involved extraction of aerosol filters in methanol, evaporation of the solvent, and reconstitution with 5 mM ammonium acetate in water prior to the LC-MS analysis. The analyte recoveries were measured at the levels of 100, 500 and 1000 microg/L to be in the range of 78-102%, 94-112%, and 92-110%, respectively. The detection limits were lower than 10 pmol/injection for the tested target compounds except for xylose. Xylose had a detection limit of 95 pmol/injection. The method was applied to analyze 30 atmospheric aerosol samples to demonstrate its feasibility. The LC-MS method made possible the detection of trisaccharides as aerosol constituents for the first time.     

Thermotropic liquid–crystalline properties of 4,4′-dialkoxy-3,3′-diaminobiphenyl compounds and their precursors

A series of 4,4?-dialkoxy-3,3?-diaminobiphenyl compounds were synthesised by three-step procedure that involves alkylation, nitration and reduction reactions. Their chemical structures were characterised by FTIR, ¹H and ¹³C spectroscopy and elemental analysis. Their thermotropic liquid–crystalline (LC) properties were examined by a number of experimental techniques including differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), polarising optical microscopy (POM) and variable temperature X-ray diffraction (VT-XRD). The 4,4?-dialkoxy-3,3?-dinitrobipheyl compounds, precursors to the diamine compounds, were also examined for their thermotropic LC properties. POM studies of focal conic textures and VT-XRD of the 3,3?-diaminobiphenyl derivatives having flexible alkyl chains (C₆–C₁₂) exhibited the smectic A (SmA) phase independent of the length of alkyl chains. Similarly, the 3,3?-dinitrobiphenyl derivatives containing alkyl chains C₇, and C₉–C₁₁ exhibit the SmA phase, those containing C₈ formed the smectic C (SmC) phase and C₁₂ formed both the SmA and smectic B (SmB) phases, respectively. The 3,3?-diaminobiphenyl derivatives had excellent thermal stability in the temperature range of 237–329°C, while those of 3,3?-dinitrobiphenyl derivatives were in the temperature range of 270–321°C. The 3,3?-diaminobiphenyl derivatives emitted UV light both in chloroform and acetonitrile.     

Preparative isolation of procyanidins from grape seed extracts by high-speed counter-current chromatography

High-speed counter-current chromatography (HSCCC) has been applied to the separation of grape seed procyanidins. The isolation of dimeric to tetrameric procyanidins is achieved after removing the polymeric compounds by solvent precipitation. An additional clean-up by solid-phase extraction on polyamide improved the purities of the isolated compounds. The solvent systems ethyl acetate/2-propanol/water (40:1:40, v/v/v), ethyl acetate/2-propanol/water (20:1:20, v/v/v), and ethyl acetate/1-butanol/water (14:1:15, v/v/v) were successfully used for the fractionation. The combination of HPLC-MS, diode array detection, and NMR analysis, as well as phloroglucinolysis, confirmed the structures of the isolated compounds: B1 [EC-(4beta-->8)-C], B2 [EC-(4beta-->8)-EC], B3 [C-(4alpha-->8)-C], B4 [C-(4alpha-->8)-EC], B5 [EC-4beta-->6-EC], B7 [EC-(4beta-->8)-C], [ECG-(4beta-->8)-C], trimeric procyanidin C1 [EC-4beta-->8-EC-4beta-->8-EC], and the tetrameric procyanidin cinnamtannin A2 (where C: catechin, EC: epicatechin and ECG: epicatechin-3-O-gallate).     

Phase transition studies in (p-n-phenylbenzylidene)-p-alkoxy anilines

The variation in density with temperature in seven compounds of p-n-(phenyl benzylidene)-p-alkoxy anilines, PBnOA homologous series has been carried out. The compounds with the alkoxy chain number, n = 1, 3–8, exhibit monovariant nematic phase N (n = 1 and 3), bi-variant NB (n = 4–6) and tri-variant NAB (n = 7 and 8) phases. The density and thermal expansion coefficient results reveal that the phase transitions present viz, isotropic to nematic, nematic to SmA, nematic to SmB, nematic to solid crystal and SmA to SmB in these compounds show first-order nature as expected. Further, these results reveal that all the parameters show characteristic change in the vicinity of the phase transformation. The results are discussed in light of the body of the data available.     

Linkage effects of chromium(III) acetylacetonato units on chiral induction of liquid crystal phases

The linkage effects of polynuclear metal complexes on chiral induction have been studied by application of the chiral oligomers of acetylacetonato chromium(III) units as a dopant, inducing chiral nematic phases. The compounds were prepared by reacting [Cr(acac)(3)] (acac = acetylacetonato) and 1,1,2,2-tetraacetylethane (taetH(2)) in solid phase at 160 degrees C. Binuclear diastereomers were separated on a silica gel column, followed by chromatographic resolution on a chiral column packed with an ion-exchange adduct of Delta-[Ru(phen)(3)](2+) (phen = 1,10-phenanthroline) and synthetic hectorite. An enantiomeric pair (DeltaDelta- and LambdaLambda-[Cr(acac)(2)(taet)Cr-(acac)(2)]) and a meso species (DeltaLambda-[Cr(acac)(2)(taet)Cr(acac)(2)]) were identified. The binuclear enantiomers were doped into a room-temperature nematic liquid crystal, N-methoxybenzylidene-4-n-butylaniline. Helical twisting power (beta(M)) was found to be +97.9 and -88.9 microm(-1) for LambdaLambda- and DeltaDelta-[Cr(acac)(2)(taet)Cr(acac)(2)], respectively. The values were compared with beta(M) for the monomeric enantiomers (+99.5 and -91.0 microm(-1) for Lambda- and Delta-[Cr(acac)(3)], respectively). The results are interpreted on the basis of the surface chirality model. DeltaDelta-[Cr(acac)(2)(taet)Cr(acac)(2)] was found to photoisomerize both in a hexane solution and in a liquid crystal phase of ZLI-1132. The quantum yield of photoisomerization in a liquid crystal phase was lowered to ca. 30% of that in a hexane solution.     

Molecular design of liquid crystalline poly(ester-amide)s with perfluoroalkyl spacers

We have introduced a series of perfluoroalkyl dicarboxylic acids with different lengths of fluorinated aliphatic segments into the 2,6-acetoxynaphthoic acid (ANA) and acetoxy acetanilide (AAA) systems; and their effects on the evolution of liquid crystal texture and liquid crystallinity have been investigated. The perfluoroalkyl dicarboxylic acids are tetrafluorosuccinic acid (TFSA, n=2), hexafluoroglutaric acid (HFGA, n=3), perfluorosuberic acid (PFSUA, n=6) and perfluorosebacic acid (PFSEA, n=8). Computational results based on the 'RIS' Metropolis Monte Carlo method indicate that the ANA/AAA/perfluoroalkyl system may form thermotropic liquid crystalline polymers (LCPs) because the calculated persistence ratios are greater than 6.42. Computational results also predict that the systems containing even-numbered perfluoroalkyl acids have greater persistence length and molar stiffness than that containing odd-numbered acids. Experiments were carried out using the in situ thin film polymerization technique under a polarizing optical microscope. We observed that systems containing short aliphatic units (n=2, 3) tend to remain in the LC phase, while systems containing a long aliphatic spacer (n=8) tend to crystallize during the late stage of the polycondensation reaction. The liquid crystal domain formed in the early stage has a disclination strength S of +1. Ternary phase diagrams were plotted to show the relationship among monomer structure, composition, anisotropic and crystalline phases. FTIR results confirm the formation of LCPs.     

Conductive liquid crystalline compounds having a piperazine structure

New conductive thermotropic liquid crystalline materials having a piperazine ring in the central core: 1-[4-(9-decenyloxy)phenyl]-4-alkylpiperazines ( 6 ) were synthesized. The mesomorphic behaviours of these compounds and their conductivity in the liquid crystal phase were measured. The principal features of these compounds are to exhibit a smectic B phase around room temperature (for example 6 : Cr 50 SmB 81 I, °C) and to exhibit a large dark current (6d: 430 μA cm^-2, applied voltage 20 V, at 70°C) in the smectic B phase.     

Induction and structural control of chiral nematic phases by the use of photoresponsive tris(beta-diketonato) Co(III) and Ru(III) complexes

Two kinds of tris(beta-diketonato) metal(III) complexes denoted as [M(acac)2(LC12)] and [M(acac)2(Lazo)] (M=Ru(III) and Co(III); acac=acetylacetonato; LC12=1,3-didodecyloxyphenyl-1,3-propanedionato; Lazo=3-[4'-(4'-(butoxy)phenylazo)phenyl]-pentane-2,4-dionato) were synthesized and optically resolved into Delta, Lambda isomers. Here, LC12 and Lazo were designed to be elongated perpendicular to and in parallel with the molecular C 2 axis, respectively. The metal complexes were doped into three kinds of nematic liquid crystals (MBBA, EBBA, and ZLI-1132). Both dopants induced chiral nematic phases with relatively high helical twisting powers. With a purpose to clarify the mechanisms of helical induction, order parameters (S) were determined by means of polarized UV-vis measurements on nematic samples doped with racemic Co(III) complexes. As a result, the long axes of the elongated ligands in both [Co(acac)2(LC 12)] and [Co(acac)2(trans-Lazo)] were found to align in the direction of the director vector with S=0.50+/-0.05 and 0.60+/-0.05, respectively. Based on the results, the photoresponsive behavior of Delta- or Lambda-[Ru(acac)2(Lazo)] was interpreted in terms of the variation of S accompanied with the cis-trans isomerization of the azobenzene moiety in Lazo.     

The influence of structural changes of the N‐substituent on liquid crystalline behaviour of ester imides

Several new ester imide derivatives with different N‐substituents in the imide ring were synthesized and their mesogenic properties investigated by thermal analysis, optical microscopy and X‐ray diffraction. All the esters of N‐4‐[(4′‐decyloxybiphenyl‐4‐yl)oxycarbonyl]phthalimideacetic acid and aliphatic alcohols exhibited monolayer SmA and SmC phases. In addition, for the ethyl and propyl esters a monotropic hexatic (F or I) phase was observed. The introduction of additional substituents at the carbon atom in the methylenemethoxycarbonyl group (in the vicinity of the nitrogen atom) substantially influenced liquid crystalline properties: the compounds with a flexible chain exhibited monotropic SmA–SmB dimorphism, but liquid crystalline properties vanished for the substituent containing the more rigid phenyl ring.