- Synthesis of aromatic liquid crystals with asymmetric diester based on rod-like multi-ring system by two-step esterification method
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A novel method of two-step esterifications was developed to synthesize compounds with asymmetric double ester groups. By using this method, six rod-like double ester compounds were prepared with p-hydroxy benzaldehyde, p-hydroxy benzoic acid bicyclohexyl carboxylic acid, cyclohexyl benzoic acid and biphenyl carboxylic acid substituted by n-propyl and n-pentyl as main reactants. The structures and properties of target compounds were confirmed by IR, MS, 1H NMR, elemental analysis, differential scanning calorimetry (DSC) and hot stage polarizing optical microscope (HS-POM). Typical yields of the target molecules were more than 70%. All the molecules have mesophases with the textures of nematic type, indicating a rod-like molecule with a longer rigid skeleton can keep its mesophases. There was no clearing point observed for any of the derivatives before they decomposed so that the temperature ranges of the mesophases could not be determined. The energy differences between frontier molecular orbitals (HOMO-LUMO) (Eg) of the compounds were calculated by cyclic voltammetry (CV). The terminal ring system has an obvious influence on the energy levels and the energy gaps (Eg).
- Zheng, Min-Yan,Wei, Yong-Sheng,Geng, Wei,Gu, Yuan-Zi
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- Synthesis of multiring azo-benzoic acid liquid crystalline molecules and their special photosensitive property
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10 new rod-like azo benzoic acid liquid crystals belonged to three series have been prepared, in which trans-cyclohexyl benzene, biphenyl or bi-trans-cyclohexyl carboxylic acid mesogenic cores with ethyl, n-propyl, n-butyl or n-pentyl substituents were connected with azo benzoic acid. Meantime, a simple method was developed in synthesizing compounds bearing both ester and carboxyl groups in one-step reaction. All these compounds have been characterized on the basis of their spectral data, differential scanning calorimeter (DSC) and hot stage polarizing optical microscope (HS-POM). All these compounds have higher thermo-stability. 8 of these compounds have liquid crystalline properties. Their temperature ranges of mesophase have not been obtained, resulting from all the compounds decomposed before their clearing points. Although these compounds are photosensitive in solution under illumination of UV light (365nm), they can't do trans-cis isomerization in their mesophses, indicating the super stabilities of the trans isomer in mesophase.
- Zheng, Min-Yan,Wei, Yong-Sheng,Geng, Wei,Guo, Nai-Ni,Zhang, Ping
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- Multirings aromatic aldehyde liquid crystal with azo linkage and their photosensitivity in mesophase
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Ten new rod-like aromatic aldehyde liquid crystalline molecules with azo linkage were synthesized, in which bi(trans-cyclohexyl), cyclohexyl phenyl, and biphenyl carboxylic acid mesogenic cores with terminal ethyl, n-propyl, n-butyl, and n-pentyl substituents were esterified with azo benzoic aldehyde. These molecules were designed in an attempt to construct a series of new azo liquid crystalline molecules to investigate the influence of ultraviolet (UV) light on their mesophase. All compounds have been characterized on the basis of their spectral data, differential scanning calorimeter (DSC), and hot stage polarizing optical microscope (HS-POM). All these compounds exhibited liquid crystalline phase that belonged to nematic and photosensitive properties. Their temperature ranges of mesophase are from 101°C to 150°C. Under irradiated 365 nm UV light, they showed photosensitivity in the solvent of methanol. Observed under HS-POM, the UV light also did change the textures of these compounds. The result showed that terminal ethyl is enough for these molecules to exhibit wider temperature range of mesophase, and these new molecules have photosensitivities observed under illumination of UV light not only in solution but also in mesophase due to the change of their structures from trans isomer to cis one.
- Zheng, Min-Yan,Wei, Yong-Sheng,Gu, Yuan-Zi,Wang, Shan
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p. 151 - 164
(2014/07/07)
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- Synthesis of new mesogens of the 3-arylisoxazolone and 3-arylpyrazolone series
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Acylation of ethyl acetoacetate with mesogenic para-substituted benzoyl chlorides, followed by cleavage of ethyl aroylacetoacetates thus obtained under basic conditions, gave the corresponding ethyl 3-aryl-3-oxopropanoates which were brought into condensations with hydroxylamine and hydrazine to obtain mesogenic 3-arylisoxazolones and 3-arylpyrazolones, respectively. Pleiades Publishing, Ltd., 2010.
- Kovganko,Kovganko,Polovkov
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body text
p. 1812 - 1816
(2011/04/17)
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- Synthesis and magnetic properties of some crystalline nitroxide radicals
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The syntheses of different nitroxide radicals are reported. The thermal behaviour of the nitroxide radicals was examined by polarizing microscopy, differential scanning calorimetry as well as X-ray diffraction experiments. Temperature dependent magnetic susceptibility measurements were carried out in order to determine the magnetic properties of these nitroxide radicals. The majority of the radicals presented here show weak antiferromagnetic exchange interactions.
- Griesar,Soto-Bustamante,Haase
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p. 567 - 575
(2007/10/03)
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- SYNTHESIS AND LIQUID CRYSTAL PROPERTIES OF SUBSTITUTED 5-(ARYLCARBONYLOXY)-2-(p-CYANOPHENYL)PYRIMIDINES
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Liquid crystal p-substituted benzoates, biphenylcarboxylates, and benzoyloxybenzoates were obtained on the basis of 5-hydroxy-2-(p-cyanophenyl)pyrimidine.The development of nematogenicity by the esters due to the p-cyanophenyl grouping was noted, and the appearance of the smectic mesophase by the variation of the ring framework of the acid fragment of the molecule was investigated.
- Mikhaleva, M. A.,Igonina, G. A.,Savel'ev, V. A.
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p. 320 - 325
(2007/10/03)
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- A New Class of Chiral Smectic Liquid Crystals: Substituted Biphenylylcyclohexylideneethanones Having an Axial Chirality
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The introduction of chiral cyclohexylideneethanone unit in a potential mesomorphic structure leads to the first family of optically active liquid crystals having an axial chirality.Racemic compounds 2 were synthesized by a Wittig-type coupling between β-keto phosphonates 6 (R1 = n-C5H11) and substituted cyclohexanone 7 (R2 = H, CH3, t-Bu, OCH3, O-n-C5H11, CO2Et, OCOC6H4CN, OCOC6H4Cl).The optically active molecules 12 were prepared by a new route using the asymmetric coupling of a carbanion α to a chiral sulfoxide 9 (R2 = n-C5H11, CH2OEt) and a substituted biphenyl acid chloride (Ar = R'C6H4C6H4 with R' = n-C5H11, CH3O, n-C8H17O, CN) followed by a stereospecific pyrolytic elimination of the sulfoxide moiety.Derivatives containing only one aromatic ring were not mesomorphic in contrast to those having a biphenyl system.
- Solladie, Guy,Zimmermann, Richard
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p. 4062 - 4068
(2007/10/02)
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- 180. Some Novel Nematic Materials Bearing Two Lateral Nitrile Functions
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More than fifty esters of 3-alkyl-6-hydroxy-1,2-benzenedicarbonitrile have been prepared.The new esters exhibit stable nematic phases of high negative dielectric anisotropy.The relationship between the clearing points of the esters and the various ring they incorporate is the same as that normally observed for nematic materials of positive dielectric anisotropy.
- Kelly, Stephen M.,Huynh-Ba, Tuong
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p. 1850 - 1859
(2007/10/02)
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- Ortho Cyano Substituted Negative Dielectric Anisotropic Liquid Crystals
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A homologous series of 2'-cyano-4'-n-alkylbiphenylcarboxylates and 4-n-alkylcyclohexyl-p-benzoates were synthesized by treating 2'-cyano-4'-n-alkyl substituted phenols with 4-n-alkyl substituted biphenyl carboxylic acids and cyclohexyl benzoic acids.The method of synthesis was discussed.All these compounds were nematogenic in character and their phase transition temperatures were examined.A wide range of mesomorphism was observed in almost all the homologous series.IR, NMR, and dielectric property of these compounds were studied studied.The negative dielectric anisotropic property of these liquid crystalline compounds makes them suitable for application in positive GH display devices.
- Hong, X. J.,Ge, M. J.,Zhao, X. M.,Fen, Z. R.,Liu, Z. J.
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