| | 3 | Author
| V. Salas-R, G. Eyesa, Soto-G, C. A. Arridob, Guilera0 | Requires cookie* | | | Title
| Synthesis and Characterization of Bis(3-chloro-4-dodecyloxyphenyl) Malondialdehyde Complexes of Cu(II) and Ni(II)  | | | | Abstract
| Bis (3-chloro-4-dodecyloxyphenyl) malondialdehyde copper(II), as well as its nickel(II) homologue have been synthesised. The copper(II) complex shows a narrow (15 °C) nematic phase below its clearing temperature. The nickel(II) complex is polymeric in nature. | | | |
Reference
| Z. Naturforsch. 51b, 1679—1682 (1996); received July 8 1996 | | | |
Published
| 1996 | | | |
Keywords
| Metallomesogens, Liquid Crystals, Copper Complexes, Dialdehydes, Formylation | | | |
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| default:Reihe_B/51/ZNB-1996-51b-1679.pdf | | | | Identifier
| ZNB-1996-51b-1679 | | | | Volume
| 51 | |
| 4 | Author
| C. Aguilera, M. Parra, G. Fuentes | Requires cookie* | | | Title
| Synthesis and Mesomorphic Properties of Polymethylene-a,u;-bis [2-thio- 5-(4',4"n-alcoxybenzoyIoxy)phenyl]-l,3,4-oxadiazole | | | | Abstract
| Three homologous series of polymethylene-a,i<;-bis[2-thio-5(4',4''n-alkoxybenzoyloxy)-phenyl]-l,3,4-oxadiazole (series 5 a, b, c), are reported.The compounds have identical meso-genic units at both ends of a spacer (i.e. they are twins). These twins possess a spacer of 6, 8 and 10 carbon atoms joined directly to the oxadiazole ring through sulphur atoms. The lateral alkylic chains vary between 6 and 10 carbon atoms.The presence of enantiotropic and m onotropic nematic phase is related to the length of the spacer group. The influence of molecular structure on the mesomorphic properties has been studied. Me somorphic properties and phase transitions have been determined using polarizing hot-stage microscopy and differential scanning calorimetry. | | | |
Reference
| Z. Naturforsch. 53b, 367—370 (1998); received May 15 1997 | | | |
Published
| 1998 | | | |
Keywords
| Liquid Crystal, Twin Mesogens, Oxadiazole, M esomorphic Properties | | | |
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| default:Reihe_B/53/ZNB-1998-53b-0367.pdf | | | | Identifier
| ZNB-1998-53b-0367 | | | | Volume
| 53 | |
| 6 | Author
| Andreas Eckert, Bernd Kohne, Klaus Praefcke | Requires cookie* | | | Title
| Flüssigkristalline Kohlenhydratdithioacetale * * Liquid Crystalline Carbohydrate Dithioacetals* | | | | Abstract
| Aus Anlaß der vor 100 Jahren vom Botaniker F. Reinitzer [1] und dem Physiker O. Lehmann [2] begonnenen Flüssigkristallforschung [3] Various S,S-dialkyl acetals of hexanal and numerous aldoses, tripodal in structure, have been synthesized, characterized and investigated by optical microscopy and D. S. C. Most of these geminal dithioacetals show a complicated melting behaviour and are thermotropic liquid crystal-line, exhibiting only one smectic-like phase of identical type. This mesophase is not miscible with the S Ad -Phase of other amphiphilic sugar-based liquid crystals. As shown in a homologues series of D-glucose S.S-dialkylacetal derivatives clearing points are rising as function of growing number n of carbon atoms in their S-alkyl chains. With constant n given a similar trend is observed by varying the length of the polar, hydrophilic sugar units. Regarding stereochemistry the dithioderivatives 5 and 12 of the pentose or hexose series, respectively, with a configuration related to that of D-mannose exhibit relatively the most stable mesophase. However, the most stable mesophase of all investigated sugar dithioderivatives is exhibited by the heptose S.S-dialkylacetal 13. Surprisingly, derivative 10 of L-rhamnose (6-desoxy-L-mannose) — the terminal hydroxyl group in the sugar chain of mannose is missing! -showed to be non-mesomorphic, demonstrating that a terminal hydroxyl group of these sugar derivatives seems to be essential for exhibiting a mesophase. On the other hand, as shown with the dithioderivative 9 of 2-desoxy-D-glucose in comparison to the derivative 8e and 12 of D-glucose or D-mannose, respectively, their clearing points seem to be less, although differently effected if an internal hydroxyl group — for instance here at C-2 — has been stripped off. Melting behaviour as well as thermomesogenic properties of the presented amphiphilic carbo-hydrate liquid crystals in relationship to their molecular structure are discussed in detail. | | | |
Reference
| Z. Naturforsch. 43b, 878—888 (1988); eingegangen am 22. Dezember 1987 | | | |
Published
| 1988 | | | |
Keywords
| Aldoses, Liquid Crystals, Mesophases Sugar SS-Dialkyl Acetals, Tripodal Amphiphiles | | | |
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| default:Reihe_B/43/ZNB-1988-43b-0878.pdf | | | | Identifier
| ZNB-1988-43b-0878 | | | | Volume
| 43 | |
| 7 | Author
| V.Salas Reyes3, C. Aguilerab | Requires cookie* | | | Title
| Synthesis and Characterization of Copper(II) and Nickel(II) Complexes Derived from «-Substituted Malondialdehydes | | | | Abstract
| The synthesis and characterization of two series of novel bis(4'-alkyloxyphenyl)m alondi-aldehydes of copper(II) and nickel(II), (R=C"H2"+1, n = 9, 10, 11, 12) from 2-(4'-hydroxy-phenyl)-3-dimethylamino acrolein is described. | | | |
Reference
| Z. Naturforsch. 50b, 205 (1995); received September 28 1994 | | | |
Published
| 1995 | | | |
Keywords
| M alondialdehyde, Acroleins, Formylation, M etallom esogen, Liquid Crystal | | | |
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| default:Reihe_B/50/ZNB-1995-50b-0205.pdf | | | | Identifier
| ZNB-1995-50b-0205 | | | | Volume
| 50 | |
| 8 | Author
| MagedA. Osman, M. A. Osman | Requires cookie* | | | Title
| Nematic Liquid Crystals with High Positive Dielectric Anisotropy * Nematic Liquid Crystals 1093 *>-®-CH-N-©-CN | | | | Abstract
| Alkylamino-and formyl alkylamino-cyano Schiff's base, biphenyl and phenylbenzoate liquid crystals were synthesized. The mesomorphic behaviour of these compounds is described. The introduction of the formyl group in the higher homologues lead to the disappearance of the mesophase. The alkylamino and formylalkylamino substituents are strong electron donating groups and lead to nematic phases with remarkably high positive dielectric anisotropy. Interest in electrooptical displays based on the twisted nematic effect [1] has lead to a growing demand for nematic liquid crystals with positive dielectric anisotropy. Non-polar or almost non-polar nematic compounds of the type 1 were found to possess a very small positive dielectric anisotropy (As = 0.05-0.5) [5-7], X =-CH= N-|21 , -C00-131,—N=N— |4| 1 Nematic phases of the Schiff's base and phenyl-benzoate type with larger A a were synthesized by A. Boiler [8, 9] through replacement of one of the alkyl groups by the cyano group which possess a larger dipole moment (—4 D). The remaining alkyl group on the other end of the molecule, which has a dipole moment of -f-0.3 D, was not changed. Recently, G. Gray [10] and R. Eidenschink [11] prepared analogous nematic phases of the biphenyl and phenyl cyclohexane types. All these compounds have A e values from 8 to 20 [12-14] which allow an operating voltage of 3 volts for a twisted nematic display. Since the threshold voltage and, correspond-ingly, the operating voltage is proportional to \J11A e, it is clear that new nematic liquid crystals with larger dielectric anisotropics are required if the operating voltage is to be substantially reduced. This can be achieved by replacing the remaining alkyl group with an electron donating substituent having a stronger dipole moment along the molecu-lar axis. The first attempt along this line was made by introducing the dimethylamino group (-(-1.6 D) * Reprint requests to Dr. M. A. Osman. 0340-5087/79/0800-1092/$ 01.00/0 at the other end of the benzyliden-aminobenzo-nitrile molecule, but this gave an isotropic com-pound melting at 183 °C [15]. The disappearance of the liquid crystalline properties is probably due to the high melting point of this compound and to the bulkiness of the dimethylamino group which lowers its clearing point. The aim of this work is to introduce the less bulky monoalkylamino group in molecules of type 1 and to study the effect of this substitution on their mesomorphic behaviour and on the magni-tude of the dielectric anisotropy. Results and Discussion N-(4-Methylaminobenzylidene)-4'-aminobenzo-nitrile (2) was prepared by condensing 4-methyl-aminobenzaldehyde with 4-aminobenzonitrile in bulk [16]. CH3HN-^)-cho+H2N-<Q>-CN-^CH3HN-Q>-CH-N^Q>-CN z The aldehyde was prepared by the Vilsmeier re-action [17]. 2"c> ~HjC :N CN H0 ~ H 3 CHN <> CHO Compound 2 melted at 163.1 °C and showed a monotropic nematic phase clearing at 138.0 °C. This confirmed that the disappearance of the meso-phase in the dimethylamino derivative was caused by the bulkiness of this group. However, the melting point of compound 2 is too high for practical applications and for conveniently measuring the dielectric anisotropy. The higher homologues of alkylaminobenzaldehyde and their Schiff's bases were therefore prepared in an attempt to lower the melting point. It seemed also of interest to | | | |
Reference
| Z. Naturforsch. 34b, 1092—1095 (1979); received March 23 1979 | | | |
Published
| 1979 | | | |
Keywords
| Liquid Crystals, Nematic Phases, High Positive Dielectric Anisotropy, Alkylamino-cyano-biphenyls, Alkylamino-cyano-phenylbenzoates | | | |
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| default:Reihe_B/34/ZNB-1979-34b-1092.pdf | | | | Identifier
| ZNB-1979-34b-1092 | | | | Volume
| 34 | |
| 9 | Author
| Jan Böm, G. Erd, Heppke, A. Ndreas Ranft | Requires cookie* | | | Title
| Synthese und ferroelektrische Eigenschaften chiraler Ester von 2,5-Diphenylpyrimidinen mit a-Fluorcarbonsäuren Synthesis and Ferroelectric Properties of 2,5-Diphenylpyrimidines with Different a-Fluorocarboxylic Acids | | | | Abstract
| Chiral esters of 2-[4-/?-hexylphenyl]-5-[4-hydroxyphenyl]pyrimidine and 2-[4-w-hexyloxy-phenyl]-5-[4-hydroxyphenyl]pyrimidine with four different a-fluorocarboxylic acids have been synthesized. The spontaneous polarization and the tilt angles in the smectic C* phase were m easured as a function of tem perature. All compounds exhibit wide range smectic C* phases, the highest values of the spontaneous polarization being about 400 nC/cm: . Additionally the spon taneous polarization in a higher ordered smectic phase was determ ined, the values ranging up to about 600 nC/cm2. The spontaneous polarization/tilt angle ratio strongly increases with decreasing tem perature. | | | |
Reference
| Z. Naturforsch. 44b, 1127—1131 (1989); eingegangen am 6. März 1989 | | | |
Published
| 1989 | | | |
Keywords
| Liquid Crystals, Smectic Liquid Crystals, Ferroelectric Properties, Chiral cc-Fluorocarboxylic Acid E sters, 2, 5-Diphenylpyrim idines | | | |
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| default:Reihe_B/44/ZNB-1989-44b-1127.pdf | | | | Identifier
| ZNB-1989-44b-1127 | | | | Volume
| 44 | |
| 10 | Author
| Bernd Kohne, Klaus Praefcke, Werner Stephan, Peter Nürnberg | Requires cookie* | | | Title
| Discotische Flüssigkristalle: Beziehung zwischen Molekülstruktur und discogenen Eigenschaften scheibenförmiger Verbindungen, /iic/rf-flüssigkristalline Ester des //ryo-Inosits und des Mytilits [ 1 , 2 ] Discotic Liquid Crystals: Relation between Molecular Structure and Discogenic Properties of Disc-shaped Compounds, Non-liquid Crystalline Esters of m yo -Inositol and Mytilitol [1,2] | | | |
Reference
| Z. Naturforsch. 40b, 981 (1985); eingegangen am 25. März 1985 | | | |
Published
| 1985 | | | |
Keywords
| Cyclitols, D erivatives o f Natural Products, C yclohexane D erivatives, Liquid Crystals, Cores o f D iscogenic Com pounds | | | |
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| default:Reihe_B/40/ZNB-1985-40b-0981.pdf | | | | Identifier
| ZNB-1985-40b-0981 | | | | Volume
| 40 | |
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