Bildung von enantiomerenreinen Flüssigkristallen aus axial‐chiralen Biphenylen

Solladié, Guy; Hugelé, Philippe; Bartsch, Richard; Skoulios, A.

doi:10.1002/ange.19961081329

Cited by 8 publications

(2 citation statements)

References 14 publications

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“…So far, only a few examples of optically active compounds with planar or axial chirality exhibiting LC behaviour have been reported. These include cyclohexylideneethanone derivatives [6], compounds containing a chiral biphenyl core [7], allene derivatives [8], and liquid crystals derived from butadiene(tricarbonyl)iron complexes [9]. Also the first 1,3-unsymmetrically disubstituted optically active LC ferrocene derivative was recently reported [10] 1 ).…”

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confidence: 99%

Thermotropic Liquid Crystals from Planar Chiral Compounds: [2.2]Paracyclophane as a Mesogen Core

Rozenberg

Popova

Hopf

2002

HCA

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New thermotropic mesomorphic compounds containing a [2.2]paracyclophane (PC) unit were synthesized and investigated (Scheme). Carboxylic acids were selected as the starting PC building blocks. The influence of structural features on the stability of the mesomorphic phases was studied (Figs. 1 and 2): for this purpose, the structures of the PC-carboxylate unit and the organic fragment of the aryl-ester moiety were varied systematically. Esters derived from PC-monocarboxylic acid did not exhibit liquid-crystalline (LC) properties, while diaryl PC-dicarboxylates favored mesomorphism. Dicarboxylate substituents arranged in the paraposition provided LC phases in a broad temperature range and considerably increased the mesomorphic interval in comparison with that of the structurally related pseudo-para PC derivatives.Introduction. ± Unique physical properties, providing wide application in electrooptic devices and particularly the recent discovery of new mesophases, such as antiferroelectric, ferrielectric, and twist-grain boundary phases, have put chiral liquidcrystalline (LC) materials in the centre of liquid-crystal research [1] [2]. Historically, up to now, most chiral LC compounds contain molecules incorporating a centre of chirality. More recently, compounds with planar and axial chirality are beginning to attract the growing interest of researchers dealing with LC materials. The unique geometry of this type of compounds provides a rigid interaction between the origin of the symmetry-breaking chirality and the mesogenic unit, thus resulting in a definite fixation of the source of chirality in a LC matrix.In principle, planar chirality could drastically change the physical properties of the resultant LC material: 1) In terms of molecular structure, a rigid steric coupling between the transverse dipole, chiral centre, and the mesogen rod should maximize the local ferroelectric polarization [3], allowing consideration of the above compounds as possible chiral dopants for ferroelectric compositions, which are able to confer a high value of spontaneous polarization (P s ) to the achiral host [4]. 2) Electro-optical effects exhibited by LC materials such as electroclinic effects or nonlinear optical (NLO) properties are expected to be larger for compounds with rigid interaction between the chiral and optical portions of the molecule [5].However, the bulkiness of the structural units necessary to realize an axis or a plane of chirality significantly disturbs the desired rigid rod-like shape of the molecule, thus creating a serious obstacle to achieving stable mesomorphic properties. So far, only a

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confidence: 99%

Thermotropic Liquid Crystals from Planar Chiral Compounds: [2.2]Paracyclophane as a Mesogen Core

Rozenberg

Popova

Hopf

2002

HCA

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“…[4][5][6] Thermotropic chiral liquid crystals can be made from synthesized molecules. A few out of many examples are chiral biphenyls, 7 bis-(binaphtylenedioxy)silane, 5 ester derivatives of hydroxypropylcellulose, 8 P6-M, 9 or copolymers consisting of γ-benzyl glutamate and γ-alkyl glutamate. 10 But also natural chiral mesogens can be found, e.g., DNA, fd virus, and cellulose nanocrystals (CNC).…”

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confidence: 99%

Isotropic-nematic transition and cholesteric phases of helical Yukawa rods

Kuhnhold

Schilling

2016

The Journal of Chemical Physics

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We present a Monte Carlo simulation study of helical Yukawa rods as a model for chiral liquid crystal mesogens. To simulate the cholesteric phase, we introduce a new simulation method that uses soft walls and self-determined boundary conditions. We observe that the isotropic-nematic phase transition is shifted to lower volume fractions with decreasing salt concentration as well as with increasing internal pitch of the rods. For particular sets of interaction parameters, the sense of the cholesteric pitch inverts, i.e., depending on concentration, mesogens of a given handedness can produce cholesteric phases of both chiral senses. Published by AIP Publishing. [http://dx

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Rhodium(I)‐Catalyzed Regiospecific Dimerization of Aromatic Acids: Two Direct CH Bond Activations in Water

et al. 2015

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2,2'-Diaryl acids are key building blocks for some of the most important and high-performance polymers such as polyesters and polyamides (imides), as well as structural motifs of MOFs (metal-organic frameworks) and biological compounds.I nt his study,adirect, regiospecific and practical dimerization of simple aromatic acids to generate 2,2'-diaryl acids has been discovered, whichp roceeds through two rhodium-catalyzed C À Ha ctivations in water.T his reaction can be easily scaled up to gram level by using only 0.4-0.6 mol %o ft he rhodium catalyst. As ap roof-of-concept, the natural product ellagic acid was synthesized in two steps by this method.

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Bildung von enantiomerenreinen Flüssigkristallen aus axial‐chiralen Biphenylen

Cited by 8 publications

References 14 publications

Thermotropic Liquid Crystals from Planar Chiral Compounds: [2.2]Paracyclophane as a Mesogen Core

Thermotropic Liquid Crystals from Planar Chiral Compounds: [2.2]Paracyclophane as a Mesogen Core

Isotropic-nematic transition and cholesteric phases of helical Yukawa rods

Rhodium(I)‐Catalyzed Regiospecific Dimerization of Aromatic Acids: Two Direct CH Bond Activations in Water

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