Molecular conformation effects on mesomorphism and twisting ability of chiral cyclohexanones in mesophases

Kutulya, L. A.; Krivoshei, A. I.; Pivnenko, N. S.; Shkolnikova, N. I.

doi:10.1007/s10947-005-0005-x

Cited by 6 publications

(4 citation statements)

References 14 publications

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“…A combination of the above geometric parameters determines intrinsic helical chirality of the examined structures. Analogous structural specificity was observed previously for some other α,β-unsaturated ketones with s-configuration of the enone fragment fixed by six-membered ring [16][17][18][19]. This is especially important for chiral structures which thus acquire intrinsic helical chirality.…”

Section: Iiia-iiiesupporting

confidence: 69%

“…As a result, statistical twisting power of conformationally equilibrium systems should be reduced. Insofar as structurally related chiral compounds with the same character of molecular twist give rise to helical structures with the same sign in liquid crystals [18,19], the above analysis of relations between the twisting power of chiral additives in liquid crystals and geometric parameters of molecules (determined by X-ray analysis of crystals) may be regarded as appropriate.…”

Section: Iiia-iiiementioning

confidence: 99%

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New chiral 3-aryl-7-arylmethylidene-3,3a,4,5,6,7-hexahydroindazoles: Synthesis, structure, and twisting power in nematic liquid crystals

et al. 2010

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3R)-2,6-Bis(arylmethylidene)-3-methylcyclohexanones and 3-(4-X-aryl)-7-(4-X-arylmethylidene)-3,3a,4,5,6,7-hexahydro-2,6-and -2,4-dimethyl-2H-indazoles (X = Cl, HO, AlkO, AlkOCO, MeOC 6 H 4 COO) as potential chiral additives to liquid crystalline systems were synthesized starting from (3R)-3-methylcyclohexanone. Relations between the twisting power and molecular structure of the synthesized compounds are discussed.Modern compositions for imaging devices based on liquid crystalline materials usually contain several components, among which chiral additives are important. Such additives are capable of inducing formation in mesophase of helical supramolecular structures via transformation of nematic (N) and smectic-C (SmC) phases into cholesteric and ferroelectric SmC* [1-4]. Diversity of requirements to chiral components of liquid crystals makes search for new chiral additives an important problem. Biological activity of substituted hexahydroindazoles and their N-methyl and sulfonyl analogs was studied [5][6][7][8], and their chemical properties were also examined.The present study was aimed at synthesizing photostable chiral additives with a strong twisting power on the basis of (3R)-3-methylcyclohexanone (I). A general procedure for the synthesis of 2-substituted hexahydroindazoles is based on reaction of benzylidenecyclohexanones with hydrazine derivatives in the presence of hydrochloric [5,9] or acetic acid [6], as well as in the absence of a catalyst in alcoholic medium [7]. Syntheses under basic conditions are less common [10]; in these cases, alternative products are formed [11][12][13].We found that the reactivity of initial ketones II toward various hydrazine derivatives is considerably lower than the reactivity of 2,6-bis(arylmethylidene) cyclohexanones. Both ketones II and 2,6-bis(arylmethylidene)cyclohexanones readily reacted with hydrazine and methylhydrazine, whereas the former failed to react with phenylhydrazine and thiosemicarbazide. Hexahydroindazoles obtained by the reaction with hydrazine readily undergo oxidation with atmospheric oxygen. Even though N-acylation stabilizes these compounds, their twisting power in liquid crystals strongly weakens. We considered compounds III and IV as target components of liquid crystalline compositions. They were synthesized under conditions of base catalysis using triethylamine (in the synthesis of IIIb) [14] or excess methylhydrazine (IIIa-IIIe) to avoid tarring in acid medium. In the general case, the reaction with methylhydrazine gives two groups of regioisomeric products III and IV (Scheme 1), depending on the double bond (C 2 =C or C 6 =C) involved in the formation of pyrazole fragment; in addition, cis-trans isomerism with respect to the C 3 -C 3a bond is possible; therefore, eight regio-and stereoisomers may be formed.In fact, the 1 H NMR data showed the presence in the reaction mixtures of appreciable amounts of three or four compounds, which were identified by the signal from the methyl group on the cyclohexane ring. In the reaction with ketone IIb we su...

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Section: Iiia-iiiesupporting

confidence: 69%

Section: Iiia-iiiementioning

confidence: 99%

New chiral 3-aryl-7-arylmethylidene-3,3a,4,5,6,7-hexahydroindazoles: Synthesis, structure, and twisting power in nematic liquid crystals

et al. 2010

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“…It was revealed that an important role belongs to the presence in CAd molecules of a highly polarized π electronic system, including that fixed by the saturated cycle of the s cis enone group or its enhydrazone analog >С=С-C=N-N< (see Refs 8,10,12,13,and 15). Nevertheless, the role of various structural features of chiral molecules as factors determining their helical twist ing power in mesophases is studied incompletely.…”

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confidence: 99%

“…According to the existing concepts (see, e.g., Refs 5,8,10,and 11), the most important molecular factors determining the efficiency of formation of the supramo lecular helix in the mesophase upon the introduction of the CAd are the molecular polarizability (its anisotropy and chirality) and the shape of the additive molecules. The theoretical simulation in the framework of the semiempirical AM1 method 18 was performed to elucidate the molecular shape of the CAd of the studied type.…”

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New steroid α,β-unsaturated ketones as chiral components of induced cholesteric liquid crystal systems

et al. 2009

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Molecular structures of regioisomeric 7‐arylidene hexahydroindazoles from ¹H NMR spectra

Pivnenko

Туров

Abakumov

et al. 2009

Magnetic Reson in Chemistry

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The structural characterization of two regioisomeric products of the interaction of 2,6-bis-(4-methoxybenzylidene)-3R-methylcyclohexanone with methyl hydrazine was achieved using (1)H NMR spectral data, including chemical shifts, coupling constants and results of COSY and nuclear overhauser effect (NOE) experiments. Configurations of the new chiral centers in the (3S,3aR,6R,7E)-7-(4-methoxybenzylidene)-3,4,5,7-hexahydro-3-(4-methoxyphenyl)-2,6-dimethyl- and 2,4-dimethyl-2H-indazoles were assigned on the basis of experimental data combined with molecular modeling by the density functional theory (DFT) method. The distinction in the helical twisting power of studied compounds under addition to a nematic liquid crystal is discussed on the basis of peculiarities of the molecular structures.

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Molecular conformation effects on mesomorphism and twisting ability of chiral cyclohexanones in mesophases

Cited by 6 publications

References 14 publications

New chiral 3-aryl-7-arylmethylidene-3,3a,4,5,6,7-hexahydroindazoles: Synthesis, structure, and twisting power in nematic liquid crystals

New chiral 3-aryl-7-arylmethylidene-3,3a,4,5,6,7-hexahydroindazoles: Synthesis, structure, and twisting power in nematic liquid crystals

New steroid α,β-unsaturated ketones as chiral components of induced cholesteric liquid crystal systems

Molecular structures of regioisomeric 7‐arylidene hexahydroindazoles from ¹H NMR spectra

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Molecular conformation effects on mesomorphism and twisting ability of chiral cyclohexanones in mesophases

Cited by 6 publications

References 14 publications

New chiral 3-aryl-7-arylmethylidene-3,3a,4,5,6,7-hexahydroindazoles: Synthesis, structure, and twisting power in nematic liquid crystals

New chiral 3-aryl-7-arylmethylidene-3,3a,4,5,6,7-hexahydroindazoles: Synthesis, structure, and twisting power in nematic liquid crystals

New steroid α,β-unsaturated ketones as chiral components of induced cholesteric liquid crystal systems

Molecular structures of regioisomeric 7‐arylidene hexahydroindazoles from 1H NMR spectra

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Molecular structures of regioisomeric 7‐arylidene hexahydroindazoles from ¹H NMR spectra