Effect of the nature of chiral fragment on mesomorphic properties of triphenylene ethers

A number of new 2,3,6,7,10,11-hexakis(heptyloxy)triphenylenes possessing a chiral substituent in position 1 of the triphenylene ring system and characterized by predictable mesomorphism were synthesized. The effect of the nature of the chiral fragment (dehydrocholic, lipoic, and d-tartaric acid residues) on the mesomorphic properties of triphenlylene ethers was studied. N-[2,3,6,7,10,11-hexakis(heptylozy)triphenylen-1-yl]amides derived from the above acids, unlike initial monomesomorphic amine, exhibit enantiotropic columnar polymorphism and give rise to helical columnar structure at reduced temperature. The newly synthesized amides are characterized by lower thermal stability and broader temperature range of the mesophase. Introduction of two chiral dehydrocholic acid fragments into the triphenylene core favors columnar (including chiral) mesomorphism.     

Epitaxygens: mesomorphic properties of triptycene derivatives

The structure of mesophases derived from a triptycene subunit substituted with five paraffinic chains has been determined by X-ray diffraction at small angles. They all show a smectic ordering. This is the first example of a smectogen whose rigid core belongs to the D_3h symmetry. A hexagonal order has been observed in the X-ray diffraction patterns; it has been associated with a p31m packing of the rigid cores within the layers. The intralamellar cell parameter is in agreement with the molecular dimensions determined from CPK models. The calculated molecular length is in accordance with the experimental interlamellar distance. The difference in mesomorphic behaviour between the five and six chain derivatives is discussed.     

Influence of branched chains on the mesomorphic properties of symmetrical and unsymmetrical triphenylene discotic liquid crystals

A series of novel symmetrical and unsymmetrical triphenylene‐based discotic liquid crystalline materials with one or six branched peripheral alkoxy chains have been prepared. These materials have been compared with analogous known symmetrical and unsymmetrical compounds to reveal a balance between steric and space‐filling effects of the peripheral branched chains, which significantly affects intermolecular forces of attraction and packing, and hence affects melting and isotropisation temperatures of the liquid crystalline materials. The desired result of reduction of melting points and enhancement of isotropisation temperatures has been accomplished by use of branched alkoxy chains in both symmetrical and unsymmetrical materials.     

Synthesis of pyran derivatives with mesomorphic properties

N-(4-Arylidene)-4-(3,6-dihydro-4-methyl-2H-pyran-3-yloxy)anilines and N-(4-arylidene)-4-[(5,6-dihydro-2H-pyran-4-yl)methoxy]anilines that have the properties of smectic and nematic liquid crystals were synthesized. The effect of the pyran ring and the length of the aliphatic radical on the type and thermal stability of the meso phase was elucidated.Fortieth Anniversary of the October Revolution Bashkir State University, Ufa 450074. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 897–899, July, 1991.     

Synthesis and mesomorphic properties of four ring,rod-like fluorene derivatives – the influence of the lateral substitution on mesomorphic properties of 2,7-bis(4-alkylphenyl)-fluorenes

ABSTRACT

This work presents new rod-like compounds being fluorene derivatives linked with other parts of the core at 2 and 7 positions – its synthesis and properties. The fluorene moiety is located in the central position of the four rings molecular core. The chain system in most cases was symmetrical and limited to pentyl or hexyl chains. To study the influence of the lateral substituents on mesomorphic properties two types of substituents have been incorporated, centrally located various short alkyl groups at fluorene’s 9,9 positions and outer core fluorosubstitutions located at side phenyl rings. All synthesised compounds exhibit liquid crystalline properties, where for laterally non-substituted and fluorosubstituted derivatives the dominant phases are smectics, while the nematics phases (nematic and chiral nematic – observed mostly on cooling cycle) occurs for compounds having alkyl substituents at 9,9 positions of fluorene. The synthetic methodology and mesomorphic properties of title compounds will be presented in detail as well as photophysical properties such as UV-visible absorption spectra and fluorescence spectra.     

Preparation,spectral and thermal properties of new Isoflavone derivatives: mesomorphic properties and DFT studies

The four new homologous series of symmetric Isoflavon dimers were synthesised using varied alkyl/aryl diamines in linear sense. The chemical structures of the molecules were characterised by IR, NMR and CHNS analysis. Further, Liquid crystalline properties were verified using the combination of differential scanning calorimetry (DSC) and polarised optical microscope (POM). The molecular systems studied here reveal that LC property depends on the length of the middle connecting diamine spacer along with terminal alkyl spacer. The lower members favour to exhibit smectic A phase, whereas higher members exhibit nematic mesophase. The nature of LC property behaviours is supported by molecular geometries studied by DFT calculations.     

The synthesis and properties of some mesomorphic cyclohexene derivatives

This paper describes the synthesis and mesomorphic properties of some new liquid crystalline cyclohexene derivatives.     

Syntheses and mesomorphic properties of novel triphenylene liquid crystals with 15-crown-5 unit as side-chain

Two novel triphenylene liquid crystals with 15-crown-5 unit as side-chain 4a and 4b were designed and synthesised by simple procedures in ideal yields. Their structures were confirmed by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (¹H NMR), electrospray ionization mass spectrometry (ESI-MS) and elemental analysis. Their liquid-crystalline behaviours before and after complexation with metallic salts were studied by differential scanning calorimetry, polarising optical microscopy and X-ray diffraction. Neat compounds 4a and 4b show mesophase with triphenylene column, while complexes of 4a and 4b with metallic salts exhibit no mesophase but higher melting point.     

Synthesis and investigation of the mesomorphic properties of pyran derivatives

4-[(5,6-Dihydro-2H-pyran-4-yl)methoxy]benzylidene-4-alkoxyanilines, which have the properties of smectic liquid crystals, were synthesized. The effect of the pyran ring in the benzylidene component and the length of the aliphatic radical in the aniline component on the type and thermal stability of the meso phase was ascertained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 327–328, March, 1992.     

Synthesis and properties of alkylthiomethylated urea derivatives

Novel N,N′-bis[(alkylsulfanyl)methyl]ureas were prepared by three-component condensation of urea with formaldehyde and thiol in a NaOH solution, and alkylthiomethylated polymethyleneureas were prepared by the condensation of the same reactants in the presence of glacial acetic acid and without it. Polymethyleneureas efficiently sorb silver(I) from nitric acid solutions and palladium(II) from hydrochloric acid solutions. Alcoholsoluble N,N′-bis[(alkylsulfanyl)methyl]ureas inhibit carbon dioxide corrosion of St.3 steel.     

Synthesis and mesomorphic properties of benzoxazole derivatives with lateral multifluoro substituents

Fluorinated aromatics is generally chosen as mesogenic cores to design novel liquid crystal compounds. Here, a series of benzoxazole derivatives with laterally multifluorinated biphenyl units, 2-(3′,3-difluoro ?4′-alkoxy-1,1′-biphenyl-4-yl)-benzoxazole derivatives (coded as nPF(3)PF(3)Bx), are synthesized and characterized, where methyl and nitro moieties are selected as terminal groups to investigate the effects of different polar substituents on the liquid crystal properties. The compounds nPF(3)PF(3)Bx show enantiotropic mesophases with mesophase ranges of 0–40°C and 0–63°C on heating and cooling for hydrogen-terminated derivatives (nPF(3)PF(3)BH), 43–93°C and 54–123°C for methyl-terminated ones (nPF(3)PF(3)BM), 60–108°C and 74–152°C for nitro terminated ones (nPF(3)PF(3)BN), respectively. They exhibit photoluminescence emission peaks at 390–392 nm and UV–vis absorption bands with maxima at 327–330 nm, respectively. The results reveal that lateral multifluoro substituents lead to a decrease in melting/clearing points, while electron-withdrawing terminal nitro moiety results in increases in both melting point and mesophase range.     

Synthesis and mesomorphic properties of 2,6-disubstituted derivatives of quinoline: amides and esters

Thesyntheses of N-4-n-alkoxyphenyl-6-n-decyloxyquinoline-2-carboxamide(alkoxy=CnH2n+1O, n=4-10) and 4-n-alkoxyphenyl-6-n-decyloxyquinoline-2-carboxylate (n=4,6,8) are described along with the measurement of their physical properties using DSC and optical methods. The amides all show an enantiotropic smectic A phase while the esters show monotropic mesophases. A study of the structure/mesomorphic activity relationship is also described.     

LC diketones: synthesis,transformations and mesomorphic properties

The synthesis and chemical transformations of various diketones into liquid crystalline compounds are discussed. The diketones were prepared by the interaction of cyclohexene with acid chlorides and benzene in the presence of aluminium chloride (Nenitzescu method) or by Friedel Crafts reaction of trans-4-alkanoyl-1-phenylcyclohexanes or trans-2-alkyl-5-phenylcyclohexanones with acid chlorides, or by the condensation of corresponding Mannich salts with 2-substituted acetoacetates or acetylacetone.     

LC diketones: synthesis, transformations and mesomorphic properties

The synthesis and chemical transformations of various diketones into liquid crystalline compounds are discussed. The diketones were prepared by the interaction of cyclohexene with acid chlorides and benzene in the presence of aluminium chloride (Nenitzescu method) or by Friedel Crafts reaction of trans-4-alkanoyl-1-phenylcyclohexanes or trans-2-alkyl-5-phenylcyclohexanones with acid chlorides, or by the condensation of corresponding Mannich salts with 2-substituted acetoacetates or acetylacetone.     

Synthesis and mesomorphic properties of some cyclohex-2-en-1-one derivatives

Mesomorphic properties of cyclohex-2-en-1-ones belonging to 14 different chemical structural types are compared and discussed. They were prepared by condensation of Mannich salts with 2-substituted acetoacetates or benzyl methyl ketones or acetylacetone in the presence of potassium hydroxide.     

Amide linkage in novel three-ring bent-core molecular assemblies: polar mesophases and importance of H-bonding

Here, we report the first examples of achiral unsymmetrical three-ring bent-shaped liquid crystals comprising amide and imine linkages with transverse substituents of methyl and chloro moieties on the central phenyl ring in the core, exhibiting polar banana phases. The extensive intra and inter molecular H-bonding induced novel banana mesomorphic phases. One-dimensional stacking in the mesomorphic phase as well as ferroelectric polar order promoted by intermolecular H-bonding of amide linkage is demonstrated. The compounds exhibit multifunctional properties viz., the enantiotropic liquid crystalline (LC) phase at ambient temperatures, electro-optical response, spontaneous polarisation, emission characteristics with large Stokes shift, and even charge distribution with large voltage holding ratio (VHR) values. The smectic type phase was confirmed by XRD studies and polar order was established by switching current and dielectric investigations. DFT studies revealed the importance of their suitability for display applications.     

Heterocyclic columnar pyrimidines: synthesis, characterization and mesomorphic properties

The synthesis, characterization, and mesomorphic properties of two series of heterocyclic compounds derived from a pyrimidine core are reported. These series, 1a and 1b, are substituted with a variety of functional groups (X=NHSO₂CF₃, F, Cl, Br, I, OCH₃, CH₃, C₂H₅) at the C^3' (meta)- or C^4' (para)-position of the terminal phenyl ring, and the substituent effect on mesophase formation was studied. The compounds were characterized by ¹H and ¹³C NMR spectroscopy and elemental analysis, and the mesomorphic behavior of the compounds was characterized and studied by differential scanning calorimetry, polarizing optical microscopy and powder X-ray diffraction. Most of the compounds were mesogenic at room temperature, and the mesophases were assigned as lamellar columnar (Col_L) phases, as expected for disk-like molecules. The results also revealed that compounds with a para-substituent (1a; except for -OCH₃) at the C^4'-position, exhibited higher clearing temperatures and wider temperature mesophase ranges than those of compounds with a meta-substituent (1b) at the C^3'-position. The higher clearing temperatures may be attributed to stronger dipolar interactions resulting from a greater resonance effect with the central core for para-substitution than for meta-substitution. The results also indicated that the columnar mesophases observed show a correlation with the electronic properties of the substituents; compounds containing electron-withdrawing substituents (X=F, Cl, Br, I, NHSO₂CF₃) also have higher clearing temperatures than compounds containing electron-donating substituents (X=Me, Et, OMe).     

Influence of peripheral alkyl chain length on the mesomorphic behaviours of hexasubstituted triphenylene 2,3-dicarboxylic esters

A comparative study of our established synthetic approaches to hexasubsituted triphenylenes 2,3-dicarboxylic esters containing four identical β-alkoxy and two adjacent β-alkoxycarbonyl side chains shows that the phase behaviours of small-sized discotic liquid crystals can be tailored over a wide range by simply varying the length of the peripheral alkyl chains. All the prepared esters in two series were observed to form a single hexagonal columnar phase, except for Tp4-1 having four β-butyloxy and two adjacent β-methoxycarbonyl chains which displays two columnar mesophase behaviours with a transition from the columnar plastic phase to hexagonal columnar phase. A significant difference between the two mesophase was observed in the variable temperature X-ray diffraction studies, and the mesophase assignment was also confirmed by polarising optical microscopy and differential scanning calorimetry. Moreover, the prepared esters in each series display the general trend of decreasing clearing temperature upon increasing alkoxy or alkoxycarbonyl chains length. The intermediate triphenylene 2,3-dicarboxylic acids were also found not only to exhibit columnar hexagonal mesophase over a narrower temperature range by maintaining high melting and clearing points but also to form organogel on mixing with toluene or dichloromethane with the assistance of hydrogen bonding.     

Synthesis, mesomorphic and optical properties of isothiocyanatotolanes

The synthesis, mesomorphic properties and UV absorption spectra of laterally fluorine substituted, and the corresponding unsubstituted, 4'-alkyl-, 4'-alkoxy-, 4'-alkylcyclohexyl-, 4'-alkylbicyclo [2,2,2]octyl- and 4'-alkylcyclohexylethyl-4-isothiocyanatotolanes are described. Multicomponent broad range nematic mixtures with birefringence values higher than 0.4 and moderate viscosities are developed.