Orientational Distribution Function and Order Parameters of Two 4′-Alkoxy-4-Cyanobiphenyls in Mesomorphic Phase

X-ray diffraction studies on samples of 4′-Pentyloxy-4-Cyanobiphenyl and 4′-Octyloxy-4-Cyanobiphenyl over the entire mesomorphic range are reported in this paper. A magnetic field was used to align samples. The orientational distribution functions f(β) have been calculated from the angular distribution of X-ray intensities. Orientational order parameters ( P ₂) and ( P ₄) have been calculated and compared with Maier-Saupe theoretical values. Expressions for the angular part of the pseudopotentials have been obtained from the temperature variation of f(β). The intermolecular distances D have been calculated from the experimental data and it is found that D is significantly smaller for well aligned samples. The apparent molecular length in the nematic phase and the layer thickness in the smectic phase have also been determined and are found to be about 1.4 times larger than the true molecular length in the fully extended form. This is in accordance with the findings from other cyano compounds.     

Structure of a liquid crystal of 4-cyano-4′-n-octyloxybiphenyl

The structure of a liquid crystal of 4-cyano-4′-n-octyloxybiphenyl (C₂₁H₂₅NO) is determined by X-ray diffraction analysis. The compound crystallizes in the triclinic crystal system with unit cell parameters a = 7.322(1) Å, b = 12.693(3) Å, c = 20.393(2) Å, α = 92.45(1)°, β = 99.96(1)°, γ = 99.35(2)°, and space group $P\bar 1$ . The structure is solved by the direct method and refined to R = 0.057. Two independent molecules are located in the asymmetric unit. No short intermolecular contacts are observed in the crystal packing.     

The Synthesis of Deuteriated 4-n-Alkyl-4′-Cyanobiphenyls

A single synthetic route for chain-deuteriated, totally ring-deuteriated, or per-deuteriated 4-n-alkyl-4′-cyanobiphenyls has been developed. This new route gives better yields than the previously reported route for the synthesis of 4-cyano-4′-n-pentyl-d₁₁-biphenyl and also eliminates the main “impurity” present in the final product. The synthesis of 4-cyano-4′-n-pentyl-d₁₁-2′,3′,5′,6′-tetradeuteriobiphenyl is also reported.     

Crystal and molecular structure of 4′-hexyloxyphenyl 4-pentylbenzoate

The molecular and crystal structure of 4??-hexyloxyphenyl 4-pentylbenzoate, C₆H₁₃O-C₆H₄-COO-C₆H₄-C₅H₁₁, which is a liquid-crystal compound, was determined by X-ray diffraction. This compound forms a nematic phase upon melting. The crystal contains three crystallographically independent molecules. In one of them, the alkyl chain is disordered. This is indicative of the looseness of the crystal packing in the aliphatic region. The crystal structure is stabilized by the following two types of weak directional interactions: hydrogen bonds with the participation of the terminal O atom of the ester group and the C-H group of one of the benzene rings and C-H????-system interactions. Only one of the three independent molecules is involved in the latter type of interactions. Hence, the structurization of the mesophase is most likely determined by hydrogen bonding.     

Molecular and crystal structures of 4-acylphenyl 4′-alkyloxybenzoates

The crystal structures of four liquid-crystal (LC) compounds belonging to 4-acylphenyl 4′-alkyloxybenzoates with the general formula C _n H_{2n + 1}-C(O)-C₆H₄-O-C(O)-C₆H₄-O-C _m H_{2m + 1} numbered as 1/6, 1/7,2/7, and 3/7 (the numbers in the code indicate the ratios of the numbers of alkyl-chain units, n/m) are determined. Compounds 1/6 and 1/7 form smectic and nematic phases, but they are monotropic mesogens, whereas compounds 2/7 and 3/7 form only an enantiotropic smectic phase. Compound 3/7 crystallizes in two crystal modifications—triclinic with Z′ = 2 (3/7 _tr ) and monoclinic with Z′ = 4 (sp. gr. P2, 3/7 _mon ). All crystals consist of alternating aromatic and aliphatic regions and are characterized by the presence of weak directional interactions, such as C-H...O hydrogen bonds and π-stacking interactions. This provides the necessary conditions for the formation of a mesophase, and the existence of two types of structure-forming units is in line with the formation of a smectic phase. An explanation is proposed for the monotropic properties of 1/6 and 1/7.     

X-ray diffraction study of mesogenic 4-methoxyphenyl-4′-n-nonyloxybenzoate

4-methoxyphenyl-4′-n-nonyloxybenzoate have been investigated by single crystal X-ray structural analysis. Crystal packing of the compounds does not represent a precursor of the mesophse although the typical for liquid crystal compounds separation of crystal packing on aromatic and aliphatic areas is observed here. Possible reason for monotropic properties are discussed.     

X-ray structure and NMR assignment of 4-methoxy-4′-methylthio-3,3′-diquinolinyl sulfidea

The title compound (C₂₀H₁₆N₂OS₂) is monoclinic, witha=7.786(3).,b=13.252(3),c=17.162(4) Å, =99.16(3)° and space groupP2₁/n. Two quinoline moieties are nearly perpendicular to each other (112.9(2)°). Both methoxy and methylthio groups are trans-orientated with the respect to the C(3)–S(1)–C(13) plane. Two pairs of the heteroatoms in ortho-positions are in very close contact. The conformation of the molecule explains an unusual¹H NMR spectrum     

Physical Studies of Homologous 4-Cyanophenyl Esters of 4′- n-Alkylcinnamic Acids

The mean polarizabilities of homologous series of nematic liquid crystals of 4-cyanophenyl esters of 4′- n-alkylcinnamic acids are evaluated by using the MLδP method. From these polarizabilities the mean diamagnetic susceptibilities of the liquid crystals are also calculated. The orientational order parameters of these compounds are also estimated using the Vuks and Neugebauer methods. The variation of the order parameter with temperature is discussed.     

X-ray structure of 4-chloro-3′-methylthio-3,4′-diquinolinyl sulfide

The title compound crystallizes in a monoclinic space groupP2₁/n witha=9.524(3),b=6.782(2),c=26.217(6) Å, =92.52(4)°. The values of the Cl...S and S...S distances are well below the sum of the van der Waals radii of the heteroatoms. Also, the Cl–C–C(S) and (Cl)C–C–S bond angles are below the standard 120°. This indicates a attractive interaction between both pairs ofortho-situated heteroatoms.Part XXXVIII in the Series of Azinyl Sulfides.     

Elastic and Optical Properties of Some 4′-n-Alkyl-4-Cyanobiphenyls

The bend elastic constants (k ₃₃) and order parameters (S) derived from optical measurements in the nematic phase of pentlyl, hexyl, heptyl and octyl cyanobiphenyls (5CB, 6CB, 7CB and 8CB respectively) are reported. The odd-even effect is clearly seen in the K ₃₃ values of all four compounds and in the S values of the first three. 5CB, 6CB and 7CB show only the nematic mesophase but their elastic constants indicate the existence of smectic-like short range order. For example, even the lowest homologue, 5CB, does not obey the law k ₃₃ ∞ S ² given by the mean field throry. 7CB, has about the same order parameter as 5CB but a much higher elastic constant. 8CB, which shows a smectic A phase as well, exhibits a lower k ₃₃ than 7CB near the nematic-isotropic transition point but a pronounced pretransitional increase near the A-N transition.     

Investigation of the Homologous Series of 4-Acetyl-4′-n-Alkanoyloxyazobenzenes by X-ray Diffraction

This paper reports an investigation by X-ray diffraction of the homologous series of liquid crystalline 4-acetyl-4′-n-alkanoyloxyazobenzenes. By using two independent parameters, namely the temperature and the paraffinic chain length, it was possible to obtain some structural information on two solid phases for comparison with a previously reported model for the S_A phase of the same series. In particular, the molecular layer thickness and, by using previously reported dilatometric data, the aromatic sublayer thickness, the methylene group thickness, the molecular area and the aromatic stem inclination angle were obtained for the different phases.     

Investigation of the Homologous Series of 4-Propionyl–4′-n-Alkanoyloxyazobenzenes by X-Ray Diffraction

A study of the homologous series of liquid cristalline 4-propionyl-4′-n-alkanoyloxyazobenzenes was performed by x-ray diffraction. Two indipendent parame ters were used, namely the temperature and the paraffinic chain length, in order to obtain some structural in formation. In particular the molecular layer thickness was obtained as a function of the temperature for the different phases and different homologous. A linear de pendence of the molecular layer thickness as a function of chain length was found for the crystalline phase as it was previously observed for the smectic A phase. By comparison of the present data with those of the series 4-acetyl-4′-n-alkanoyloxyazobenzenes, a bilayer molecular organization similar to that of the smectic A phase appears as very probable also for the crystalline phase.     

Synthesis and Some Properties of 3-Fluoro-4-Cyanophenyl 4′-n-alkylbenzoates

A series of 3-fluoro-4-cyanophenyl 4′-n-alkylbenzoates, which show monotropic nematic phases, was prepared and their transition temperatures and melting enthalpies were measured. The 3-fluoro-4-cyanophenyl 4′-n-propylbenzoate, 3-chloro-4-cyanophenyl 4′-n-propylbenzoate and 4-cyanophenyl 4′-n-propylbenzoate were mixed with a nematic mixture (A) of 4-n-alkoxyphenyl 4′-n-alkylcyclohexane-1′-carboxylates. 3-Fluoro-4-cyanophenyl 4′-n-propylbenzoate decreases the N-1 transition temperature less, increases the birefringence more, and increases the bulk viscosity less than 3-chloro-4-cyanophenyl 4′-n-propylbenzoate, and reduces the threshold voltage to the greatest extent. The dielectric anisotropies of 3-fluoro-4-cyanophenyl 4′-n-propylbenzoate and 4-cyanophenyl 4′-n-propylbenzoate determined from a series of solutions of the compounds in nematic mixture (A) are 35.9 and 29.6, respectively.     

Crystal Structure of 3′-(4-Methoxyphenyl)-2-Phenyl-4′-(4-Ethoxyphenyl)-1,2-Dihydro-4H,4′H-Spiro [Isoquinoline-3,5′-Isoxazol]-4-One

The title compound, 3′-(4-methoxyphenyl)-2-phenyl-4′-(4-ethoxyphenyl)-1,2-dihydro-4H,4′H-spiro[isoquinoline-3,5′-isoxazol]-4-one was synthesized from the reaction of dipolarophile with p-methoxybenzadoxime in the presence of sodium hypochlorite in chloroform solution. The structure of the synthesized compound was determined by IR, ¹H NMR, mass spectroscopic data, ¹³C NMR spectroscopy, elemental analysis and X-ray crystallography. The structure was solved in monoclinic, space group C2/c with a = 21.941 (4), b = 17.233 (3), c = 15.404 (3) Å, β = 122.193 (2), V = 4928.9 (16) Å³, Z = 8 and with R_int = 0.154. The geometry of the title compound showed that the piperidine ring adopts a half-chair conformation. In the crystal structure, molecules are linked by C–H···O and C–H···N contacts. Weak C–H···π interactions plays an important role in stabilizing the supramolecular structure.     

Order Parameters of β-Substituted Anthraquinone Dyes I: 1-Amino-4-Hydroxyanthraquinone Derivatives

A study is presented of the optical order parameters and spectroscopic properties of I-amino-4-hydroxyanthraquinone derivatives containing various substituents in the 2-position in a nematic liquid crystalline mixture composed of cyanophenylcyclohexane derivatives. The results are discussed in terms of the effects of the dye structure on the order parameters. By introducing a-SCH₂-group into the 2-position, magenta dyes have been obtained which show high order parameters and solubilities. In addition, preliminary data on the solubility and photostability of the dyes are reported.     

Crystal and Molecular Structure of the Nematogenic Compound 4′-Cyanophenyl-4-n-Pentoxybenzoate

The title compound with the formula C₅H₁₁O-C₆H₄-COO-C₆H₄-CN (CPPOB) crystallizes in the orthorhombic space group Pnam with a = 16.465 Å, b = 13.577 Å, c = 7. 621 Å and four molecules per unit cell. The structure has been solved by direct methods and refined to a final R value of 0.050. The CPPOB molecules have exact C_s symmetry as a consequence of their location on crystallographic mirror symmetry planes, the benzene ring to which the cyano group is attatched has a perpendicular orientation to the other ring in the plane. The molecules adopt a nearly optimal stretched form, neighbouring molecules make an angle of 35.2°. The results are discussed in relation to the mesomorphic behaviour of CPPOB.     

Structure of 2,2′-bis(4-cyanatophenyl)isopropylidene

The title compound is monoclinic:a=13.345(3),b=11.393(2),c=10.046(5)Å,=108.48(2)°,Z=4,P2₁/c. The structure was determined by direct methods, using MoK diffractometer data, and refined by full-matrix least squares toR=0.045 for 1463 reflections. The structure shows a central tetrahedral carbon atom surrounded by two methyl and two phenylcyanate groups. The geometry of the cyanate group compares well with that in 4-chloro-3,5-dimethyl-phenyl cyanate, the only example of an organic cyanate in the Cambridge Crystallographic database (V.3). The intermolecular nitrile, C-N, distances were examined for evidence of a possible dimerization interaction; no significant distances were found.     

Synthesis and crystal structure of 7-ethoxyl-4′-hydroxyisoflavone

7-Ethoxyl-4-hydroxyisoflavone was prepared and its crystal structure was examined by X-ray diffraction. Crystallization of the title compound occurs in the monoclinic, space group P2(1)/c with a = 11.144(2) Å, b = 10.209(1) Å, c = 13.191(2) Å, = 113.43(1) and Z = 4. The molecular structure of title compound consists of a benzopyranone moiety, a phenyl moiety, a hydroxyl and an ethoxyl group. The benzopyranone ring is not coplanar with the phenyl ring, the dihedral angle being 46.75. The ethoxyl group is nearly coplanar with its corresponding ring with the torsion angle 175.23(2). Three kinds of hydrogen bond and two kinds of aromatic stacking interaction link the title compounds into a three-dimensional networking structure.     

Crystal and molecular structure of 2′,4′-dimethoxyflavone

C₁₇H₁₄O₄,M _r =282.3, triclinic,P-1,a=8.469(3),b=8.516(2),c=20.425(8)Å,=84.95(3),=81.98(3), =70.47(2)°,V=1373(13)ų,Z=4,D _x =1.365 g cm^–3, (MoK )=0.71069 Å,=0.91 cm^–1,F(000)=592,T=294K,R=0.038 for 3577 observed reflections (F>3 (F)). The asymmetric unit is composed of two molecules. These two molecules, which are in planar conformations, differ in 4-methoxyl group orientation. Short intramolecular contacts are found between the -benzopyran portion and the dimethoxyphenyl ring.     

Structure of 1-ethyl-2-(2′-chloro-4′-nitrostyryl)benzimidazole

The title compound C₁₇H₁₄ClN₃O₂ (et-4-nsbiz) is monoclinic, witha=12.240(2),b=12.144(4),c=10.544(4)Å,=100.09(2)°,V=1543(1)ų,Z=4,D _x =1.411 g cm^–3, (MoK)=0.71073Å,=2.57 cm^–1,F(000)=680,M _r =327.77,T=298K. The structure was solved by heavy atom and Fourier methods and refined toR=0.049 for 1503 unique observed reflections in space groupP2₁/c. Except for the ethyl group, the molecule is almost planar, with a dihedral angle of 9.5(5)° between the benzimidazole and phenyl rings. The dihedral angle between the ethyl group and the benzimidazole ring to which it is attached is 91.5(2)°.