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.     

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.     

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.     

Molecular and crystal structure of 4′-cyanobenzo-15-crown-5

The crystal structure of 4′-cyanobenzo-15-crown-5 is determined by X-ray diffraction. The crystallographic parameters of single crystals are as follows: a = 40.479(6) Å, b = 8.821(2) Å, c = 8.484(2) Å, β = 93.94(2)°, V = 3022.2 ų, Z = 8, d _calcd = 1.27 g/cm³, and space group C2/c. The structure is solved by the direct method and refined by the least-squares procedure to R = 0.068. The conformation of the macrocycle in 4′-cyano-B15C5 is described by the a-a-g ^? -a-a-g-g ^? -a-a-g-a-g-a-a-s sequence of torsion angles.     

Structure of a new crystal modification of the bacterial NAD-dependent formate dehydrogenase with a resolution of 2.1 Å

Formate dehydrogenase (FDG) from methylotrophic bacteria Pseudomonas sp. 101 catalyzes the reaction of oxidation of the formate ion to carbon dioxide, which is accompanied by the reduction of nicotinamid adenine dinucleotide (NAD⁺). The structures of the apo and holo (enzyme-NAD-azide triple complex) forms of the enzyme were determined earlier. In an attempt to prepare a complex of FDG with the product of the enzymatic reaction (NADH), a new crystal modification of FDG is obtained (space group P4₂2₁2, a = b = 93.3 Å, c = 103.05 Å). The FDG structure is solved by the molecular replacement method and refined to R = 20.7%. The asymmetric part of the unit cell contains one FDG molecule. In contrast to the previously studied FDG structures, the biologically active dimer is formed by the crystallographic rotation axis. A comparative structural analysis of the studied form with the apo and holo forms of the enzyme is performed. The influence of the molecular structure on the environment in the crystal is investigated.     

Molecular and crystal structure of liquid crystalline p-octyloxyphenyl p′-pentyloxybenzoate

The crystal and molecular structure of p-octyloxyphenyl p′-pentyloxybenzoate C₅H₁₁-O-C₆H₄-C(O)-O-C₆H₄-O-C₈H₁₇, which forms a nematic mesophase upon melting, was determined by X-ray diffraction. There is one system of weak directional intermolecular C-H…π interactions responsible for the formation of the nematic phase in these crystals.     

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 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)°.     

X-ray crystal and molecular structure of 2,3-dideoxy-4-thio-d-arabino-heptonic acid 1,4-lactone: a key intermediate for syntheses of 2′, 3′-dideoxy-4′-thio-l-nucleosides

The structure of 2,3-dideoxy-4-thio-d-arabino-heptonic acid 1,4-lactone has been determined by X-ray diffraction. Crystals of the compound are orthorhombic, space groupP2₁2₁2₁, with cell dimensionsa=11.555(5),b=10.451(5),c=9.604(5) Å, andZ=4. The diffraction experiment has allowed to assign the absolute configuration (4R, 5R, 6R) to the chiral centers of the molecule.     

Structure of 2,2′-bis(3-allyl-4-cyanatophenyl)isopropylidene

The structure of the title compound (I) was determined by direct methods using MoK diffractometer data, and refined by full-matrix least squares toR=0.066 for 1536 reflections (I3 (I)). The structure shows a central tetrahedral carbon atom surrounded by two methyl and two 3-allyl-4-cyanatophenyl groups. The geometry of the cyanato group in this molecule compares well with those in 2,2-bis(4-cyanatophenyl)isopropylideneII) and 4-chloro-3,5-dimethyl-phenylcyanate (III), the only other examples of organic compounds bearing the cyanato moiety in the Cambridge Crystallographic Database (V.3).     

Polarisation‐independent liquid crystal devices

Liquid crystal (LC) devices can be used as amplitude modulators and phase modulators. Most LC devices are polarisation‐dependent and require at least one polariser. As a result, the optical efficiency is greatly reduced. In this paper, we review some of our recently developed polarisation‐independent LC devices. For amplitude modulation, we report two polariser‐free devices which combine light scattering with dye absorption: dye‐doped polymer‐dispersed liquid crystal (PDLC) and dye‐doped LC gels. For phase modulation, we also present two examples: residual phase type, e.g., voltage‐biased PDLC, Polymer‐Stabilised Cholesteric Texture (PSCT), and homeotropic LC gels; and double‐layered structure, such as thin polymer film‐separated orthogonal LC layers, and double‐layered LC gels. Potential applications of these polarisation‐independent LC devices for displays, laser beam steering and adaptive optics are emphasised.     

Molecular and crystal structures of mesomorphic aromatic esters: I. Structure of two isomers, p-butoxyphenyl p′-hexyloxybenzoate and p-hexyloxyphenyl p′-butoxybenzoate

Two isomers, p-butoxyphenyl p′-hexyloxybenzoate (1) and p-hexyloxyphenyl p′-butoxybenzoate (2), are studied by X-ray diffraction. Crystals 1 contain two crystallographically independent molecules, which differ in the conformation of one of their side chains. In both compounds, bond lengths and angles have standard values. The geometry of the central fragment Ph-Est-Ph is essentially the same in both isomers. One of the benzene rings is coplanar with the Est group, and the other ring, which is linked with this group through the oxygen atom, is almost perpendicular to the Est plane. In crystal 1, molecules are packed in such a fashion that, in any pair of neighboring molecules, the most closely spaced benzene rings are nearly perpendicular to each other, which corresponds to a weak C-H?π interaction. In the crystal packing of 2, neither perpendicular nor stacking motifs are observed. The supramolecular architecture of this compound is determined by directional specific interactions of the hydrogen bond type between the C-H benzene fragment and the ester oxygen atom of the neighboring molecule.     

Synthesis and crystal structure of 1,1′-di(ethylpropionato)-2,2′-biimidazole, a macromolecular precursor

1,1,-Di(ethylpropionato)-2,2-biimidazole, C₁₆H₂₂N₄O₄, crystallizes from ice-cold ethanol in the space group P , with a = 4.6742(9), b = 9.1119(13), c = 10.175(2) Å, = 96.22(1), = 96.29(2), = 97.53(1)°, and Z = 1. The molecule crystallizes with coplanar rings and the substituents assume a trans conformation with a center of inversion between the bridging carbon atoms.     

Crystal Structure of Mesogenic Material III Nematogenic 4–(4′-EthoxyphenyIazo)PhenyI Undecylenate

The crystal structure of 4–(4′-ethoxyphenylazo)phenyl undecylenate has been determined by direct methods. The compound crystallizes in space group P2₁/n with a = 5.914(1), b = 15.143(3), c = 25.819(2)A° and β = 91.450(2)°. The structure was refined to R = 0.0412 for 1998 observed reflections. The molecule is almost linear and planar. The angle between the two phenyl rings is 3.996°. The pairs of molecules related by a centre of symmetry form an imbricated arrangement.     

X-ray structure analysis of 4-cyano-4′-<Emphasis Type="Italic">n</Emphasis>-undecyloxybiphenyl

The structure of a liquid crystal of 4-cyano-4′-n-undecyloxybiphenyl (C₂₄H₃₁NO) is determined by X-ray diffraction. The compound crystallizes in the monoclinic crystal system (space group C2/c) with the unit cell parameters a = 84.108(7) Å, b = 7.159(2) Å, c = 6.922(2) Å, and β = 91.6(4)°. The structure has been solved by direct methods and refined to the residual index R₁ = 0.067. Both phenyl rings are almost planar, and the dihedral angle between these rings is 31.5(6)°.     

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.     

Synthesis and crystal structure of 1-(1′,3′-dimethyl-5′-chloropyrazol-4′-carbonyl′-3-(2′-chlorophenyl)-5-amino-4-cyanopyrazole

The title compound 1-(1,3-dimethyl-5-chloropyrazol-4-carbonyl)-3-(2-chlorophenyl)-5-amino-4-cyanopyrazole (C₁₆H₁₂Cl₂N₆O) has been synthesized and characterized by X-ray diffraction: Triclinic, space group P1, with a = 8.6712(8) Å, b = 9.5091(10) Å, c = 11.2170(11) Å = 71.531(2)°, = 84.683(2)°, = 74.099(2)° Z = 2; V = 843.7(14) ų. C(10), O(1), C(11), and N(2) atoms are coplanar with the average deviation of 0.0071 Å, which form 11.03° and 43.93° dihedral angles with pyrazole planes (I) and (II), respectively.     

Optical and dielectric properties of an isothiocyanato liquid crystal compound and comparison of its behavior with that of a homologous member

The properties of an isothiocyanato liquid crystal compound (code name S1) has been studied with a view to compare its behavior with that of another member of its homologous series (code name S5). Optical properties, such as refractive index, polarisability, and their anisotropies, have been evaluated with varying temperature and the orientational order experimentally determined from the study of polarisability anisotropy and compared with theoretically computed values. Dielectric studies have been conducted to determine not only the dielectric anisotropy but also the effective molecular dipole moment and its temperature dependence. The temperature variation of the angle of inclination (β) of molecular dipole moment with the director direction has also been determined and compared with that of S5. In order to determine the nature of molecular association in the mesophase, the molecular correlation factor (g) has been estimated from the measurements of dipole moments of compound in solution and compared with the values obtained for S5.     

Structure of 2-(2′-bromo-5′-nitrostyryl)benzothiazole

The title compound C₁₅H₉BrN₂O₂S (brnsb) is monoclinic, witha=7.730(2),b=26.847(5),c=7.773(2) Å,=117.48(1)°,V=1431(1) ų,Z=4,D _x=1.677,(MoK)=29.9 cm^–1,F(000)=720,T=298K in space groupP2₁/c. The structure was solved by heavy atom and Fourier methods and refined toR=0.034 for 1776 unique observed reflections. The molecule is nearly planar, with a dihedral angle of only 3.8(1.1)° between the benzothiazole and phenyl rings. The C-S-C angle in the thiazole ring is 89.0°, while the C-N-C angle in that ring is 111.5(3)°.     

Chemical preparation and crystal structure of 6′-butoxy-2,6-diamino-3,3′azo-dipyridine monohydrate

Chemical preparation, X-ray single crystal, and calorimetric studies of C₁₄H₁₈N₆O·H₂O are described. The compound crystallizes in the triclinic space group, P with unit cell dimensions: a = 6.2640(3), b = 10.9840(4), c = 12.2220(3) Å, = 105.03(2), = 96.96(2), = 101.6(2)°, V = 712.10(5) ų, and Z = 2. The 6-butoxy-2,6-diamino-3,3-azo-dipyridine monohydrate structure is built up from organic layers parallel to the (120) plane linked via O—H···N bond.