Leaning induced layer undulated tilted smectic phase of asymmetric bent-core liquid crystals.

We report the synthesis and experimental studies on the liquid crystalline phase of a homologous series of compounds comprised of strongly asymmetric bent-core banana shaped molecules. Our x-ray diffraction studies clearly indicate that the compounds exhibit a frustrated tilted smectic phase with layer undulated structure. The low value of the dielectric constant as well as switching current measurements indicate the absence of polarization in this layer undulated phase. In spite of the absence of polarization, a planar aligned sample can be transformed irreversibly to a higher birefringent texture on the application of a high electric field. The zero field texture can only be retrieved by heating the sample to the isotropic phase and cooling it subsequently to the mesophase. We propose a double tilted smectic structure having layer undulation to account for the experimental observations with the layer undulation arising due to the leaning of the molecules in the layer.

6-Cyanona-phthalen-2-yl 4-hexyl-benzo-ate.

In the title compound, C24H23NO2, a whole mol-ecule is disordered over two sets of sites with occupancies in a ratio of 0.692 (6):0.308 (6). In the major disorder component, the naphthalene ring system forms a dihedral angle of 68.6 (5)° with the benzene ring. The corresponding angle in the minor component is 81.6 (10)°. In the crystal, mol-ecules are linked into chains propagating along the b-axis direction via weak C-H⋯O hydrogen bonds. The crystal packing is further consolidated by weak C-H⋯π inter-actions.

6-(Hex-5-en-yloxy)naphthalene-2-carb-oxy-lic acid.

The asymmetric unit of the title compound, C17H18O3, comprises three independent mol-ecules with similar geometries. In each mol-ecule, the carbonyl group is twisted away from the napthalene ring system, making dihedral angles of 1.0 (2), 1.05 (19)° and 1.5 (2)°. The butene group in all three mol-ecules are disordered over two sets of sites, with a refined occupancy ratio of 0.664 (6):0.336 (6). In the crystal, mol-ecules are oriented with respect to their carbonyl groups, forming head-to-head dimers via O-H⋯O hydrogen bonds. Adjacent dimers are further inter-connected by C-H⋯O hydrogen bonds into chains along the a-axis direction. The crystal structure is further stabilized by weak C-H⋯π inter-actions.

Synthesis, crystal structure and Hirshfeld surface analysis of 4'-cyano-[1,1'-biphen-yl]-4-yl 3-(benz-yloxy)benzoate.

In the title compound, C27H19O3N, the dihedral angle between the aromatic rings of the biphenyl unit is 38.14 (2)° and the C-O-C-C torsion angle in the benz-yloxy benzene fragment is 179.1 (2)°. In the crystal, the mol-ecules are linked by weak C-H⋯O inter-actions forming S(9) chains propagating along [010]. The most important contributions to the Hirshfeld surface arise from H⋯H (32.4%) and C⋯H/H⋯C (37.0%) contacts.

4-(Dec-yloxy)phenyl 2-oxo-7-trifluoro-methyl-2H-chromene-3-carboxyl-ate.

The title compound, C27H29F3O5, is a liquid crystal (LC) and exhibits enanti-otropic SmA phase transitions. In the crystal, the dihedral angle between the 2H-chromene ring system and the benzene ring is 62.97 (2)°. The three F atoms of the -CF3 group are disordered over two sets of sites with occupancy factors 0.71 (4):0.29 (4). In the crystal, pairs of C-H⋯O hydrogen bonds form inversion dimers and generate R 2 (2)(10) rings. The structure also features C-H⋯F and C-H⋯π inter-actions along [100] and [010], respectively.

4-(Oct-yloxy)phenyl 2-oxo-2H-chromene-3-carboxyl-ate.

In the title compound, C(24)H(26)O(5), the 2H-chromene ring system is essentially planar, with a maximum deviation of 0.029 (2) Šfrom the best-fit mean plane incorporating both rings. The dihedral angle between the 2H-chromene ring system and the benzene ring is 21.00 (1)°. In the crystal, pairs of C-H⋯O hydrogen bonds generate an R(2) (2)(8) ring pattern. These contacts are bolstered by weaker bifurcated C-H⋯O hydrogen bonds.

4'-Cyano-biphenyl-4-yl 7-diethyl-amino-2-oxo-2H-chromene-3-carboxyl-ate.

In the title compound, C(27)H(22)N(2)O(4), the dihedral angles between the central benzene ring and the cyano-benzene ring and the 2H-coumarin ring system (r.m.s. deviation = 0.014 Å) are 22.95 (11) and 75.59 (8)°, respectively. Both terminal C atoms of the pendant diethyl-amino group lie to the same side of the coumarin ring system [deviations = 1.366 (2) and 1.266 (2) Å]. In the crystal, mol-ecules are linked by C-H⋯O and C-H⋯N hydrogen bonds and a C-H⋯π inter-action, generating a three-dimensional network.

Synthesis, crystal structure and Hirshfeld surface analysis of naphthalene-2,3-diyl bis-(3-benz-yl-oxy)benzoate.

In the title compound, C38H28O6, the dihedral angles between the naphthalene ring system and its pendant benz-yloxy rings A and B are 88.05 (7) and 80.84 (7)°, respectively. The dihedral angles between the A and B rings and their attached phenyl rings are 49.15 (8) and 80.78 (8)°, respectively. In the extended structure, the mol-ecules are linked by weak C-H⋯O and C-H⋯π hydrogen bonds, and π-π stacking inter-actions, which variously generate C(11) chains and R 2 2(12) loops as part of a three-dimensional network. The Hirshfeld surface [fingerprint contributions = H⋯H (42.3%), C⋯H/H⋯C (40.3%) and O⋯H/H⋯O (15.7%)] and inter-molecular inter-action energies are reported, with dispersion (E dis = -428.6 kJ mol-1) being the major contributor.

Methyl 4-benz-yloxy-2-hy-droxy-benzoate.

In the title compound, C15H14O4, the dihedral angle between the benzene rings is 67.18 (8)°. The Ca-Cm-O-Ca (a = aromatic and m = methyl-ene) torsion angle is 172.6 (3)° and an intra-molecular O-H⋯O hydrogen bond generates an S(6) ring. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds into zigzag chains propagating in [001] and C-H⋯π inter-actions also occur.

4-Nitro-phenyl 4-hy-droxy-3-methyl-benzoate.

The asymmetric unit of the title compound, C14H11NO5, contains two independent mol-ecules in which the dihedral angles between the benzene rings are 89.27 (16) and 77.14 (12)°. In the crystal, mol-ecules are linked by O-H⋯O hydrogen bonds, generating C(8) chains propagating in [010] for one mol-ecule and [001] C(8) chains for the other. The chains are connected by C-H⋯O hydrogen bonds and π-π inter-actions [shortest centroid-centroid distance = 3.5908 (12)°], generating a three-dimensional network.

Crystal structure and Hirshfeld surface analysis of 3-({4-[(4-cyano-phen-oxy)carbon-yl]phen-oxy}carbon-yl)phenyl 4-(benz-yloxy)-3-chloro-benzoate.

The title compound, C35H22ClNO7, is a non-liquid crystal with a bent-shaped mol-ecule. The dihedral angles between adjacent aromatic rings in the mol-ecule (starting from the cyano-benzene ring) are 72.61 (2), 87.69 (4), 64.08 (2) and 88.23 (2)°, indicating that adjacent rings are close to perpendicular to each other. In the crystal, the mol-ecules are linked by weak C-H⋯N and C-H⋯π inter-actions, thereby forming a two-dimensional supra-molecular architecture in the ac plane. The most important contributions to the crystal packing arise from H⋯H (59.3%), S⋯H (27.4%) and O⋯H (7.5%) inter-actions, as determined by a Hirshfeld surface analysis.

4-(Benz-yloxy)phenyl 4-hexa-dec-yloxy-3-meth-oxy-benzoate.

In the title compound, C(37)H(50)O(5), the central benzene ring makes dihedral angles of 39.72 (14) and 64.43 (13)° with the benzyl and 3-meth-oxy-benzoate rings, respectively. The crystal structure is stabilized by inter-molecular C-H⋯π inter-actions involving the central benzene ring and the benzene ring closest to the aliphatic chain.

4-Eth-oxy-phenyl 4-[(meth-oxy-carbon-yl)-oxy]benzoate.

In the title compound, C(17)H(16)O(6), the two benzene rings form a dihedral angle of 54.95 (10)°. Only weak inter-molecular inter-actions are present in the crystal structure, viz. C-H⋯O hydrogen bonds and C-H⋯π inter-actions involving one of the benzene rings.

4-Decyl-phenyl 4-benz-yloxy-3-methyl-benzoate.

In the title compound, C(31)H(38)O(3), the central benzene ring makes dihedral angles of 66.06 (9) and 65.21 (8)°, respectively, with the benzyl and 4-decyl-phenyl rings.

Novel banana-discotic hybrid architectures.

Here we present the design and synthesis of novel banana-discotic dimers and banana-bridged discotic dimers. The chemical structures have been characterized by spectral techniques and elemental analysis. The thermal behaviors of the compounds have been investigated by polarizing optical microscopy and differential scanning calorimetry. None of these synthesized compounds exhibit any liquid crystalline property probably because of the incompatibility of the bent-core with the discotic core.

Crystal structure of 4-bromo-phenyl-2-oxo-2H-chromene-3-carboxyl-ate.

In the title compound, C16H9BrO4, the coumarin ring system is approximately planar, with an r.m.s deviation of the ten fitted non-H atoms of 0.031 Å, and forms a dihedral angle of 25.85 (10)° with the bromo-benzene ring. The carbonyl atoms are syn. In the crystal, mol-ecules are connected along [001] via C-H⋯O inter-actions, forming C(6) chains. Neighbouring C(6) chains are connected via several π-π inter-actions [range of centroid-centroid distances = 3.7254 (15)-3.7716 (16) Å], leading to sheets propagating in the bc plane.

Crystal structure of bis-(4-meth-oxy-phenyl) malonate.

The complete mol-ecule of the title compound, C17H16O6, is generated by crystallographic twofold symmetry, with the central methyl-ene C atom lying on the rotation axis. The carbonyl O atom is disordered over two adjacent positions in a 0.63 (3):0.37 (3) ratio and the dihedral angle between the benzene rings in the two halves of the mol-ecule is 79.31 (12)°. In the crystal, mol-ecules are connected by C-H⋯O hydrogen bonds, generating (110) sheets. Very weak intra-sheet C-H⋯π inter-actions are also observed.

Crystal structure of 4-meth-oxy-phenyl 2-oxo-2H-chromene-3-carboxyl-ate.

In the title compound, C17H12O5, the dihedral angle between the planes of the coumarin ring system (r.m.s. deviation = 0.015 Å) and the benzene ring is 48.04 (10)°. The central CO2 group subtends a dihedral angle of 27.15 (11)° with the coumarin ring system and 74.86 (13)° with the benzene ring. In the crystal, mol-ecules are linked by C-H⋯O inter-actions, which generate a three-dimensional network. Very weak C-H⋯π inter-actions are also observed.