Tuning the solid-state emission of liquid crystalline nitro-cyanostilbene by halogen bonding

• Subrata Nath,
• Alexander Kappelt,
• Matthias Spengler,
• Bibhisan Roy,
• Jens Voskuhl and
• Michael Giese

Beilstein J. Org. Chem. 2021, 17, 124–131, doi:10.3762/bjoc.17.13

• alkoxy chain on the halogen bond accepting moiety (NO2-C9 and NO2-C11) displayed an enantiotropic phase behaviour. For the NO2-Cn∙∙∙F4Az assemblies no significant effect of the alkoxy chain length on the transition temperatures was observed. The temperature ranges of the nematic phases are significantly

Thermotropic and lyotropic behaviour of new liquid-crystalline materials with different hydrophilic groups: synthesis and mesomorphic properties

• Alexej Bubnov,
• Miroslav Kašpar,
• Věra Hamplová,
• Ute Dawin and
• Frank Giesselmann

Beilstein J. Org. Chem. 2013, 9, 425–436, doi:10.3762/bjoc.9.45

• . Four of these nonchiral and chiral materials exhibit nematic and chiral nematic phases, respectively. For some molecular structures, smectic phases have also been detected. A contact sample of one of the prepared compounds with diethylene glycol clearly shows the lyotropic behaviour; namely a lamellar

• functional liquid-crystalline materials exhibiting the thermotropic and lyotropic behaviour. Most of these new nonchiral and chiral materials exhibit the thermotropic nematic and chiral nematic phases, respectively. Smectic phases have been detected for the studied materials with the exception of nonchiral

A new family of four-ring bent-core nematic liquid crystals with highly polar transverse and end groups

• Kalpana Upadhyaya,
• Venkatesh Gude,
• Golam Mohiuddin and
• Rao V. S. Nandiraju

Beilstein J. Org. Chem. 2013, 9, 26–35, doi:10.3762/bjoc.9.4

• [27][28][29][30]. The nematic phases exhibited by bent-core compounds are distinctly different from the nematic phases exhibited by rodlike (calamitic) molecules. Recent reports of a nematic phase composed of SmC-type cybotactic clusters [20][21][22][23][24][25] particularly in bent-core compounds

• followed by the optical observation of a biaxial nematic phase [27] motivated the design and synthesis of new bent-core compounds with different functional moieties to exhibit nematic phases. However, there are relatively few examples reported in the literature based on four-ring bent-core or nonlinear

• molecules substantially favour the stabilization of biaxial nematic phases, and (b) the electrostatic interactions between permanent transverse dipoles of bent-core molecules also significantly stabilize the biaxial nematic phases. The introduction of a 2-chloro group in the 1,3-disubstituted phenyl ring of

Liquid-crystalline heterodimesogens and ABA-heterotrimesogens comprising a bent 3,5-diphenyl-1,2,4-oxadiazole central unit

• Govindaswamy Shanker,
• Marko Prehm and
• Carsten Tschierske

Beilstein J. Org. Chem. 2012, 8, 472–485, doi:10.3762/bjoc.8.54

• studied by optical polarizing microscopy (PM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). All dimesogens exhibit broad ranges of cybotactic nematic phases (NcybA and NcybC), in some cases accompanied by additional mesophases (CybA or SmC) at lower temperature. The combination of

• the 3,5-diphenyl-1,2,4-oxadiazole unit with one cyanobiphenyl core leads to the removal of tilted smectic and cybotactic nematic phases (SmC, NcybC), which are replaced by the nontilted CybA phases and nematic phases composed of SmA-type clusters (NcybA). The orthogonal cybotactic nematic phases of

• bent-core mesogens are of special interest for achieving biaxial nematic phases of the orthorhombic type. The orthogonal (NcybA) and skewed (NcybC) cybotactic nematic phases were distinguished by XRD and optical observations. Keywords: bent-core mesogens; cybotactic nematic phases; dimesogen; liquid

Perhydroazulene-based liquid-crystalline materials with smectic phases

• Zakir Hussain,
• Henning Hopf and
• S. Holger Eichhorn

Beilstein J. Org. Chem. 2012, 8, 403–410, doi:10.3762/bjoc.8.44

• . The mesomorphic properties of the new LC compounds were investigated by differential scanning colorimetry, polarizing optical microscopy and X-ray diffraction. We report here on the LC properties of nonchiral materials, which predominantly exhibit smectic phases and display nematic phases only within

• ; nematic phases; smectic phases; Introduction Liquid crystals for display applications have to fulfill a complex, interdependent set of properties [1]. First of all, they must display a broad nematic phase, typically ranging from −30 °C to +80 °C. The absolute value for the dielectric anisotropy Δε should

• synthesized new liquid-crystalline materials with a perhydroazulene core and investigated their stereochemistry by advanced NMR spectroscopic methods. On the basis of the concept that linearity in these molecules results in liquid-crystalline phases, we present data here on smectic as well as nematic phases

Synthesis and mesomorphic properties of calamitic malonates and cyanoacetates tethered to 4-cyanobiphenyls

• Katharina C. Kress,
• Martin Kaller,
• Kirill V. Axenov,
• Stefan Tussetschläger and
• Sabine Laschat

Beilstein J. Org. Chem. 2012, 8, 371–378, doi:10.3762/bjoc.8.40

• with methyl 3-chloro-3-oxopropionate or cyanoacetic acid, giving liquid-crystalline linear malonates and cyanoacetates. These compounds formed monotropic nematic phases at 62 °C down to ambient temperature upon cooling from the isotropic liquid. The mesomorphic properties were investigated by

• axis, but with the molecular arrangement in random positional order [1]. Nematic phases typically display low viscosity [2][3][4]. Due to the long-range orientational order they reveal anisotropic properties. These features make nematic liquid crystals very attractive materials for electronics [5][6][7

• (POM) studies POM observations of compounds 11a,b and 13a,b revealed textures typical for nematic phases, only upon cooling from the isotropic liquid (Figure 3 and Figure 4). Schlieren textures with fourfold brushes were observed for compound 13b at the transition from the isotropic liquid into the

Liquid-crystalline nanoparticles: Hybrid design and mesophase structures

• Gareth L. Nealon,
• Romain Greget,
• Cristina Dominguez,
• Zsuzsanna T. Nagy,
• Daniel Guillon,
• Jean-Louis Gallani and
• Bertrand Donnio

Beilstein J. Org. Chem. 2012, 8, 349–370, doi:10.3762/bjoc.8.39

• LCNPs, and the first such report involved the direct synthesis of 3 nm Au NPs in the presence of a calamitic (cyclohexyl)phenoxy thiol (5, Figure 3) to give a densely packed surface coating (Figure 4a) [60]. The ligand showed both smectic and nematic phases, and the authors claimed that the Au@5 hybrid

• , which is consistent with theoretical treatments [95][96]. This is particularly apparent for systems in which the organic ligand is small relative to the size of the NP, the clearest examples of this are seen for highly anisotropic NPs, which form nematic phases upon suitable functionalisation, whereas

• caused by the increased cohesion between the hybrid NPs due to more efficient interdigitation of the cyanobiphenyl groups. The observation of a second, weak diffusion occurring at around 1.5 nm (NP@20) and 1.8 nm (NP@21) was assigned to weakly correlated cybotactic clusters, as in classical nematic

The interplay of configuration and conformation in helical perylenequinones: Insights from chirality induction in liquid crystals and calculations

• Elisa Frezza,
• Silvia Pieraccini,
• Stefania Mazzini,
• Alberta Ferrarini and
• Gian Piero Spada

Beilstein J. Org. Chem. 2012, 8, 155–163, doi:10.3762/bjoc.8.16

• configuration of the dopant: Enantiomers induce oppositely handed cholesterics. Only in the last few decades has the generation of cholesteric liquid crystals and the amplification of the molecular chirality observed upon doping nematic phases with chiral derivatives attracted great interest in the field of

Self-assembled ordered structures in thin films of HAT5 discotic liquid crystal

• Piero Morales,
• Jan Lagerwall,
• Paolo Vacca,
• Sabine Laschat and
• Giusy Scalia

Beilstein J. Org. Chem. 2010, 6, No. 51, doi:10.3762/bjoc.6.51

• explanation could be that, as the solvent evaporates a concentration is reached at which aggregates of columnar stacks exhibit an organized phase of lyomesomorphic type, like the soft columnar nematic phases of diluted discotics described in other works [16][17][18]. Discotic molecules aggregate in small

Low temperature enantiotropic nematic phases from V-shaped, shape-persistent molecules

• Matthias Lehmann and
• Jens Seltmann

Beilstein J. Org. Chem. 2009, 5, No. 73, doi:10.3762/bjoc.5.73

• engineering; thiadiazoles; V-shaped mesogens; Introduction Most molecules forming nematic liquid crystals, the nematogens, are based on rod-shaped (calamitic), anisometric cores with peripheral flexible chains along the molecular long axis [1]. Nematic phases are the simplest liquid crystalline mesophases

• , in which phase anisotropy of crystals is combined with fluid properties of liquids. In the nematic phases of calamitic mesogens only the molecular long axes are oriented along a so called director [2] and the molecular centres of gravity are distributed like in a liquid. In models, the molecules are

• able to form biaxial nematic phases at an appropriate low temperature [4]. What is a biaxial nematic phase and why is it so interesting? Uniaxial and biaxial phases can be best understood by the property from which this classification originates: the behaviour when light propagates in the material. The

Molecular length distribution and the formation of smectic phases

• Nadia Kapernaum,
• C. Scott Hartley,
• Jeffrey C. Roberts,
• Robert P. Lemieux and
• Frank Giesselmann

Beilstein J. Org. Chem. 2009, 5, No. 65, doi:10.3762/bjoc.5.65

• mixtures. The nematic phases disappeared rapidly, as well as the smectic C phase, while the smectic A phase was the only stable phase over the whole phase diagram. They also found a dramatic decrease of the tilt angle in the remaining SmC phases, until the SmC phases disappeared at a concentration-induced

Novel banana-discotic hybrid architectures

• Hari Krishna Bisoyi,
• H. T. Srinivasa and
• Sandeep Kumar

Beilstein J. Org. Chem. 2009, 5, No. 52, doi:10.3762/bjoc.5.52

• switched in external electric fields. Various new applications of these materials include nonlinear optics, flexoelectricity, photoconductivity, molecular electronics and the design of biaxial nematic phases [8][9]. In addition to various banana phases, these mesogens also display classical nematic

A convenient method for preparing rigid-core ionic liquid crystals

• Julien Fouchet,
• Laurent Douce,
• Benoît Heinrich,
• Richard Welter and
• Alain Louati

Beilstein J. Org. Chem. 2009, 5, No. 51, doi:10.3762/bjoc.5.51

• governs the formation of a multitude of supramolecular architectures depending on the temperature (thermotropic liquid crystals) and/or of the solvent (lyotropic liquid crystals) [7][8]. In the case of the thermotropic liquid crystals the arrangements give rise to nematic phases (molecules are aligned

Chiral amplification in a cyanobiphenyl nematic liquid crystal doped with helicene-like derivatives

• Alberta Ferrarini,
• Silvia Pieraccini,
• Stefano Masiero and
• Gian Piero Spada

Beilstein J. Org. Chem. 2009, 5, No. 50, doi:10.3762/bjoc.5.50

• good solubility in the nematic host and high helical twisting power. Understanding of the mechanism behind chirality transfer from solute molecules to host nematic phases is essential for designing LC-based chiral devices; our and other research groups have investigated this issue (for a selection of

Shape- persistent macrocycle with intraannular alkyl groups: some structural limits of discotic liquid crystals with an inverted structure

• Sigurd Höger,
• Jill Weber,
• Andreas Leppert and
• Volker Enkelmann

Beilstein J. Org. Chem. 2008, 4, No. 1, doi:10.1186/1860-5397-4-1

• mesophases. However, reports about shape-persistent macrocycles with extraannular PAH substituents are absent. If these compounds exhibit liquid crystallinity, the question about the mesogenic element (ring or PAH or both) arises. Additionally, biaxial nematic phases might be observable [31][32]. The