Switchable molecular tweezers: design and applications

• Pablo Msellem,
• Maksym Dekthiarenko,
• Nihal Hadj Seyd and
• Guillaume Vives

Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45

• conversion to the Z open form is achieved, in which the cholesteryl units are oriented in an anti-fashion. This conformational change results in a significant increase in the solvent-accessible surface area. Tweezers 5 were utilized as a dopant for the achiral liquid crystalline material nematic phase 5 (NP5

• ) to produce a chiral nematic phase, whose reflected color can change from green to purple under cross-polarized view upon protonation. This system serves as an elegant example of a macroscopic effect induced by a conformational change at the molecular level. In a different approach where the stimuli

Preparing a liquid crystalline dispersion of carbon nanotubes with high aspect ratio

• Keiko Kojima,
• Nodoka Kosugi,
• Hirokuni Jintoku,
• Kazufumi Kobashi and
• Toshiya Okazaki

Beilstein J. Org. Chem. 2024, 20, 52–58, doi:10.3762/bjoc.20.7

• transition concentrations from isotropic phase to biphasic state, and from biphasic state to nematic phase are lowered, which is consistent with the predictions of the Onsager theory. An aligned DWCNT film was prepared from the DWCNT dispersion by a simple bar-coating method. Regardless of the higher aspect

• ) method [22][23]. The transition concentrations from the isotropic phase to the biphasic state, and from the biphasic state to the nematic phase were inversely proportional to the aspect ratio (L/D) of the SWCNT, following the same trend as the Onsager theory [7][9][11][15][20][23][24]. By using

• dispersions with a higher L/D were successfully prepared utilizing highly crystalline DWCNTs. Indeed, the transition concentrations from the isotropic phase to the biphasic coexisting state and from the biphasic coexisting state to the nematic phase were found to be lower than those in the previous study. In

The influence of intraannular templates on the liquid crystallinity of shape-persistent macrocycles

• Joscha Vollmeyer,
• Ute Baumeister and
• Sigurd Höger

Beilstein J. Org. Chem. 2014, 10, 910–920, doi:10.3762/bjoc.10.89

• °C (33 kJ/mol) into a nematic phase (N1) followed by a transition into another nematic phase (N2) at 70 °C (4.3 kJ/mol). The X-ray data of both phases are alike (see below). Upon cooling, no crystallization can be observed, either for 1a or 1d. However, for 1d an exotherm followed by an endotherm is

• kind of a nematic phase, in agreement with the optical textures. Obviously, similar clusters as in the isotropic phase are observed in the nematic phase. No changes of the X-ray pattern indicating a phase transition could be detected on heating above or on cooling below 70 °C (see Figure S1 in

Triphenylene discotic liquid crystal trimers synthesized by Co₂(CO)₈-catalyzed terminal alkyne [2 + 2 + 2] cycloaddition

• Bin Han,
• Ping Hu,
• Bi-Qin Wang,
• Carl Redshaw and
• Ke-Qing Zhao

Beilstein J. Org. Chem. 2013, 9, 2852–2861, doi:10.3762/bjoc.9.321

• mesomorphism. Keywords: Co2(CO)8 catalyzed cycloaddition; columnar mesophase; discotic liquid crystal; triphenylene; oligomer; Introduction Discotic liquid crystals (DLCs) with nematic phase have been commercially utilized in the liquid crystal display industry as optical compensating films for widening the

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

• for the difference in molecule structure), possess the nematic phase. The tilted smectic phase (SmC) being partially monotropic in character (i.e., the high temperature part of the phase is enantiotropic) has been observed on cooling below the nematic phase. For TL4, the temperature of the Iso–N phase

• within quite a broad temperature range. In Figure 1 microphotographs of textures for TL1 taken under different temperature and alignment conditions are presented, namely the marbled texture of the nematic phase obtained at 110 °C on a planar cell (Figure 1a), the schlieren texture of the nematic phase

• been determined by the characteristic platelet texture (similar to that presented in [29]) observed on planar samples by POM. Chiral TL5 with an azo group in the molecule core possesses the chiral nematic phase and the tilted ferroelectric smectic C* phase. Ferroelectric electro-optic switching has

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

• characterization is consistent with data from elemental and spectroscopic analysis. The materials thermal behaviour and phase characterization have been investigated by differential scanning calorimetry and polarizing microscopy. All the compounds exhibit a wide-ranging monotropic nematic phase. Keywords: bent

• -core mesogens; cyanobiphenyl; dipole moment; liquid crystals; nematic phase; polarity; Introduction Following the discovery of chiral and polar properties of mesomorphic bent-core compounds [1][2][3][4][5][6] the area of design, synthesis and properties of banana or bent-shaped liquid crystals (LC

• -ring systems and exhibit the so-called banana phases. However, there are relatively few examples reported in the literature based on bent-core compounds exhibiting a nematic phase [6][19][20][21][22][23][24] and in particular with possible ferroelectric switching [25][26] and a biaxial nematic phase

Formation of smectic phases in binary liquid crystal mixtures with a huge length ratio

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

Beilstein J. Org. Chem. 2012, 8, 1118–1125, doi:10.3762/bjoc.8.124

• revealed a destabilization of the nematic phase, which is present in the pure short compound, while the smectic state was stabilized. The short compound forms smectic A and smectic C phases, whereas the longer compound forms a broad smectic C phase and a narrow higher-ordered smectic phase. Nevertheless

• these studies, chemically similar mesogens with length ratios ranging from 1 to 1.8 were investigated. In the systems with a large difference in length, strong changes in the phase diagram were observed. The nematic phase was destabilized while the smectic state was stabilized. The temperature range of

• , with a length ratio of 1.8 [1][2]. Again, no destabilization of the smectic state was observed, and a eutectic point at approximately x16 = 0.015 was observed. However, the nematic phase disappears rapidly with increasing mole fraction x16 after a slight stabilization until x16 = 0.1, and it disappears

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

• the much higher nematic phase stability of CB-Ox-CB/3 compared to the higher homologue may be the result of decreased chain decoupling of the mesogenic units by the shorter spacers and the fact that the spacers are even numbered (considering the ether oxygens and the COO groups as parts of the spacers

• sufficiently long aliphatic segments and also the electrostatic interaction between the terminal CN groups and the aromatics seem to be responsible for the absence of any smectic phase and the complete mixing of the aromatics in the nematic phase. The low intensity of the diffuse small-angle scattering, due to

• )3COO) has much higher temperatures of the CybA–N and N–Iso transitions. Upon cooling a sample of CB-Ox/4 from the isotropic liquid, the nematic phase forms with a typical highly birefringent Schlieren texture (Figure 2b) [68]. This indicates a predominately homogeneous alignment (director n on average

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

• ; 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

• at ~101 °C and 107 °C, respectively. The conversion of the nematic phase to the isotropic phase in the case of 8b was observed at 117 °C. Similar investigations on phase transitions of compound 10b revealed that this material melts into a SmC phase at a much higher temperature, i.e., ~94 °C, compared

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

• nematic phase. Quite similar textures were published by Dierking [40][41]. The areas without birefringence in Figure 3 and Figure 4 derive from homeotropic alignment of the molecules. X-ray diffraction studies The assignment of the nematic mesophases were exemplarily confirmed by wide-angle X-ray

• scattering (WAXS) experiments on compound 11a. Representative 2D diffractograms of the crystalline phase, the isotropic phase and the nematic phase are shown in Figure 5. In the isotropic phase (Figure 5, part B) only a diffuse symmetric halo is observed. The diffraction pattern of 11a at 15 °C (Figure 5

• patterns of 11a: (A) crystalline phase at 50 °C, (B) isotropic phase at 25 °C, and (C) nematic phase at 15 °C. Diketonato metallomesogens and diketones with mesomorphic properties. Malonates and cyanoacetates tethered to calamitic 4-cyanobiphenyl units. Synthesis of malonate and cyanoacetates tethered to 4

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

• , based on the shape and chemical characteristics of the mesogen under investigation. The simplest is the nematic phase, whereby the mesogenic moieties exhibit an average alignment along a common direction (or director), whereas the smectic phases also display a degree of positional ordering (i.e., the

• moiety (612, Figure 4b) [61]. The thiol ligand exhibited a nematic phase, and the hybrids displayed a mesophase between 110 °C and 130 °C, but no distinct texture could be observed with POM (Table 1). Interestingly, direct observation of the possible arrangement of the NPs was obtained through annealing

• -mesogenic ligands: Side-on attachment The first assignment of a nematic phase for a pseudospherical NP was realised through the use of a laterally substituted rodlike mesogenic thiol (12, Figure 13) [69]. In this study, Au-NPs of diameters 1.6 ± 0.4 nm were targeted because of their small size and low

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

• [31]. Chirality parameter Q, calculated for compounds 1 and 2 by averaging over conformers. Conformer geometry and probabilities obtained by DFT calculations were used, unless otherwise specified. In the last column the HTPs measured in the nematic phase E7 are reported. Acknowledgements The authors

Laterally substituted symmetric and nonsymmetric salicylideneimine-based bent-core mesogens

• Sonja Findeisen-Tandel,
• Wolfgang Weissflog,
• Ute Baumeister,
• Gerhard Pelzl,
• H. N. Shreenivasa Murthy and
• Channabasaveshwar V. Yelamaggad

Beilstein J. Org. Chem. 2012, 8, 129–154, doi:10.3762/bjoc.8.15

• and OH 4b and 4d are new materials. As seen from Table 4, the nature of the mesophase changes upon introduction of the hydroxy groups, from a crystal-like BX phase to a SmCP phase (H 4c to OH 4c) and from a nematic phase to an undulated SmCP phase (H 4b to OH 4b). In the case of the 5-methoxy

• nematic phase is observed, which is very surprising for this mesogen having a molecular shape characteristic of banana-shaped liquid crystals. Although both legs of the bent-core molecules are extended by the C=C units, the clearing temperatures increase only by about 10 K. Introduction of a lateral

• methyl group on the central phenyl ring drastically decreases the melting temperatures. Therefore, broad SmCP phase ranges exist for OH 6b and OH 6c in comparison to the laterally unsubstituted derivative OH 6a. That also means that the nematic phase of H 6b changes to a polar smectic phase in OH 6b by

Symmetry breaking and structure of a mixture of nematic liquid crystals and anisotropic nanoparticles

• Marjan Krasna,
• Matej Cvetko and
• Milan Ambrožič

Beilstein J. Org. Chem. 2010, 6, No. 74, doi:10.3762/bjoc.6.74

• nematic configuration represents the simplest liquid crystal phase [6]. In the bulk nematic phase LC molecules tend to be oriented homogeneously along a single symmetry breaking direction. At the mesoscopic level the average local orientational ordering is commonly described by the nematic director field

• . The directions ± of this unit vector field are physically equivalent, reflecting the so called head-to tail invariance of LC phase on the mesoscopic scale. If ensembles are suddenly quenched from the isotropic to the lower symmetry nematic phase, then unavoidably a domain pattern forms [7]. The reason

• interaction energy with respect to all the spins. Therefore, we neglect thermal fluctuations. Consequently, our approach is sensible, deep in the nematic LC phase region, i.e. well below the isotropic–nematic phase transition. In order to satisfy the normalization of the spin vectors, = 1, the “operational

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

• columnar stacks in dodecane and at a certain concentration these stacks behave as molecules in a calamitic nematic phase, aligning accordingly. In reference [19] it is reported that aggregation of the discotic molecules already starts when they are in solution. This assembly can remain or influence the

Competition between local disordering and global ordering fields in nematic liquid crystals

• Matej Cvetko,
• Milan Ambrožič and
• Samo Kralj

Beilstein J. Org. Chem. 2010, 6, No. 2, doi:10.3762/bjoc.6.2

• ]. Studies so far have mainly focused on structural and phase behavior [8][9][10][11][12][13][14][15][16][17][18]. It has been shown that the isotropic nematic phase transition is typically replaced by the paranematic–nematic (PN–N) phase transition. The transition temperature in most cases decreases with

• increased disorder strength. If disorder is strong enough the transition can disappear. In the nematic phase memory effects can be observed revealing to some extent glass-like features. To our knowledge none of the studies so far have systematically explored the effect of external ordering field (B) in such

• deep in the nematic phase. The structure of the article is as follows. First we present the semi-microscopic lattice model that we use. Then the results are presented and discussed. In the following section we summarize our results. Some numerical details are summarized in the last section. Model We

Ring-alkyl connecting group effect on mesogenic properties of p-carborane derivatives and their hydrocarbon analogues

• Aleksandra Jankowiak,
• Piotr Kaszynski,
• William R. Tilford,
• Kiminori Ohta,
• Adam Januszko,
• Takashi Nagamine and
• Yasuyuki Endo

Beilstein J. Org. Chem. 2009, 5, No. 83, doi:10.3762/bjoc.5.83

• stabilization of the nematic phase, upon CH2→O replacement, was observed in p-carborane mesogens relative to benzene analogues. Thus, in series 1–4, the nematic phase is stabilized by about 14 K more for the pairs 1A/2A and 3A/4A, than for terphenyl (D) and bicyclo[2.2.2]octane (C) analogues (Figure 2

• to analyze the effect of the replacement of an alkoxy in 14[6] with an ester group in 15[6]. The CH2O→OOC exchange dramatically destabilized the nematic phase for the 10- and 12-vertex p-carborane derivatives, while a much smaller effect was observed for the carbocycles [25]. Series 14 and 15 [25

• exclusively the nematic phase. Similar nematic behavior is observed for carbocycles in series 17–20 with the exception of 19D, which exhibits a SmA phase in addition to a N phase. In contrast, most carbocyclic derivatives in series 14[6]–16[6] display only smectic and soft crystalline polymorphs. The bicyclo

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

• temperature range nematic. For the optimised mesogen structure, optical investigations by conoscopy monitored a uniaxial nematic phase upon cooling from the isotropic phase to room temperature (ΔT = 150 °C). X-ray studies on magnetic-field-aligned samples of this mesogen family revealed a general pattern

• 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

• ellipsoid spanned by three different semi-principal axes, possessing two different circular cross sections and consequently two optical axes (Figure 1, right side). In a biaxial nematic phase three molecular axes align along individual directors resulting in a material with three different refractive

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 of chemically similar smectogenic mesogens strongly differing in molecular length were investigated. In these mixtures the nematic phase present in the pure short mesogen disappeared rapidly on the addition of the longer mesogen, while the smectic state was preserved. In the smectic state the

• . In a naive model we now consider the liquid crystalline phase behaviour of mixtures of two types of these hard spherocylinders, which exhibit the same diameter but their lengths are differing by a factor of two. In this naive model, the nematic phase is expected – due to the absence of translational

• molecules with chemically similar cores but with length ratios in the order of 2:1 led us to the following general results: When the short-length compound exhibits a nematic phase, the nematic phase disappears quickly with increasing mole fraction of the compound with greater molecular length. Surprisingly

Coaxial electrospinning of liquid crystal-containing poly(vinylpyrrolidone) microfibres

• Eva Enz,
• Ute Baumeister and
• Jan Lagerwall

Beilstein J. Org. Chem. 2009, 5, No. 58, doi:10.3762/bjoc.5.58

• along the fibre axis in contrast to our experimental results. Possible explanations of this discrepancy might be either that the significant stretching during the electrospinning process leads to a shear induced phase transition to the nematic phase, causing a rearrangement of the molecules, or that the

Functional properties of metallomesogens modulated by molecular and supramolecular exotic arrangements

• Alessandra Crispini,
• Mauro Ghedini and
• Daniela Pucci

Beilstein J. Org. Chem. 2009, 5, No. 54, doi:10.3762/bjoc.5.54

• the ancillary ligand. Indeed a transition from a calamitic to a columnar mesophase is observed, through a calamitic/discotic cross-over point, due to the peculiar combination of two different molecular architectures. The mononuclear tropolonate derivative (A in Figure 2) shows a chiral nematic phase

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

• Abstract The addition of a chiral non-racemic dopant to a nematic liquid crystal (LC) has the effect of transferring the molecular chirality to the phase organization and a chiral nematic phase is formed. This molecular chirality amplification in the LC provides a unique possibility for investigating the

Progress in liquid crystal chemistry

• Sabine Laschat

Beilstein J. Org. Chem. 2009, 5, No. 48, doi:10.3762/bjoc.5.48

• smectic phases, nematic phase engineering by using V-shaped molecules, saddle-shaped columnar systems displaying anomalous odd-even effects, theoretical studies on the origin of chirality transfer in liquid crystalline host-guest systems, liquid crystalline carboranes and dyes and discotic phenanthrene

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

• peripheral flexible side groups that point outward [13][14][15][16]. They can be used for a variety of different optic and electronic applications, for example as materials for photovoltaics (in the columnar phase) [17][18][19] or as compensation layers in display technology (in the nematic phase) [20][21

• 1 with longer adaptable side groups are yet not investigated. Two compounds of that structure are described in this work. Macrocycle 26a melts isotropically at 98 °C (first heating, ΔH = 85.2 kJ/mol). However, cooling of the isotropic melt leads to the formation of a (monotropic) nematic phase at 90