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

• (see also Figure 2b) which is in contrast to the behaviour of pristine NO2-Cn showing a smectic phase for the alkoxy chain lengths of n = 10 or 11. A strong odd–even effect was observed for the NO2-Cn∙∙∙F4St assemblies which indicates a significant impact of the alkyl chain length on the packing of the

Synthesis of organic liquid crystals containing selectively fluorinated cyclopropanes

• Zeguo Fang,
• Nawaf Al-Maharik,
• Peer Kirsch,
• Matthias Bremer,
• Alexandra M. Z. Slawin and
• David O’Hagan

Beilstein J. Org. Chem. 2020, 16, 674–680, doi:10.3762/bjoc.16.65

• phases. The smectic phase of LC 8 was maintained over a broad temperature range (54–84 °C), whereas that for 10 and 11a only showed a melting point and these compounds did not display any obvious liquid crystallinity (Table 1). Therefore, any development of these latter materials would require extended

Synthesis, liquid crystalline behaviour and structure–property relationships of 1,3-bis(5-substituted-1,3,4-oxadiazol-2-yl)benzenes

• Afef Mabrouki,
• Malek Fouzai,
• Armand Soldera,
• Abdelkader Kriaa and
• Ahmed Hedhli

Beilstein J. Org. Chem. 2020, 16, 149–158, doi:10.3762/bjoc.16.17

• , which generates a lamellar packing and thus contributes to smectic phase stability [14]. It was reported that even simple n-alkanes containing a fluorocarbon block produces smectic phases [15][16][17][18][19]. Some molecules having only a single aromatic ring and fluorinated tail show smectic phases

Mechanochemistry of nucleosides, nucleotides and related materials

• Olga Eguaogie,
• Joseph S. Vyle,
• Patrick F. Conlon,
• Manuela A. Gîlea and
• Yipei Liang

Beilstein J. Org. Chem. 2018, 14, 955–970, doi:10.3762/bjoc.14.81

• derivative (Figure 5) and its cytosine congener in an undefined "vibrator mill" at room temperature. However, above 80 °C a solid-state transition was observed in which base-pairing was inferred and upon further heating gave a smectic phase [82]. Using a mixer ball mill, Vogt and co-workers ground 5

• ) Crude solid ball mill click reaction mixture after removal from copper vessel (left) and during extraction of pure product with DMSO (right). Early low temperature mechanised ball mill as described by Mudd et al. – adapted from reference [78]. Materials used to prepare a smectic phase. Structures of 5

Novel biphenyl-substituted 1,2,4-oxadiazole ferroelectric liquid crystals: synthesis and characterization

• Mahabaleshwara Subrao,
• Dakshina Murthy Potukuchi,
• Girish Sharada Ramachandra,
• Poornima Bhagavath,
• Sangeetha G. Bhat and
• Srinivasulu Maddasani

Beilstein J. Org. Chem. 2015, 11, 233–241, doi:10.3762/bjoc.11.26

• simultaneous observation of threads and broken focal conic fan texture infers [39] that the LC phase is a tilted smectic phase. This texture is found to be similar to the texture reported [40] for the polar smectic-C (SmC*) phase of octyl 4-(4-(3-(4'-(undec-10-en-1-ylcarbonyloxy)biphenyl-4-carbonyloxy

Unusual polymorphism in new bent-shaped liquid crystals based on biphenyl as a central molecular core

• Anna Kovářová,
• Svatopluk Světlík,
• Václav Kozmík,
• Jiří Svoboda,
• Vladimíra Novotná,
• Damian Pociecha,
• Ewa Gorecka and
• Natalia Podoliak

Beilstein J. Org. Chem. 2014, 10, 794–807, doi:10.3762/bjoc.10.75

• experimental techniques and will be described in details later. Series I Compounds Ia and Ic exhibit the SmCAPA phase in a very narrow temperature interval on cooling only (in both materials the smectic phase is monotropic). Introduction of a perfluoroalkyl chain in material Ib has a pronounced effect on this

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

• of the glass plates are covered by indium-tin-oxide electrodes and polyimide layers unidirectionally rubbed, which ensures planar alignment of the molecules, e.g., bookshelf geometry in the smectic phase. In addition, for texture observation on samples with homeotropic alignment, free-standing films

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

• with respect to mesogenicity to exhibit an anticlinic bilayer smectic phase (SmAPA), and to its stability towards hydrolysis. The mesomorphic behaviour of compounds 1a–1c was characterized by polarized optical microscopy (POM), and the samples, on cooling from the isotropic phase, exhibited marble or

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

• as the system with a length ratio of 1.8, but also the first signs of reduced miscibility. The long compound used in this study, PhP16 (see below in Scheme 1 and Figure 2), exhibits a heretofore unidentified higher-ordered smectic phase [4], which we have identified by detailed investigations

• and a narrow higher-ordered smectic phase. Its molecular length was determined by molecular modelling as 50.6 Å. The component with short molecular length is the asymmetric compound 2-(4-butoxyphenyl)-5-octyloxypyrimidine (2PhP) [4]. It exhibits the typical liquid-crystalline phase sequence of nematic

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

• 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

• phase. The smectic phase was investigated by XRD of a surface-aligned sample. The 2D XRD profile (Figure 6a) has a sharp Bragg peak (d = 4.4 nm) with its second-order reflection located on the meridian, confirming a well-defined layer-like organization. In the wide-angle region there is a diffuse

• in principle be possible for both compounds, Thia-Ox/5 and Thia-Ox/10. It appears that the very different lengths of the two mesogenic units and probably also the bent shape of these units contribute additionally to destabilization of the smectic phase. Although these two thiadiazole-containing

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

• into the smectic phase through another shift of c/2, followed by positional decoupling of the layers along the c axis (Figure 9). Interestingly, the important role of the alkylthiol coligand (referred to as the “primary grafting layer”) in determining the LC behaviour of these swallow-tailed hybrids

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

• -phase behaviour SmA–SmAb–SmA was reported [28]. Rao et al. postulated a new chiral smectic phase formed by W-shaped achiral molecules that contain two salicylideneaniline units (Scheme 1B) [29][30]. Recently, new achiral four-ring molecules were reported by Deb et al., in which two substituted

• -frequency triangular wave voltage shown in Figure 3a gives evidence that the tilted smectic phase exhibits an antiferroelectric switching behaviour. Cooling the isotropic liquid in the presence of a D.C. field leads to the formation of circular domains, in which the layers are arranged cylindrically. In the

• phases the angle between the extinction crosses and the crossed polarisers corresponds to the tilt angle of the smectic phase. As shown in Figure 4b, circular domains appear under application of a sufficiently high electric field. After removal of the electric field, the relaxation of the field-induced

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

• . Demixing of the two kinds of mesogens occurs locally inside the layers. Furthermore the layer spacing of such a smectic phase would – for all mole fractions – correspond to the length of the longer molecule (Figure 11a). However, in our SAXS-measurements we observed a layer spacing which varied linearly

• smectic phase would correspond to the added lengths of the two molecules (Figure 11b). As the experimentally found layer spacing is always smaller than the long molecule, this also cannot be the correct explanation. The last possibility is a more dynamic picture, where the space is filled by out-of-layer

Influence of spacer chain lengths and polar terminal groups on the mesomorphic properties of tethered 5-phenylpyrimidines

• Gundula F. Starkulla,
• Elisabeth Kapatsina,
• Angelika Baro,
• Frank Giesselmann,
• Stefan Tussetschläger,
• Martin Kaller and
• Sabine Laschat

Beilstein J. Org. Chem. 2009, 5, No. 63, doi:10.3762/bjoc.5.63

• crystallization peak at 42 °C were observed. POM investigation displayed fan-shaped and focal conic textures, as exemplified in Figure 4. XRD experiments proved the smectic phase. In contrast to the bromides 3 and chlorides 4, the hydroxy and azide derivatives 5a,b and 7b–e were non mesomorphic and showed only

1-(4-Alkyloxybenzyl)-3-methyl-1H-imidazol-3-ium organic backbone: A versatile smectogenic moiety

• William Dobbs,
• Laurent Douce and
• Benoît Heinrich

Beilstein J. Org. Chem. 2009, 5, No. 62, doi:10.3762/bjoc.5.62

• observed as a black isotropic texture under POM, (b) focal conic texture observed at 80 °C with 18 (spacer Mylar foil 100 μm). Diffraction small-angle X-ray pattern of the smectic phase of 212 recorded at T = 100 °C. Variation with the counter-ion of the molecular area S and of the ionic sublayer thickness

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

• (vinylpyrrolidone) with the liquid crystal 4-cyano-4′-octylbiphenyl in its smectic phase as core material could be produced. The encapsulation leads to remarkable confinement effects on the liquid crystal, inducing changes in its phase sequence. We conducted a series of experiments to determine the effect of

• unexpected when considering the viscosity anisotropy of the liquid crystal kept in its smectic phase during electrospinning. Keywords: coaxial electrospinning; composite material; core-sheath fibres; liquid crystal; smectic phase; Introduction Electrospinning is a versatile process for producing nano- and

• PVP as sheath and the liquid crystal 4-cyano-4′-octylbiphenyl (8CB) as core produced by coaxial electrospinning. The latter LC exhibits a smectic phase (phase sequence: cryst. 20.5 SmA 32.0 N 39.2 iso.) in contrast to the LC used in our previous work, which formed only a nematic liquid crystal phase

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

• . more than twice d001), the difference in molecular volume (smectic phase: Vmol = 622 Å3 at 20 °C; crystalline phase: Vmol = V/2 = 577 Å3) just coincides with the contribution of the chain melting [25][26], indicating that the partial volume of the ionic sublayer does not change significantly between

• being the chain volume) simultaneously expands in proportion (from 9.5 Å in the crystalline phase to 20 Å in the smectic phase at 20 °C). These lateral shrinkage and longitudinal extension events are the result of a ruffling process of the ionic sublayers, starting from the completely flat state in the

• smectic molecular organisations. In the crystalline phase, the ionic sublayers just impose their area and the tails tilt until dense packing is reached. In the smectic phase, tail tilting is not favourable upon the amphipathic expelling at the interface with the ionic sublayer and the system adopts a