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

• core, the obtained compounds do not exhibit mesomorphism, only crystal–isotropic transitions were observed [26]. The absence of mesophases is mainly due to the strong bend (134°) between the aromatic rings, which disturbs the linear shape of the whole molecule [27]. Herein we describe the synthesis and

• fundamental difference between fluoro- and hydrocarbon chains mentioned above. The conformation A adopted by these compounds (Figure 5a–a”) lowers the dipole moments and thereby precludes mesophases formation. In the same way, we can rationalize the absence of mesomorphism in compound 2c which is not only non

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

• ) polarization switching. The mesomorphic thermal stabilities of these compounds are discussed in the domain of the symmetry and the flexibility of the alkyloxy end chain length attached to the chiral center. Keywords: 3,5-disubstituted-1,2,4-oxadiazoles; ferroelectric switching; mesomorphism; optical textures

• -oxadiazole ring without effecting [35][36][37] the ester group (δC = 165.76 ppm), attached to the phenyl ring under these conditions. Phase characterization The mesomorphism exhibited by the compounds is characterized by a polarizing optical microscope (POM) equipped with a hot stage. The sample is

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

• oligomers. Mesomorphism POM and DSC Initially, we studied the mesomorphic properties of the monomers and trimers by using polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). The POM results of the monomers and trimers are summarized in Figure 1 and Figure 2, respectively. The

• DSC traces are shown in Figure 3 and the phase transition data are summarized in Table 1. For the mesomorphism of the functionalized triphenylene monomers, compound 2 [52] and 3b [57] have been reported, 3a and 3c are new. They all display typical optical textures with homeotropic alignment behavior

Synthesis of guanidinium–sulfonimide ion pairs: towards novel ionic liquid crystals

• Martin Butschies,
• Manuel M. Neidhardt,
• Markus Mansueto,
• Sabine Laschat and
• Stefan Tussetschläger

Beilstein J. Org. Chem. 2013, 9, 1093–1101, doi:10.3762/bjoc.9.121

• . Thus, the presence of mesogenic counterions could not overcome the known tendency of sulfonimides to inhibit mesomorphism. Experimental General Information. All reactions were carried out under a nitrogen atmosphere with Schlenk-type glassware and the solvents were dried and distilled under nitrogen

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

• molecular architectures [31][32][33][34][35][36][37][38][39]. Furthermore, the introduction of a polar cyanobiphenyl moiety in bent-core systems exhibiting mesomorphism is rare [22]. Design of the molecule The recent experimental support in favour of a biaxial nematic phase that is exhibited by bent-core

• substituent. The unsubstituted homologue 1d with a terminal n-octyloxy chain did not exhibit mesomorphism. Similarly, in cases where the chloro substituent was shifted to the 4-position, the compound 1e, with a n-hexyloxy terminal chain, or its higher homologue with a n-hexadecyloxy chain 1f, did not exhibit

• mesomorphism. It is surprising that the aspect ratio of all compounds is almost the same, but the compounds with a transverse chloro substituent exhibit monotropic nematic phases, while the other homologues with a lateral dipole did not exhibit mesomorphism. In general, the monotropic behaviour was often

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

• organic ligand coating and their resulting phase behaviour. Mechanisms proposed to explain the supramolecular organisation of the mesogens within the liquid-crystalline phases are discussed. Keywords: hybrid; liquid crystal; mesogen; mesomorphism; mesophase; nanoparticle; self-organisation; supramolecule

• presence of a solvent are known as lyotropic. A material that exhibits LC properties is referred to as a mesogen and is said to exhibit mesomorphism; although something that is mesogenic (e.g., proto-mesogens) is not necessarily mesomorphic. Thermotropic liquid crystals are usually formed by molecules that

• diameter coated with triphenylene based mesogenic thiols 236,6 (Figure 25) were prepared by using the direct method to give a surface exclusively coated with the discotic ligands [93]. These materials did not display mesomorphism in the neat state, but were readily dispersed into the columnar phase of

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

• ability to exhibit mesomorphism. Interest in such nonconventional mesogens increased remarkably in the mid-1990s following the report by Niori and co-workers [1] that the mesophases (banana phases) formed by 1,3-disubstituted benzenes hold unusual properties. As a result, a large number of banana-shaped

• linked to the central phenyl ring. The influence on the mesomorphism of a fluoro substituent at the central phenyl ring was studied by Rao et al. [43]. Three years ago, we reported the synthesis and a remarkable electro-optical behaviour of three bent-core compounds derived from 2-methyl-1,3

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

• mesomorphism in homologous series where nematic is the dominating mesophase for short-length homologues, SmA for medium-length homologues and SmC for longer homologues (see e.g. [1]). For all mixtures small angle X-ray scattering (SAXS) measurements were performed. Figure 4 shows the layer spacing in the SmA

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

• mesophase. We thus wondered whether variation of the spacer chain lengths and terminal group X (Scheme 2) might have significant influence on the mesomorphism. The results of this study are discussed below. Results and Discussion Syntheses: In order to obtain different series 3–7 the known 5-(4

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

• cation and containing anions varying with regard to their shapes, sizes and charge localization. As expected, most of the imidazolium compounds show stable mesomorphism, which can be observed at sub-ambient to very high temperature. Both the alkyl chain length and the anion type have a strong influence

Saddle-shaped tetraphenylenes with peripheral gallic esters displaying columnar mesophases

• Eugen Wuckert,
• Constanze Hägele,
• Frank Giesselmann,
• Angelika Baro and
• Sabine Laschat

Beilstein J. Org. Chem. 2009, 5, No. 57, doi:10.3762/bjoc.5.57

• -ray diffraction (WAXS, SAXS). The DSC results are summarized in Table 1. While compounds 2a–d with chain lengths up to C8 showed only crystal to crystal transitions and isotropic melting, tetraphenylenes 2e–l with chain lengths between C9 and C16 displayed enantiotropic mesomorphism. For compounds 2e

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

• that mesomorphism of the organic precursors is preserved after complexation [38]. More recently, our work has addressed the design of new, higher performing complexes, whose structures, inaccessible for organic liquid crystalline systems, are able both to induce very low transition temperatures and to

• -diketonate ligands, giving rise to a series of mononuclear complexes combining two chelating functional moieties in their structures (Figure 2) [49]. The coordination to the Pd(II) centre induces, in all the resulting compounds, thermotropic mesomorphism whose nature has been found to be strictly related to

• , containing as ancillary ligands some acetylacetonates, are “non conventional” shaped palladiomesogens. Indeed, they completely lack terminal tails, usually necessary for inducing mesomorphism. In this case the presence of fluorinated groups on the complementary ligands promotes a delicate balance between

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

• ends, the packing of the bent-cores in layers will not be favored. In other words, the bent core-bent core interactions are too weak to produce any B-phase. On the other hand, the two triphenylene units in compound 6 when attached with flexible methylene spacers exhibit columnar mesomorphism. However

• , in compound 6 they are attached to each other with a intervening rigid bent core unit which is probably not allowing the two discs to lie in the same plane and hence hinders columnar mesomorphism in this architecture. So non-coplanarity of the discs and the rigid bent-core unit in the spacer seems to

• . These polarizing optical microscopy observations are confirmed by differential scanning calorimetry measurements. The absence of mesomorphism in this architecture may arise from two competing factors. First, the bent core units will try to pack in layers by microsegregation but in this kind of packing

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

• )-4-iodobenzene using Cu(II)-NaY as catalyst and K2CO3 as base is reported. By this synthetic approach, mesomorphic 3-[4-(dodecyloxy)phenyl]-1-methyl-1H-imidazol-3-ium iodide was synthesized in a two-step procedure, and its mesomorphism has been fully investigated by polarised optical microscopy

• -arylation of imidazole as a means of expanding the aromatic core and obtaining unsymmetrical imidazolium liquid crystals (Scheme 1). We also describe the influence of the counter anion on the mesomorphism, electrochemistry and the UV properties of these imidazolium salts. Results and Discussion Synthesis

• properties and mesomorphism, we prepared compounds with BF4− (1b), PF6− (1c), CF3SO3− (1d) and (CF3SO2)2N− (1e) anions in excellent yield by anion metathesis in water/CH2Cl2 as solvent (Scheme 4). All these compounds were fully characterized by 1H NMR, 13C NMR {1H}, FT-IR and UV spectroscopy, as well as