Charge carrier transport in perylene-based and pyrene-based columnar liquid crystals

• Alessandro L. Alves,
• Simone V. Bernardino,
• Carlos H. Stadtlober,
• Edivandro Girotto,
• Giliandro Farias,
• Rodney M. do Nascimento,
• Sergio F. Curcio,
• Thiago Cazati,
• Marta E. R. Dotto,
• Juliana Eccher,
• Leonardo N. Furini,
• Hugo Gallardo,
• Harald Bock and
• Ivan H. Bechtold

Beilstein J. Org. Chem. 2023, 19, 1755–1765, doi:10.3762/bjoc.19.128

• understanding charge transport in columnar mesophases [9][10][11][12][13][14]. High charge carrier mobilities of 1.1 cm2 V−1 s−1 for p-type and up to 6.0 cm2 V−1 s−1 for n-type liquid-crystalline semiconductors have already been reported [15]. Among the various discotic liquid crystal materials, perylene

• observed mesophases. Compound 1 presents a wide range columnar hexagonal phase (Colhex) preserved at room temperature by cooling from the isotropic. Compound 2 shows an additional columnar rectangular phase (Colrect) below the Colhex and crystallizes under 166 °C. The HOMO and LUMO energy levels are also

• 1758 cm−1 (C=O). X-ray diffraction (XRD) measurements of 1 and 2 are shown in Figure 2. The Miller indices indicate the Colhex and Colrect character of the mesophases [31]. Despite crystallization of 2, the Colrect order is partially preserved at room temperature. The Colhex lattice parameter (a

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

• exhibit mesomorphic behaviour. In contrast, mesophases were observed for components employing NO2-Cn with longer alkyl chains. NO2-C10 showed focal-conic textures at 94 °C during cooling (see Figure 2a) and NO2-C11 showed an enantiotropic smectic behaviour (see Supporting Information File 1, Figures S11

• and S15). In our initial set of assemblies, we combined F4St with NO2-Cn with varying alkoxy-chain lengths (n = 8, 9, 10 and 11). The halogen-bonded assemblies exhibited mesogenic behaviour starting with an alkoxy chain length of n = 8. POM investigations revealed nematic mesophases for all complexes

• induces the formation of nematic mesophases with broad temperature ranges, the temperature range of the mesophase of the azobenzene-based assemblies is significant narrower. Theoretical calculations and the modular use of halogen bond donors with changing fluorination degree reveal that at least three

The use of isoxazoline and isoxazole scaffolding in the design of novel thiourea and amide liquid-crystalline compounds

• Itamar L. Gonçalves,
• Rafaela R. da Rosa,
• Vera L. Eifler-Lima and
• Aloir A. Merlo

Beilstein J. Org. Chem. 2020, 16, 175–184, doi:10.3762/bjoc.16.20

• , mainly due to their structural and electronic features. Isoxazoline and isoxazole cores show strong dipole moments, polarizabilities, anisotropic interactions and geometrical aspects that favor the formation of stable smectic A and nematic mesophases, respectively [19][20]. This work aimed at

• behavior [25][26] by segregation effects. Interestingly, isoxazoline 17a presented a monotropic SmA mesophase, while its regioisomer 17c did not show a mesophase. Corresponding isoxazoles formed stable mesophases as expected (N for 18a; SmA and N for 18c) [20]. Figure 1 shows the selected textures of the

• analogous compounds such as thiourea 18a,b, containing an isoxazole ring, displayed enantiotropic SmA and N mesophases, confirming that the isoxazole ring favors the formation of a stable mesophase. It is interesting to notice that the nematic mesophase appeared only in compounds with the isoxazole ring

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

• compounds 2 and 4 is constituted by a rigid core (three aromatic rings) to which are attached the terminal chains. Based on this structure, some liquid crystalline mesophases were expected. Differential scanning calorimetry (DSC), polarized optical microscopy (POM) and X-ray diffraction pattern analysis

• , compared to two-chain and shorter-chain homologues. Taking into account these observations, the inability of 2d to exhibit mesophases becomes axiomatic, since this compound is devoid of any terminal alkyl chain. X-ray patterns analysis In order to correlate the obtained results from POM and DSC, we have

Aggregation behaviour of amphiphilic cyclodextrins: the nucleation stage by atomistic molecular dynamics simulations

• Giuseppina Raffaini,
• Antonino Mazzaglia and
• Fabio Ganazzoli

Beilstein J. Org. Chem. 2015, 11, 2459–2473, doi:10.3762/bjoc.11.267

• concentration and on the solvent) and by their shape, which may preferentially determine stable mesophases, ranging from micelles to membranes, or even liquid crystals. It is well-known that the shape and the interactions among native or modified cyclodextrins can drive specific packing in the solid state, but

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

• immediately to an isotropic melt, but thermotropic mesophases are observed when the macrocycles have an appropriately substituted rim [29][30][31][32][33][34][35]. If the macrocycles pack on top of each other, hexagonal columnar or rectangular columnar phases can be observed in which the (empty) interior is

• able to accommodate small guest molecules [36][37][38][39]. In some cases, however, macrocycles with a filled interior seem to exhibit more stable mesophases compared to the compounds alike but with an empty interior [40]. Moreover, it has also been observed that even macrocycles with a flexible

• interior only, lacking the flexible rim, can form stable mesophases (macrocycles with an inverse structure) [41][42][43]. Recently, we presented a series of gel forming macrocycles that have an identical periphery but bear different intraannular substituents [11]. We were able to show that these

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

• formation of mesophases, and the introduction of a chiral lactate terminal chain destabilizes mesophases for the first type of mutual orientation of ester groups, attached to the central core. On the contrary, for the opposite orientation of esters, the terminal chain has no effect on the mesomorphic

• crystalline (LC) compounds have attracted broad interest in the past years due to their ability to form polar mesophases [1]. From the extensive studies, molecular structure–mesomorphic property correlation have been generalized and summarized in several reviews [2][3][4][5][6][7]. The structure of bent

• cyano end-capped bent-shaped materials it was documented [29][30][31] that reversing the position of hydroxylic and carboxylic groups exerts a profound effect on the mesophase properties. The bent-shaped molecules can create polar mesophases in spite of lack of molecular chirality. The most frequently

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

• view angles [1][2]. More interestingly, DLCs can self-organize into columnar mesophases with a high degree of order, and show fast unidirectional charge migration properties, and have been studied as soft organic semiconductors [3][4][5][6][7][8][9][10][11][12]. Solution-processed and ink-jet printing

• (Colro) and hexagonal columnar mesophases (Colho). Furthermore, the structure-mesomorphic property relationship is discussed. The synthetic route is shown in Scheme 1 and Scheme 2. Results and Discussion Synthesis and characterization We synthesized the key intermediate 1, 2-hydroxy-3,6,7,10,11-pentakis

• alkyne [2 + 2 + 2] cycloaddition reaction in moderate yields. Three of the four 1,2,4-trisubstituted benzene-cored discotic trimers have shown stable Colho and Colro mesophases and wide mesophase ranges including room temperature. The connecting linker group to the triphenylene and the spacer length to

Self-assembly of 2,3-dihydroxycholestane steroids into supramolecular organogels as a soft template for the in-situ generation of silicate nanomaterials

• Valeria C. Edelsztein,
• Andrea S. Mac Cormack,
• Matías Ciarlantini and
• Pablo H. Di Chenna

Beilstein J. Org. Chem. 2013, 9, 1826–1836, doi:10.3762/bjoc.9.213

• organogelators [22]. The steroidal LMOGs usually have substituents attached to the 3β-OH of the cholestane A ring and synthetic variations at the steroidal skeleton are scarce. Cholesterol-based LMOGs build mesophases in which steroid–steroid stacking is controlled by van der Waals forces. These interactions

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

• sulfonimide anion directly attached to the mesogenic unit. Keywords: anion exchange; ionic liquid crystals; ion pairs; mesophases; sulfonimides; Introduction While ionic liquids, i.e., molten salts composed of either organic cation or anion (or both) with melting points far below 100 °C, are extensively

• ). These patterns are typical for smectic mesophases and further confirm the assignment of a SmA phase based on POM observations. The exact layer spacing at each temperature was determined by fitting the first-order peak with a Gaussian distribution (Figure 3 and Supporting Information File 1, Table S1

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

• rarely nematic, columnar and cubic mesophases [4][5]. Combination of thermotropic and lyotropic properties for materials with definite molecular structure has been intensively studied so far [6][7][8][9][10][11][12][13][14][15][16] and is of high importance in particular for developing new types of

• functional LC materials [15][17][18]. Series of alkyl glucosides and related materials usually possess thermotropic mesophases [16] as well as lyotropic columnar phases in water solution [3]. The thermotropic SmA phase and hexatic/cubic/lamellar lyotropic phases have been detected for a series of 4

• , many open questions still remain. The objective of this work is to contribute to a better understanding of the chemical-structure–physical-property relationship for materials forming both, thermotropic and lyotropic mesophases. This understanding is of high potential interest for challenging issues

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

• ) has attracted considerable attention from different research groups in the past two decades. Bent-core compounds that exhibit mesomorphic properties were first reported by Vorlander [7][8] and later by Matsunaga et al. [9][10][11]. Later the mesophases were confirmed to be banana-type phases [12][13

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

• -1,3,4-thiadiazole unit is incorporated (Scheme 3). All compounds form nematic phases over wide temperature ranges, in some cases accompanied by additional nontilted (CybA) or tilted (SmC) mesophases at lower temperatures. Results and Discussion Synthesis and characterization The dimesogens and

• differential scanning calorimetry (DSC, DSC-7, Perkin-Elmer). The assignment of the mesophases is based on the combined results of optical textures and X-ray diffraction (XRD) studies. XRD investigations on aligned samples were performed by using a 2D wire detector (HI-Star, Siemens AG). Alignment was achieved

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

• introduce terminal chains, they can provide flexibility to stabilize the molecular alignment within the mesophase. Such terminal chains can either be nonpolar straight alkyl chains or carry a polar substituent. Such molecules may form both nematic and smectic mesophases depending upon the type of

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

• differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction (WAXS). Keywords: cyanoacetates; 4-cyanobiphenyls; liquid crystals; malonates; nematic; Introduction Nematic liquid crystals display mesophases in which the molecules are oriented along one vector defined by the director

• investigate the phase behaviour of metal β-diketonate complexes such as 1 [15] (Scheme 1). Although they were not able to detect any mesophases, their study motivated others to examine the mesomorphic properties of β-diketonates in more detail [16]. Among the first examples of a nematic β-diketonate is the Cu

• tautomers of ferrocenophanes have been previously studied by Galyametdinov [39]. In the first cooling runs the appearance of nematic mesophases was observed for both series 11a,b and 13a,b. All compounds displayed small transition enthalpies in a range between −0.3 and −0.7 kJ/mol (Table 1) for 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

• mesogens with essentially calamitic structures are arranged into layers). Columnar phases arise from the stacking of disclike mesogenic moieties into columns, which are in turn often arranged in a parallel manner into 2-D ordered lattices. Other mesophases include those possessing 3-D symmetry (cubic or

• particles to develop anisotropic shapes, which is crucial for their arrangement into liquid-crystalline phases (except cubic structures). Despite their apparently ideal shape characteristics, publications reporting on the thermotropic mesophases of suitably functionalised anisotropic NPs are relatively

• acicular particles. The mesophase behaviour was lost for hybrids prepared with 1 and NPs with lower aspect ratios and a deliberately prepared polydisperse sample, and furthermore, none of the hybrids prepared with the cyanobiphenyl based amine 2 exhibited any mesophases. In an extension of this work

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

• essentially determined by the axial chirality (helicity) of the core of the perylenequinones. Keywords: chirality; conformational analysis; DFT calculations; helical twisting power; nematic liquid crystals; Introduction The phenomenon of chiral induction in nematic mesophases has been known for a long time

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

• , Jalahalli, Bangalore 560 013, India 10.3762/bjoc.8.15 Abstract Bent-core mesogens have gained considerable importance due to their ability to form new mesophases with unusual properties. Relationships between the chemical structure of bent-core molecules and the type and physical properties of the formed

• mesophases are relatively unknown in detail and differ strongly from those known for calamitic liquid crystals. In this paper symmetric and nonsymmetric five-ring salicylideneaniline-based bent-core mesogens are presented, and the effect of lateral substituents attached at the outer phenyl rings (F, Cl, Br

• ) or the central phenyl ring (CH3) on the liquid-crystalline behaviour and on the physical properties is studied. Corresponding benzylideneaniline-based compounds were additionally prepared in order to study the influence of the intramolecular hydrogen bond. The occurring mesophases were investigated

Improved syntheses of high hole mobility phthalocyanines: A case of steric assistance in the cyclo-oligomerisation of phthalonitriles

• Daniel J. Tate,
• Rémi Anémian,
• Richard J. Bushby,
• Suwat Nanan,
• Stuart L. Warriner and
• and Benjamin J. Whitaker

Beilstein J. Org. Chem. 2012, 8, 120–128, doi:10.3762/bjoc.8.14

• low-angle X-ray diffraction. The DSC data is summarised in Table 2, the phase behaviour of the isoalkyl series is compared graphically with that for the n-alkyl series in Figure 1 and typical polarizing micrographs are shown in Figure 2. Compounds 7b and 7c exhibit Colh columnar mesophases. For

A surprising new route to 4-nitro-3-phenylisoxazole

• Henning Hopf,
• Aboul-fetouh E. Mourad and
• Peter G. Jones

Beilstein J. Org. Chem. 2010, 6, No. 68, doi:10.3762/bjoc.6.68

• and smetic mesophases associated with their rod-like core structure [9]. The pioneering work on furoxans as nitric oxide donors by Gasco et al. has stimulated a large number of further studies. One of these reports deals with a synthetic route and structural characterization of two isomeric

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

• the SmF phase in the latter. A DSC trace for 16D[6] is shown in Figure 3, and representative textures of its mesophases are presented in Figure 4. The tilted phases in both terphenyl compounds were identified by the appearance and subsequent characteristic changes of the Schlieren textures in the

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

• connected via alkyloxy spacers, was efficiently prepared by a two-step procedure. Phase engineering results in an optimum of the mesophase range and low melting temperature when the nematogens are desymmetrised with a butoxy and a heptyloxy spacer. The mesophases are enantiotropic and over the whole

• 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

• supercooled without crystallisation. Some materials can be stored for more than 1 h at 25 °C without visible formation of crystal grains. Microscopy studies were performed to examine the nature of the mesophases. POM revealed for all samples Schlieren textures with two and four brushed disclinations (Figure 5

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

• nucleophilic substitution. The mesomorphic behaviour of these compounds was investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (WAXS and SAXS) and revealed smectic A mesophases for bromides, chlorides and azides 3, 4 and 6. For these compounds a

• crystallization peak at 24 °C. The SmA to crystalline transition tends to strong supercooling in the order of 10–30 K (Table 1, Figure 1). POM observation of 3a–e revealed fan-shaped textures typical of SmA phases. An illustrative example is depicted in Figure 2. The assignment of the SmA mesophases was further

• derivative 6c is shown in Figure 5. POM revealed fan-shaped and focal conic texture, see for example Figure 6. Figure 7 and Figure 8 reveal that due to substantial supercooling for all spacer chain lengths and terminal groups the mesophases are smaller during the heating cycle as compared to the cooling

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

• molecules to form spontaneously a single homeotropic monodomain (Figure 5a) the nature of the mesophases could be quite easily assigned on the basis of their optical textures if separated microscope slides (100 μm spacer) were used. The utilization of a spacer allows the formation of large oriented

• identification of all mesophases was supported by small-angle X-ray diffraction. SAXS patterns were collected for the mesomorphic salts as a function of temperature (Figure 6). Typically, in all cases, in the large angle region, i.e. at ca. 4.5–4.6 Å, a very intense and diffuse scattering halo was observed

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

• not show any mesomorphic properties, whereas compounds 2e–i with C9–C13 chains displayed rectangular columnar mesophases and compounds 2j–l with C14–C16 chains displayed hexagonal columnar mesophases. Furthermore an anomalous odd-even effect of the clearing points of compounds 2e–l versus chain length

• was detected. Keywords: columnar mesophases; discotic liquid crystals; tetraphenylene; Introduction Columnar liquid crystals have received increasing interest during the last decade due to their 1D charge transport and self-healing properties, which make them particularly promising candidates for

• chemistry, asymmetric catalysis and formation of inclusion complexes [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. We have shown that tetraphenylenes with eight peripheral alkoxy or alkanoate chains display thermotropic columnar and smectic mesophases [29