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

• thermal and optical methods. Results demonstrated that mesophase stability in the series containing A–D follows the order (Alk)CH2CH2– < (Alk)OOC– < (Alk)CH2O– < (Alk)COO–. Surprisingly, the connecting groups (Alk)CH2CH2– and (Alk)OOC– destabilize the mesophase significantly stronger for carboranes (A and

• fluorination [18][19] on mesophase stability, and also the effectiveness of shielding of a lateral substituent [8][16][20] and chirality transfer phenomena [17]. Results of these studies are important for the design of new materials and optimizing of their properties for applications. During our investigation

• ). Similarly high values for phase stabilization of about 34 K are observed in pairs of alkyl and alkoxy dioxane derivatives 5[n] and 6[n] [4], as compared to similar benzene mesogens [24]. Also in series 7–11 the introduction of the connecting oxygen atom gives a larger increase in mesophase stability by an

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

• possess lower melting and higher clearing temperatures compared to their symmetric counterparts with the same number of methylene groups (compare 1b/2b and 1d/2f). It appears that a large difference in chain lengths results in higher stability of the mesophase, i.e. a low crystallisation tendency (see 2f

• previously reported two-step procedure. These mesogens are capable of hydrogen bonding if the esters are cleaved. The mesophase range and the melting temperature reach an optimum when the nematogens are desymmetrised with a butoxy and a heptyloxy spacer. For this molecule, optical observations by conoscopy

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

• confirmed by XRD experiments (see the Supporting Information). It should be noted that the allyloxy-substituted byproduct 9 showed a smectic mesophase between 50 °C and 67 °C as well. In contrast, the corresponding 4-allyloxy-4′-octylbiphenyl 11 showed only isotropic melting at 92 °C. The DSC results of

• chlorides 4 are summarized in Table 2. All members 4a–e showed enantiotropic SmA phases. For compounds 4a,c,e with even numbered spacer lengths smaller mesophase widths were observed as compared to compounds 4b,d with odd numbered spacer lengths. Furthermore an odd–even effect of both melting and clearing

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

• )sulfonyl]amide), are ionic liquid compounds without any supramolecular organization into mesophase. This is also the case in the series of compounds 5n with n < 12 (only a monotropic mesophase was observed for 512), and finally for 38. Supramolecular arrangement Despite the significant tendency of these

• the anion species and the general order is Br− > BF4− ≈ SCN− > PF6− > CF3SO3−. Dilatometric studies Prior to the analysis of the molecular packing of the various compounds in the smectic mesophase, the molecular volume (Vmol) of one salt, 112, was measured by using a home built high precision

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

• ]. In order to explore whether this anomalous odd-even effect is a more general phenomenon, the corresponding gallic ester-substituted tetraphenylenes were prepared and their liquid crystalline properties were investigated. In addition, we were curious about the mesophase types, because tetraphenylenes

• ,f additional crystal to crystal transitions were detected. A typical DSC curve is shown in Figure 1. Thus tetraphenylene 2h with dodecyl chains displays a melting transition at 3 °C and a clearing transition at 36 °C upon second heating. Upon cooling an isotropic to mesophase transition at 33 °C and

• chain derivatives 2j–l (n = 14–16) (shown for 2j in Figure S2 in the Supporting Information). Indeed, as expected the columnar mesophase seems to accommodate the eight bulky gallic esters much better than the smectic layer structure. The crossover from rectangular columnar to hexagonal columnar

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

• derivative [45] allowing the onset, even at room temperature, of a rectangular columnar mesophase which is stable over a very large temperature range (140 °C). The emission properties observed in the solution are preserved in the liquid crystalline state, therefore the flat disk-like molecular structure

• 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

• introducing of further aromatic rings equipped with several aliphatic tails each. Hence the synthesis of a series of cis-dichloro hexacatenar Zn(II) complexes has been performed (Figure 5) [56]. In this case the molecular organization in the mesophase, mainly driven by intermolecular attractive interactions

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

• properties such as ferroelectric or anti-ferroelectric switching [1][2][3][4][5][6][7]. The occurrence of superstructural chirality in the mesophase of bent-core compounds with no inherent chirality is not only of fundamental scientific interest but also of industrial application as this chirality can be

• , smectic and columnar phases. On the other hand, the unique geometry of the columnar mesophase formed by discotic liquid crystals is of great importance not only as models for the study of one-dimensional charge and energy migration in organized systems but also as functional materials for device

• mesophase. The transition temperatures and their associated enthalpies of the novel compounds are listed in Table 1. The symmetric dimer 6 melts at 51.1 °C on heating and crystallizes at 38.7 °C on cooling. Under polarizing optical microscopy we do not see any other transition, which was confirmed by

Synthesis of mesogenic phthalocyanine-C₆₀ donor–acceptor dyads designed for molecular heterojunction photovoltaic devices

• Yves Henri Geerts,
• Olivier Debever,
• Claire Amato and
• Sergey Sergeyev

Beilstein J. Org. Chem. 2009, 5, No. 49, doi:10.3762/bjoc.5.49

• ] in perfect agreement with POM observation. The small enthalpy value supports the transition from LC mesophase to isotropic liquid. However, assignment of the nature of LC mesophases for 1c,d from the available data was not obvious, since the textures observed by POM were not characteristic. The major

• comparatively high yields (up to 24%) for this type of reaction. Upon the favorable combination of the length of the linker with the length of peripheral substituents on the phthalocyanine, bulky C60 moiety can be accommodated in the LC mesophase. Detailed analysis of this supramolecular organization, as well

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

• of the compound. The term adaptable means that the orientation of substituents at that position can be influenced by an external parameter [25][26]. Compound 1 melts at 134 °C to form a nematic mesophase that becomes isotropic at 159 °C. However, compared to all previously reported discotic LCs, this

• solid state could help in understanding the absence of a mesophase, attempts were undertaken to perform a single crystal x-ray investigation on at least one of the compounds. By slow evaporation of a CH2Cl2 solution of 9a single crystals suitable for x-ray analysis could be obtained. 9a crystallizes as

• are also not bulky enough to extend into the interior of neighbored rings. Therefore, a physical crosslinking of the molecules, as it was supposed to be responsible for the absence of a mesophase in other shape-persistent rings, can be excluded. However, different to the previously investigated