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Abstract

The synthesis of 13 discotic mesogens is described in which the well-known hexakis(pentyloxy)triphenylene liquid crystalline material has been chemically modified to incorporate one, two, three and six carbazole moieties. These modifications have been achieved by the alkylation or esterification of mono-, di-, tri-and hexa-hydroxytriphenylene derivatives with alkyl bromides and carboxylic acids incorporating the carbazole moiety. The pure compounds are not liquid crystalline in nature but when doped with TNF, hexagonal columnar mesophases are induced, as shown by DSC, OPM and X-ray diffraction. These mesophases exist below room temperature. The mesophase clearing temperatures are dependent on several factors including the chain length separating the carbazole moiety from the triphenylene core, and the nature of the ether or ester linkage, and the degree of TNF doping. The data suggest that the most stable mesophases (highest clearing temperatures) are formed when a 2 : 1 complex is formed between the carbazole derivatives and the TNF, respectively. The correlation length obtained from X-ray diffraction reveals that the columnar order for one of the ether derivatives decreases, whereas the correlation length increases for one of the ester derivatives. This result suggests that the TNF is not only partaking in p-p noncovalent bonding interactions, but also in polar interactions with the CLO bond. Such mesogenic carbazole derivatives may have advantageous photorefractive properties over the amorphous polymeric materials.

About Supramolecular Assemblies of π-Conjugated Systems

“…It was shown that the resulting molecules did not possess liquid-crystalline behavior but could form hexagonal columnar mesophases of various stability, induced by TNF doping. 519 However, this occurred only when the carbazole substitution did not exceed two, indicating that the higher substituted compounds do not display ordered stacking behavior.…”

New Triphenylene Based Discotic Liquid Crystals with Mixed Tails: Molecular Symmetry and Wide Columnar Mesophase Range

“…It was reported that the 1∶1 mixture of electron-rich and electron-poor discogens displayed wider mesophase ranges and higher ordered columnar mesophases than the components. [24][25][26][27][28] Figure 2 showed POM texture photographs of columnar mesophases of the prepared triphenylene discogens. Those are typical fan-shaped textures of columnar mesophases.…”

“…In triphenylene based material design, peripheral sulfur atom promoted molecular self assembly, 11 hydrophilic and hydrophobic effect, 12 fluorophilic effect of perfluoroalkyl chain, [13][14][15] hydrogen bonding, 16 asymmetrical substitution, [17][18][19][20][21][22][23] electronic donor acceptor interaction, 24,25 complimentary polytopic interaction, 26,27 and arene perfluoroarene interaction 28 have been exploited for improving mesophase range, order of mesophase, and alignment behavior of discogens.…”

A discotic triphenylene dimer as organic hole transporting material for electroluminescence devices

“…3,6,7,10,11-pentahexyloxy-2-hydroxy-triphenylene 1 was prepared according to literature [9]. 2 is easily obtained by reacting 1 with excess amount of 3-bromopropanol.…”