Novel Annulated Triphenylene Discotic Liquid Crystals Generated by Pictet‐Spengler Cyclization

Abstract

Triphenylenes have been frontrunner in discotic liquid crystalline materials since their discovery. They possess great richness of mesomorphism in them. Chemists have been exploring this potential quite often by some substitutions in the core or periphery of the triphenylene molecule. In this current report, we extended the triphenylene ring system by fusing with nitrogen and studied their mesomorphic and optical properties. Four new compounds are prepared using Pictet‐Spengler cyclization of hexaalkoxytriphenylene‐1‐amine with various aldehydes. All the new compounds are well characterized using spectral and elemental analysis. Their mesomorphic properties are evaluated using polarizing optical microscopy, differential scanning calorimetry and X‐ray diffractometry. These derivatives showed columnar hexagonal phase with great promise for further studies.

Ambipolar Charge Transport Properties of Naphthophenanthridine Discotic Liquid Crystals

“…The synthetic pathway of the compounds is shown in Scheme ; the synthesis was carried out following the literature procedure. , 1,2-Dibutyloxybenzene 2 was synthesized from catechol and n -butyl bromide in the presence of potassium carbonate. The purified dibutyloxy benzene was oxidatively trimerized using ferric chloride through the Scholl reaction to form hexabutoxytriphenyene 3 , which was nitrated using 70% nitric acid (1 equiv) to get mononitro-hexabutyloxy-triphenylene 4 .…”

“…Thermotropic discotic liquid crystalline materials overcome this restriction through columnar organization, that is, the disc-shaped molecules stack on top of each other to form a one-dimensional column which further occupies various two-dimensional lattices. These mesogenic materials, which are known as one of the delicate phases of matter, exhibit both order and mobility, and the homogeneous domains can be achieved sometimes to a larger length scale which is essentially required for semiconducting devices. − The discovery of discotic liquid crystals by Chandrasekhar et al has motivated research groups around the globe to explore new discogens and study their charge transport character. − Discotic liquid crystals have been used in photoconductive devices due to their high charge carrier mobility. , Generally, the mesogenic stability of discotics and the charge transport property are influenced by the size of the π-conjugated core, the nature of substituents, and the relative positioning of the neighboring molecules. − Recently, nitrogen-containing polycyclic aromatic molecules have drawn enormous interest as n-type semiconductors because of their expanded electron affinity and enhanced π-stacking. − Many reports on nitrogen-fused discotic systems are known to be highly emissive for a broad wavelength range , and device applications. − Our group has previously reported various nitrogen-incorporated discotic systems through ring fusion and ring annulation for their liquid crystallinity and applications. − The charge transport properties of many different discotic derivatives and their nanocomposites have been reported in the literature. − The ambipolar charge transporting molecules are of special interest for organic semiconductors as they enable the fabrication of complementary circuits, OFETs, and OLEDs. − In addition, fine-tuning the energy levels of the HOMO and the LUMO by incorporating substituents may result in desirable charge transport properties . Generally, this type of bipolar transport has been achieved through bulk heterojunctions of donor and acceptor materials as active components , or by introducing different source and drain electrodes to facilitate the charge transport .…”

Charge Mobility in Discotic Liquid Crystals

“…In this subsection, the last developments regarding the synthesis of novel discotic mesogenic materials will be described. Triphenylene derivatives still remain the most studied compounds and they have been used to develop new materials, testing new side chains, or new cores [ 191 , 192 , 193 , 194 , 195 , 196 ], to be linked with other cores to prepare dyads and triads [ 67 , 197 , 198 , 199 , 200 ] or materials giving segregate columns [ 201 , 202 ]. Triphenylenes were also doped with nanoparticles or used to prepare blends with other mesogenic molecules [ 203 , 204 , 205 ].…”

Method of Molecular Parameters for Columnar Mesomorphism Prediction of Tristriazolotriazines

“…является актуальной областью исследований для более эффективного практического использования [1][2][3][4][5]. Если каламитные ЖК уже нашли достаточно широкое применение в современных нанотехнологиях, являясь, например, ключевыми элементами ЖКдисплеев [6][7][8], то использование дискотических мезогенов (ДМ) в этой области все еще находится на начальной стадии развития [9][10][11][12]. Большинство ДМ состоит из ароматического ядра, например, трифенилена, коронена, труксена, перилена и т.д., часто включая богатые электронами фрагменты по периферии центра, такие как алкоксибензолы, тиофены и др.…”

“…Большинство ДМ состоит из ароматического ядра, например, трифенилена, коронена, труксена, перилена и т.д., часто включая богатые электронами фрагменты по периферии центра, такие как алкоксибензолы, тиофены и др. [10,11,13]. В последние годы более активно исследуются мезогенные гетероциклические структуры с дефицитом электронов и фотолюминесценцией, такие как триазины, тристриазолотриазины, оксадиазолы, пиримидины и др.…”