A Novel Biaxial Smectic Liquid Crystalline Phase Formed by Rodlike Molecules with a 1,3-Diazaazulene Skeleton

Abstract

Novel rodlike liquid crystalline (LC) materials incorporating the nonbenzenoid aromatic 1,3-diazaazulene unit have been synthesized and investigated by polarizing microscopy, differential scanning calorimetry, and X-ray diffraction of oriented samples. Some representatives form, in addition to conventional SmC phases, a novel biaxial smectic LC phase, in which the rotation of the molecules around their long axes is greatly restricted. Attractive face-to-face interactions of the flat aromatic units lead to columnar aggregates which are organized in layers. As there is no positional correlation between adjacent layers, these mesophases are related to lamellar columnar phases formed by some disklike and boardlike molecules. Such LC materials may be promising candidates in the field of organic semiconductors, photoconduction, and other applications.

A Room‐Temperature Liquid‐Crystalline Phase with Crystalline π Stacks

“…This phase is different from those already reported for LC PDIs, which are either columnar,9, 12c, d smectic,12a,b or lamellar columnar phases 6. The phase is related to lamellar columnar phases6, 13 and can be considered as a more ordered version of a biaxial smectic phase 14. It is best described as a highly ordered columnar smectic phase, which typifies its long‐range lamellar order, with 2D‐crystalline in‐layer positional order including π stacking order.…”

Discotic Liquid Crystals: From Tailor‐Made Synthesis to Plastic Electronics

“…288 Only the octasubstituted board‐like mesogen 206 b forms columnar mesophases, while the tetrasubstituted analogue 206 a displays a soft crystal phase (Scheme ). A novel biaxial smectic liquid‐crystalline phase formed by the rodlike 1,3‐diazaazulene 207 was recently reported by Tschierske, Mori, and co‐workers (Scheme ) 289…”

Diskotische Flüssigkristalle: Von der maßgeschneiderten Synthese zur Kunststoffelektronik

“…[289] Da Tetrathiafulvalene besonders für organische Leiter brauchbare Materialien sind, wurden die Synthese und Eigenschaften dieser Verbindungsklasse intensiv erforscht. [290] Dennoch wurde erst 1998 das erste columnare Mesogen mit einem TTF-Kern beschrieben.…”