Advances in Metal‐Free Heterocycle‐Based Columnar Liquid Crystals

Abstract

Liquid crystals are ordered soft materials formed by self-organized molecules and can potentially be used as new functional materials for electron-, ion- or molecular-transport; optical; and bio-active materials. In particular, the columnar liquid crystals are promising candidates used in various optical and electronic devices. For this purpose, design and synthesis of unconventional materials are essential. In this review, we have summarized several approaches for the synthesis of columnar liquid crystals composed of various heterocyclic systems. We also outline their liquid crystalline and other relevant properties, and their suitability for applications in diverse fields.

Hexacatenars Exhibiting π-π Driven Supergelation, Aggregation Induced Blue Light Emission and Thermochromism

“…The scarcity of blue emitters is due to the requirement of high band gap and instability . Introduction of heterocyclic units in the molecular structure of mesogens greatly contributed in the design of luminescent LCs . Among heterocyclic units, the compounds based on 2,5‐diphenyl‐1,3,4‐oxadiazole units are particularly found importance in OLED fabrication due to their high thermal stability, electron transporting and/or hole blocking nature, blue luminescence and high quantum yield .…”

Supramolecular Columnar Liquid Crystals Formed by Hydrogen Bonding between a Clicked Star‐Shaped s‐Triazine and Benzoic Acids

“…One approacht oo btain supramolecular columnar liquid crystalsi sb yh ydrogen-bonding of ah eterocyclic core that does not show the columnar phase with complementary peripheral units, such as some readily accessible promesogenic carboxylic acids. [3] There are only af ew examples of systems that have been produced by following this method, [4] although it is an interesting and useful strategy to access novel functional columnar nanostructures when a p-conjugated core is used. [5] Therefore, to obtain novel supramolecular columnar liquid crystalsbyinteraction with carboxylic acids, novel discot-ic building blocks that are able to interactt hrough hydrogen bondinga re necessary.I nt his context,w es tudied the hydrogen-bonding ability of an ovel p-functional core bearing triazine and triazole rings.T he results of our investigation are reported herein.…”

Novel Discotic Boroxines: Synthesis and Mesomorphic Properties

“…However, not only disk-shaped mesogens, but also non-conventional [16] and supramolecular and hydrogen bonded liquid crystals [17] can self-assemble into columnar aggregates. While a variety of LC materials containing heterocyclic 6-membered rings have been synthesized [18], e.g., triazines such as 1 [19–21] or cyclotri­phosphazenes such as 2 [22,23] (Figure 1), surprisingly little is known about liquid crystalline boroxines, the cyclic trimers of organoboronic acids. Aryl boronic acids are valuable reagents for a number of metal-catalyzed reactions, the most prominent one thereof is certainly the Suzuki-Miyaura cross-coupling reaction [24–28].…”