Playing with nanosegregation in discotic crown ethers: from molecular design to OFETs, nanofibers and luminescent materials

Abstract

Discotic liquid crystals are promising materials for electronic device applications. Combining extended π-systems with crown ethers may further open access to functional supramolecular hybrid materials. In the present publication, we briefly summarise recent literature developments and focus in a second part on our work in the field of discotic crown ethers. The crown ether derivatives are conveniently accessible by convergent syntheses which allow a high degree of variation with respect to side chains, mesogenic unit, size and symmetry of the crown core, metal complexation and counterion. This set of compounds provides a basis for systematic structureproperty relationship investigations. Numerous experimental studies identified factors being crucial for mesophase stabilisation and geometry and furthermore led to novel room-temperature crown ether mesogens. The latter were obtained by congestion of the mesogenic units and even introduction of peripheral δ-methyl branched side chains. The formation of molybdenum clustomesogens and their application as luminescent hybrid materials is also described.

Game of Crowns: Na+Is Coming! Red NIR-Emissive Hybrid Liquid Crystals Containing Discotic Crown Ethers and Na2Mo6X8iCl6(Xi= Cl or Br)

“…It was shown that such doping could increase the charge carrier mobility and conductivity of H4TP while preserving its columnar arrangement at low doping concentrations. So far, the homogeneous integration of functional inorganic nanocomponents like nanoparticles or nanorods in liquid crystals relies on their functionalization with organic liquid crystalline promoters or compatibilizers by either covalent grafting or electrostatic interactions. ,− Yet, employing soft supramolecular interactions like host–guest interactions has been poorly explored to generate thermotropic LC. − We recently functionalized several 18C6 or 15C5 crown ether backbones to develop nematic and discotic clustomesogens, , i.e., metallic cluster containing liquid crystals. In general, metal clusters are constituted by several metal atoms linked by metal–metal bonds (Figure ).…”

Liquid-crystalline perylene bisimide derivatives bearing an azacrown ether ring complexing with alkaline metal ions

“…54 Supramolecular liquid crystals which exhibited self-organization based on electrostatic interaction between crown-ion complexes and counter anions have been reported previously. [55][56][57][58][59][60][61][62][63][64][65] However, thin film production and insolubilization of thin films of abovementioned LC crown ethers have not studied so far. Electrochemical functions of the LC crown ethers have not been investigated because insoluble thin films in organic solvents could not be produced.…”

Columnar Propeller‐Like 1,3,5‐Triphenylbenzenes: Probing the Effect of Chlorine on the Suzuki Cross‐Coupling and Liquid Crystalline Properties

“…The archetypal discotic liquid crystal contains a central rigid aromatic or heteroaromatic core surrounded by peripheral flexible chains, which self‐assembles into columnar mesophases due to π–π interactions of the core, while the chains stabilize the columnar phase through van der Waals interactions and suppress crystallization due to their flexibility, These self‐assembled structures are interesting because their 1D charge carrier mobility and self‐healing of defects make them suitable for molecular electronics applications , . However, long alkoxy side chains can cause synthetic challenges (e.g., purification and solubility) and furthermore, limit applications by clearing points close to the thermal decomposition temperature , . Thus, discotic liquid crystals where peripheral alkoxy chains have been replaced by some surrogate would be highly attractive.…”