At the Limits of Liquid Crystallinity: Stimuli Responsive 3D Columnar Liquid Crystals and Soft Crystals of Supramolecular Anthracene Mesogens

At the Limits of Liquid Crystallinity: Stimuli Responsive 3D Columnar Liquid Crystals and Soft Crystals of Supramolecular Anthracene Mesogen

To be or not to be – nematic liquid crystals from shape-persistent V-shaped nematogens with the ‘magic angle’

<p>The tetrahedral bending angle in V-shaped nematogens was claimed to be the optimum for finding a biaxial nematic liquid crystal phase. The benzo[1,2-b:4,3-b’]dithiophene core, recently successfully applied as a tetrahedral bending unit in mesogens with lateral flexible chains, is here embedded in a scaffold with only terminal chains, which conventionally promotes the formation of nematic phases at low temperature. A series of new mesogens has been successfully prepared, realising hockey-stick, hockey-stick dimer and V-shaped molecular topologies. Only the hockey-stick mesogens assemble in uniaxial nematic phases over a broad temperature range. Single crystal structure analysis of a hockey-stick and V-shaped compound reveal remarkable similarities with the benzodithiophene core wrapped by aliphatic chains. A model explaining the absence of nematic mesophases in the family of V-shaped, shape-persistent mesogens with terminal aliphatic chains is presented and results in the proposal of a new design for biaxial nematogens.</p

To be or not to be – nematic liquid crystals from shape-persistent V-shaped nematogens with the ‘magic angle’

<p>The tetrahedral bending angle in V-shaped nematogens was claimed to be the optimum for finding a biaxial nematic liquid crystal phase. The benzo[1,2-b:4,3-b’]dithiophene core, recently successfully applied as a tetrahedral bending unit in mesogens with lateral flexible chains, is here embedded in a scaffold with only terminal chains, which conventionally promotes the formation of nematic phases at low temperature. A series of new mesogens has been successfully prepared, realising hockey-stick, hockey-stick dimer and V-shaped molecular topologies. Only the hockey-stick mesogens assemble in uniaxial nematic phases over a broad temperature range. Single crystal structure analysis of a hockey-stick and V-shaped compound reveal remarkable similarities with the benzodithiophene core wrapped by aliphatic chains. A model explaining the absence of nematic mesophases in the family of V-shaped, shape-persistent mesogens with terminal aliphatic chains is presented and results in the proposal of a new design for biaxial nematogens.</p

Solid-state assisted synthesis of oligobenzoates

<div><p>The solid-state assisted synthesis opens an easy access to oligobenzoates end-capped with gallic acid, protocatechuic acid or 4-hydroxybenzoic acid etherified with long flexible chains – which are important precursors for liquid crystalline materials. The latter may consist of aliphatic, oligoethyleneoxy and semiperfluorinated chains. The rapid preparation of oligoesters with different peripheries is demonstrated.</p></div

A Convergent Continuous Multistep Process for the Preparation of C₄‑Oxime-Substituted Thiazoles

We report a strategy designed for the rapid and convergent assembly of C₄-oxime substituted thiazoles. Our approach relied on 3-bromo-2-oxopropanal <i>O</i>-methyl oxime <b>7</b> as a key building block. A three-step sequence to <b>7</b> was designed, which, for safety concerns, could only be operated in batch mode on limited scales (≪100 g). We describe herein how we addressed such a limitation, by designing a multistep continuous synthesis of this intermediate and further demonstrate the advantages of flow reactor configuration upon scaling up