The synthesis of [1,2,3]-triazole-based bent core liquid crystals via microwave-mediated ‘Click Reaction’ and their mesomorphic behaviour

<p>A series of [1,2,3]-triazole-based liquid crystal compounds were synthesised via a fast and efficient microwave-mediated ‘Click Reaction’ and their phase behaviour is presented. Most of the 1,4-diaryl-[1,2,3]-triazole compounds exhibited a nematic phase with broad temperature ranges and relatively low transition temperatures compared to previously examined materials. Structural variations, involving regio-isomers and lateral halogenation, gave rise to different phase behaviour of the two families of triazole-based compounds.</p> <p>Two groups of [1,2,3]-triazoyl-based liquid crystalline compounds obtained in this work. R₁, R₂ H, alkyl, alkoxy, CN, Cl, F, etc; X = H, Cl, F.</p

Small-Molecule Labeling of Live Cell Surfaces for Three-Dimensional Super-Resolution Microscopy

Precise imaging of the cell surface of fluorescently labeled bacteria requires super-resolution methods because the size-scale of these cells is on the order of the diffraction limit. In this work, we present a photo­controllable small-molecule rhod­amine spiro­lactam emitter suitable for non-toxic and specific labeling of the outer surface of cells for three-dimensional (3D) super-resolution (SR) imaging. Conventional rhod­amine spiro­lactams photo­switch to the emitting form with UV light; however, these wavelengths can damage cells. We extended photo­switching to visible wavelengths >400 nm by iterative synthesis and spectroscopic characterization to optimize the substitution on the spiro­lactam. Further, an <i>N</i>-hydroxy­succinimide-functionalized derivative enabled covalent labeling of amines on the surface of live <i>Caulobacter crescentus</i> cells. Resulting 3D SR reconstructions of the labeled cell surface reveal uniform and specific sampling with thousands of localizations per cell and excellent localization precision in <i>x</i>, <i>y</i>, and <i>z</i>. The distribution of cell stalk lengths (a sub-diffraction-sized cellular structure) was quantified for a mixed population of cells. Pulse-chase experiments identified sites of cell surface growth. Covalent labeling with the optimized rhod­amine spiro­lactam label provides a general strategy to study the surfaces of living cells with high specificity and resolution down to 10–20 nm

Small-Molecule Labeling of Live Cell Surfaces for Three-Dimensional Super-Resolution Microscopy

Precise imaging of the cell surface of fluorescently labeled bacteria requires super-resolution methods because the size-scale of these cells is on the order of the diffraction limit. In this work, we present a photo­controllable small-molecule rhod­amine spiro­lactam emitter suitable for non-toxic and specific labeling of the outer surface of cells for three-dimensional (3D) super-resolution (SR) imaging. Conventional rhod­amine spiro­lactams photo­switch to the emitting form with UV light; however, these wavelengths can damage cells. We extended photo­switching to visible wavelengths >400 nm by iterative synthesis and spectroscopic characterization to optimize the substitution on the spiro­lactam. Further, an <i>N</i>-hydroxy­succinimide-functionalized derivative enabled covalent labeling of amines on the surface of live <i>Caulobacter crescentus</i> cells. Resulting 3D SR reconstructions of the labeled cell surface reveal uniform and specific sampling with thousands of localizations per cell and excellent localization precision in <i>x</i>, <i>y</i>, and <i>z</i>. The distribution of cell stalk lengths (a sub-diffraction-sized cellular structure) was quantified for a mixed population of cells. Pulse-chase experiments identified sites of cell surface growth. Covalent labeling with the optimized rhod­amine spiro­lactam label provides a general strategy to study the surfaces of living cells with high specificity and resolution down to 10–20 nm

Synthesis and properties of hydroxy tail-terminated cyanobiphenyl liquid crystals

<p>Two series of new hydroxy tail-terminated cyanobiphenyl compounds are described. The 4′-ω-hydroxyalkynyl-4-cyanobiphenyl compounds (<b>1a</b>–<b>1g</b>) were synthesised as the key intermediates to the 4′-?ω-hydroxyalkyl-4-cyanobiphenyl compounds (<b>2a</b>–<b>2g</b>) obtained upon reduction of the acetylenes. Many of these ω-hydroxyalkynyl and ω-hydroxyalkyl cyanobiphenyl compounds exhibit nematic mesophases and they also serve as precursors for the synthesis of other interesting materials. Using density functional theory, we calculate the dipole moment of all relevant ω-hydroxyalkynyl and ω-hydroxyalkyl cyanobiphenyl compounds and find a correlation between the calculated dipole moments and measured crystalline to nematic or isotropic liquid transition temperatures.</p

Design of Chemoresponsive Liquid Crystals through Integration of Computational Chemistry and Experimental Studies

We report the use of computational chemistry methods to design a chemically responsive liquid crystal (LC). Specifically, we used electronic structure calculations to model the binding of nitrile-containing mesogens (4′-<i>n</i>-pentyl-4-biphenylcarbonitrile) to metal perchlorate salts (with explicit description of the perchlorate anion), which we call the coordinately saturated anion model (CSAM). The model results were validated against experimental data. We then used the CSAM to predict that selective fluorination can reduce the strength of binding of nitrile-containing nematic LCs to metal-salt-decorated surfaces and thus generate a faster reordering of the LC in response to competitive binding of dimethylmethylphosphonate (DMMP). We tested this prediction via synthesis of fluorinated compounds 3-fluoro-4′-pentyl­[1,1′-biphenyl]-4-carbonitrile and 4-fluoro-4′-pentyl-1,1′-biphenyl, and subsequent experimental measurements of the orientational response of LCs containing these compounds to DMMP. These experimental measurements confirmed the theoretical predictions, thus providing the first demonstration of a chemoresponsive LC system designed from computational chemistry