Anthraquinone-based discotic liquid crystals

Phase Behavior of a New Class of Anthraquinone-Based Discotic Liquid Crystals

Five novel columnar liquid crystalline compounds (4.1-4.5) consisting of a central anthraquinone core carrying four alkoxy chains (R = n-C₆H₁₃, n-C₈H₁₇, n-C₁₀H₂₁, n-C₁₂H₂₅, and 3,7-dimethyl octyl) with two diagonally opposite 1-ethynyl-4-pentylbenzene units were synthesized, and their phase transitions were investigated between changes in the molecular structure and their self-assembly into the columnar mesophases. Small and wide-angle X-ray scattering (SAXS/WAXS) studies were performed to deduce the exact nature of the mesophases, and their corresponding electron density maps were derived from the intensities of the peaks observed in the diffraction patterns. A comparison of compounds with different alkoxy chains indicated that the soft crystal columnar rectangular (Cr_colrec) phase was stable at lower temperature for the shortest peripheral alkoxy chain (4.1; R = n-C₆H₁₃) and was found to exhibit the columnar hexagonal (Col_h) phase and then the discotic nematic (N_D) phase with increasing temperature. In contrast, increasing the peripheral chain length to n-C₈H₁₇ or the branched one (4.2 and 4.5) stabilized the Col_h phase at lower temperature and showed the N_D phase at higher temperature. Further increase in chain length (4.3 and 4.4; n-C₁₀H₂₁, n-C₁₂H₂₅) demonstrated the formation of the N_D phase. Conductivity measurement in the Col_h mesophase was found to be almost 10 times higher in magnitude than the corresponding Cr_colrec phase. The HOMO-LUMO band gap of all the compounds was found to be in the range from 2.79 to 2.82 eV, which is quite less and comparable with the optical energy band gap.

Dual-Responsive Lipid Nanotubes: Two-Way Morphology Control by pH and Redox Effects

Lipid nanotubes are the preferred structures for many applications, especially biological ones, and thus have attracted much interest recently. However, there is still a significant need for developing more lipid nanotubes that are reversibly controllable to improve their functionality and usability. Here, we presented a two-way reversible morphology control of the nanotubes formed by the recently designed molecule AQUA (C25H29NO4). Because of its special design, the AQUA has both pH-sensitive and redox-active characters provided by the carboxylic acid and anthraquinone groups. Upon chemical reduction, the nanotubes turned into thinner ribbons, and this structural transformation was significantly reversible. The reduction of the AQUA nanotubes also switched the nanotubes from electrically conductive to insulative. Nanotube morphology can additionally be altered by decreasing the pH below the pKa value of the AQUA, at ∼4.9. Decreasing the pH caused the gradual unfolding of the nanotubes, and the interlayer distance in the nanotube's walls increased. This morphological change was fast and reversible at a wide pH range, including the physiological pH. Thus, the molecular design of the AQUA allowed for an unprecedented two-way and reversible morphology control with both redox and pH effects. These unique features make AQUA a very promising candidate for many applications, ranging from electronics to controlled drug delivery.

Anthra- and pentacenequinone derivatives: influence of structure on the formation of columnar liquid crystal phases

The mesomorphic properties of novel acenequinones reveals that a perpendicular packing motif is an important factor for determining mesophase stability.

Synthesis, structure and properties of polysubstituted benzo[g]chrysene by FeCl3-promoted from diphenylacetypene and phenylacetaldehyde derivatives

Benzo[g]chrysene (BgCh) is a new untapped virgin land in PAHs. A new and straightforward method has been developed to synthesize it. Part of BgCh revealed liquid crystalline properties and their fluorescence emission wavelength is in the range of blue light.