Diketopyrrolopyrrole Columnar Liquid‐Crystalline Assembly Directed by Quadruple Hydrogen Bonds

A diketopyrrolopyrrole (DPP) dye self‐assembles via a unique hydrogen‐bonding motif into an unprecedented columnar liquid‐crystalline (LC) structure. X‐ray and polarized FTIR experiments reveal that the DPPs organize into a one‐dimensional assembly with the chromophores oriented parallel to the columnar axis. This columnar structure is composed of two π–π‐stacked DPP dimers with mirror‐image configurations that stack alternately through quadruple hydrogen bonding by 90° rotation. This exotic packing is dictated by the complementarity between H‐bonds and the steric demands of the wedge‐shaped groups attached at the core. This novel LC supramolecular material opens a new avenue of research on DPP dye assemblies with photofunctional properties tailored by H‐bonding networks.     

Ferroelectrically Switching Helical Columnar Assembly Comprising Cisoid Conformers of a 1,2,3‐Triazole‐based Liquid Crystal

The 1,2,3‐triazole molecule, which is a product of click chemistry, possesses a high dipole moment and can be a useful polar motif for ferroelectric columnar liquid crystal (LC) materials—though it has not been used to date. Herein, we report the helical assembly and ferroelectric switching properties of a columnar liquid crystal comprising a naphthalene core and 1,2,3‐triazolyl linkages. The molecule assembles into a double‐stranded helical columnar LC structure (Col_hel). The X‐ray simulations of cisoid and transoid columnar models suggest that the helical assembly comprises cisoid conformers with a non‐zero dipole moment. The helical columns in the Col_hel phase are aligned homeotropically under an electric field. The ferroelectric switching of the axial polarization can be observed in the temperature range of 105–115 °C in the Col_hel phase, wherein the triazolyl hydrogen bonding along the column axis is weakened. The ferroelectric switching event is attributed to the rotation of the polar triazolyl units in response to the electric field.