Effect of Hydrogen Bonding and Chirality in Star-Shaped Molecules with Peripheral Triphenylamines: Liquid Crystal Semiconductors and Gels.

Organic semiconductors with well-defined architectures pose a suitable alternative to amorphous silicon-based inorganic semiconductors. Encouraged by the development of organic semiconductors based on columnar liquid crystals, herein, we report on a family of C 3 -symmetric star-shaped mesogens based on triphenylamine (TPA), a functional unit with strong electron donor character. Highly stable columnar phases with high hole mobility values were obtained out of this nonplanar functional unit, and this was achieved by using flexible amide spacers to join the TPA units to a tris(triazolyl)triazine (T) star-shaped core, allowing the formation of intermolecular hydrogen bonds. The presence of hydrogen bonds results in a stabilization of the columnar architectures either in bulk or in the presence of solvents by reinforcing π-stacking and van der Waals interactions, as deduced by Fourier-transform infrared (FTIR) and X-ray diffraction (XRD) studies. Furthermore, the introduction of a stereogenic center in the flexible spacer prompts the formation of chiral aggregates in the liquid crystal state and in the organogel formed in 1-octanol, as demonstrated by circular dichroism spectroscopy.