Parallel Polar Dimers in the Columnar Self‐Assembly of Umbrella‐Shaped Subphthalocyanine Mesogens

The self‐assembly of umbrella‐shaped mesogens is explored with subphthalocyanine cores and oligo(thienyl) arms with different lengths in the light of their application as light‐harvesting and photoconducting materials. While the shortest arm derivatives self‐assemble in a conventional columnar phase with a single mesogen as a repeating unit, the more extended derivatives generate dimers that pile up into liquid crystalline columns. In contrast to the antiparallel arrangement known from single crystals, the present mesogens align as parallel dimers in polar columnar phases as confirmed by X‐ray scattering, experimental densities, dielectric spectroscopy, second harmonic generation, alignment, and conductivity studies. UV–vis and fluorescence spectroscopies reveal a broad absorption in the visible range and only weak emission of the Q‐band. Thus, these light‐collecting molecules forming strongly polar columnar mesophases are attractive for application in the area of photoconductive materials. The combination of a subphthalocyanine core with oligothiophene arms results in strongly absorbing umbrella‐shaped mesogens. They assemble in enantiotropic and low clearing columnar liquid crystals. Nanosegregation and space‐filling lead to unique polar parallel dimers, which subsequently allows for a facile and complete alignment of the mesophase in an electric field.