Self-Assembly of Board-Shaped Diketopyrrolopyrrole and Isoindigo Mesogens into Columnar π-π Stacks

Columnar Mesomorphism of Board-Shaped Perylene, Diketopyrrolopyrrole, Isoindigo, Indigo, and Quinoxalino-Phenanthrophenazine Dyes

The properties of organic dyes depend as much on their intermolecular interactions as on their molecular structure. While it is generally predictable what supramolecular structure would be ideal for a specific application, the generation of specific supramolecular structures by molecular design and suitable processing methods remains to be a challenge. A versatile approach to different supramolecular structures has been the application of mesomorphism in conjunction with alignment techniques and self-assembly at interfaces. Reviewed here is the columnar mesomorphism of board-shaped dyes perylene, indigo, isoindigo, diketopyrrolopyrrole, and quinoxalinophenanthrophenazine. They generate a larger number of different supramolecular structures than conventional disc-shaped (discotic) mesogens because of their non-circular shape and directional intermolecular interactions. The mesomorphism of all but the perylene derivatives is systematically and comprehensively covered for the first time.

Butterfly-like Shape Liquid Crystals Based Fused-Thiophene as Unidimensional Ambipolar Organic Semiconductors with High Mobility

Mesomorphous butterfly-like shape molecules based on benzodithiophene, benzodithiophene-4,8-dione and cyclopentadithiophen-4-one core moieties were efficiently synthesized by the Suzuki-Miyaura coupling and Scholl oxidative cyclo-dehydrogenation reactions' tandem. Most of the butterfly molecules spontaneously self-organize into columnar hexagonal mesophase. The electron-deficient systems possess strong solvent-gelling ability but are not luminescent, whereas the electron-rich terms do not form gels but strongly emit light between 400 and 600 nm. The charge carrier mobility was also measured by time-of-flight transient photocurrent technique in the mesophases for some of the compounds. They display hole-transport performances with positive charge mobility in the 10^-3  cm^-2  V^-1  s^-1 range, consistent with the high degree of ordering and stability of the columnar superstructures. In particular, the mesogen with a benzodithiophen-4,8-dione core shows ambipolar charge carrier transport with both high electron (μ_e =6.6×10^-3  cm^-2  V^-1  s^-1 ) and hole (μ_h =4.5×10^-3  cm^-2  V^-1  s^-1 ) mobility values.