School of Chemistry, University of East Anglia, Norwich NR4 7TJ, UK.
J Org Chem. 2012 May 4;77(9):4288-97. doi: 10.1021/jo3002886. Epub 2012 Apr 16.
Substituted triphenylenes and similar discotic molecules have a strong tendency toward columnar organization. Nematic mesophases are much less commonly observed in discotic systems. We have demonstrated a general strategy whereby discotic triphenylenes can be twinned to form stable, boardlike materials that display only nematic mesophases. The dominant structural feature that leads to nematic behavior is an enforced void region in the center of the macrocycle that results from bridging through the triphenylene 3,6-positions. This precludes simple columnar assembly because it would lead to free space through the center of each stack. Selection of appropriate bridging units allows materials to be designed which combine molecular features, such as the optoelectronic properties of electron-rich triphenylenes and conjugated thiophene units, with the processability, self-healing, and alignment features inherent in nematic mesophases. In addition, communication across twinned structures can lead to additional enhancement of optoelectronic behavior. This is particularly apparent in fully conjugated, planar twin 12 which is formally expected to have some antiaromatic character. This character is manifested in its spectral properties, and particularly noteworthy is its strong, Stokes shifted emission at around 500 nm.
取代三联苯和类似的盘状分子具有强烈的柱状组织倾向。向列型中间相在盘状体系中较少见。我们已经证明了一种通用策略，通过该策略可以将盘状三联苯孪晶形成稳定的、板状材料，这些材料只显示向列型中间相。导致向列行为的主要结构特征是在大环的中心强制形成一个空区域，这是通过桥接三联苯的 3,6-位产生的。这排除了简单的柱状组装，因为它会导致每个堆叠的中心有空隙。选择合适的桥接单元可以设计出具有分子特性的材料，例如富电子三联苯和共轭噻吩单元的光电性质，以及向列型中间相固有的加工性、自修复性和取向特性。此外，孪晶结构之间的通信可以导致光电行为的额外增强。这在完全共轭的、平面孪晶 12 中尤为明显，它预计具有一定的反芳香族性质。这种性质在其光谱性质中表现出来，特别值得注意的是其在约 500nm 处的强斯托克斯位移发射。
