Chiral azobenzenes can be used as photoswitchable dopants to control supramolecular helices in liquid crystals. However, the lack of thermal stability of the cis‐isomer precludes envisioning the generation of long‐lived supramolecular helices with light. Here, this study demonstrates thermally stable and axially chiral azobenzene switches that can be used as chiral dopants to create supramolecular helices from (achiral) nematic liquid crystals. Their trans‐to‐cis photoisomerization leads to a variation of helical twisting power that reaches up to 60%, and the helical superstructure that is engineered with light displays a relaxation time that reaches tens of hours. These results demonstrate that combining ortho‐fluorination with axial chirality in molecular photoswitches constitutes an efficient strategy to promote long‐lived helical states. Further, this approach shows potential to design supramolecular machines that are controlled by light entirely.

中文翻译：

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氟化光电开关促进的超分子超长寿命螺旋

手性偶氮苯可以用作光可切换掺杂剂，以控制液晶中的超分子螺旋。但是，由于缺乏顺式异构体的热稳定性，因此无法预料到有光会产生长寿命的超分子螺旋。在这里，这项研究证明了热稳定性和轴向手性偶氮苯开关可以用作手性掺杂剂，以从（非手性）向列型液晶产生超分子螺旋。他们的反式-到-顺光致异构化导致螺旋扭曲力的到达高达60％的变化，那就是设计与光显示器弛豫时间的到达几十个小时的螺旋上层建筑。这些结果表明，结合邻位分子光开关中具有轴向手性的氟化是促进长寿命螺旋态的有效策略。此外，这种方法显示出设计完全由光控制的超分子机器的潜力。