Department of Polymer Chemistry, Kyoto University, Katsura, Kyoto 615-8510, Japan.
J Am Chem Soc. 2012 Feb 29;134(8):3758-65. doi: 10.1021/ja2088053. Epub 2012 Feb 15.
Chirality switching is intriguing for the dynamic control of the electronic and optical properties in nanoscale materials. The ability to photochemically switch the chirality in liquid crystals (LCs) is especially attractive given their potential applications in electro-optic displays, optical data storage, and the asymmetric synthesis of organic molecules and polymers. Here, we present a dynamic photoswitching of the helical inversion in chiral nematic LCs (N*-LCs) that contain photoresponsive axially chiral dopants. Novel photoresponsive chiral dithienylethene derivatives bearing two axially chiral binaphthyl moieties are synthesized. The dihedral angle of the binaphthyl rings changes via the photoisomerization between the open and closed forms of the dithienylethene moiety. The N*-LCs induced by the dithienylethene derivatives that are used as chiral dopants exhibit reversible photoswitching behaviors, including a helical inversion in the N*-LC and a phase transition between the N*-LC and the nematic LC. The present compounds are the first chiral dopants that induce a helical inversion in N*-LC via the photoisomerization between open and closed forms of the dithienylethene moiety.
手性反转在纳米材料中电子和光学性质的动态控制中很有趣。鉴于它们在电光显示器、光学数据存储以及有机分子和聚合物的不对称合成中的潜在应用，光化学切换液晶（LC）中的手性的能力尤其具有吸引力。在这里，我们展示了手性向列相 LC（N*-LC）中的螺旋反转的动态光开关，其中包含光响应的轴向手性掺杂剂。合成了新型光响应的手性二噻吩乙烯衍生物，其具有两个轴向手性联萘部分。通过二噻吩乙烯部分的开环和闭环形式之间的光异构化，改变联萘环的二面角。用作手性掺杂剂的二噻吩乙烯衍生物诱导的 N*-LC 表现出可逆的光开关行为，包括 N*-LC 中的螺旋反转以及 N*-LC 和向列 LC 之间的相变。本化合物是通过二噻吩乙烯部分的开环和闭环形式之间的光异构化诱导 N*-LC 中螺旋反转的第一个手性掺杂剂。
