We report the synthesis and characterization of two new chiral 1,3-phenylene based five ring bent-core mesogens that combine the unique electro-optic characteristics of banana-shaped molecules with chiroptic properties. Azobenzene moiety incorporated as a linking unit in one of the rigid arms renders trans–cis isomerization property to the molecules while chirality is introduced by tethering chiral aliphatic terminal chains. Both compounds can self-organize into helical superstructure, i.e. cholesteric mesophase, which can selectively reflect light. The novelty of the helical self-organized superstructure reported here lies in its low molecular weight single component molecular system that is truly multifunctional so that the reflection band is tunable by three different external stimuli, i.e. temperature, light and electric field. A red shift in reflection colors is obtained by changing the temperature on cooling and by UV irradiation while a blue shift is seen by electrical field application. Due to the high applicability of azobenzene-doped liquid crystalline systems, we also evaluated the efficiency of these chiral bent-core molecules as chiral transfer agents and found that they behave similar to rod-shaped dopants whose chirality is a consequence of the presence of one chiral center.
我们报道了两种新型基于1,3-苯基的手性五环弯曲核心介晶的合成与表征,这些分子结合了香蕉形状分子独特的电光特性和手性光学性质。其中一个刚性臂中的
偶氮苯部分作为连接单元赋予分子反式-顺式异构化性质,而通过连接手性脂肪族末端链引入手性。这两种化合物均能自发组织成螺旋超结构,即胆甾型介晶相,能够选择性地反射光。这里报道的螺旋自发组织超结构的独特之处在于其低分子量的单一组分分子系统真正具有多功能性,使得反射带可通过三种不同的外部刺激进行调节,即温度、光和电场。通过冷却改变温度和紫外线照射可获得反射颜色的红移,而通过电场应用可观察到蓝移。由于
偶氮苯掺杂的液晶系统的高应用性,我们还评估了这些手性弯曲核心分子的手性传递效率,发现它们的行为类似于棒状掺杂剂,其手性是由于存在一个手性中心所导致。