Influence of Helical Twisting Power on the Photoswitching Behavior of Chiral Azobenzene Compounds: Applications to High-Performance Switching Devices
作者:Md. Zahangir Alam、Teppei Yoshioka、Tomonari Ogata、Takamasa Nonaka、Seiji Kurihara
DOI:10.1002/chem.200600954
日期:2007.3.16
Five photochromic chiral azobenzene compounds and one nonphotochromic chiral compound were synthesized and characterized by IR, 1H NMR spectroscopy, and elemental analysis. Cholesteric liquid crystalline phases were induced by mixing of the nonphotochromic chiral compound and one of the photochromic chiral azobenzene compounds in a host nematic liquid crystal (E44). The helical pitch of the induced
合成了5个光致变色手性偶氮苯化合物和1个非光致变色手性化合物,并通过IR,1H NMR光谱和元素分析对其进行了表征。通过将非光致变色手性化合物与光致变色手性偶氮苯化合物之一在主体向列液晶(E44)中混合来诱导胆甾型液晶相。通过卡诺楔形法确定诱导的胆甾相的螺旋螺距,并由此确定每个样品的螺旋扭转力(HTP)。由于偶氮苯分子的反式-顺式光致异构化,紫外线辐射下偶氮苯化合物的螺旋扭曲能力降低。在我们的研究中合成的偶氮苯化合物Azo-5,以异甘露聚糖(自由基)为手性光致变色掺杂剂,显示最高的HTP和对比度(Tmax / Tmin)。通过分别用紫外线和可见光照射,手性偶氮苯分子的可逆反式-顺式光致异构化,实现了补偿向列相和胆甾相之间的光转换。在诱导的胆甾相中,传输速率(对比度)随着螺旋螺距长度的减小而增加。详细讨论了螺旋扭转能力对手性偶氮苯化合物光开关行为的影响。在诱导的胆甾相中,传输速率(对比度)随