To obtain a columnar structure with nucleophilic channels embedded in the column centres, we synthesized a series of new crown ether derivatives (compounds 1, 2, and 3) which are composed of a core of dibenzo-24-crown-8 symmetrically surrounded by four identical substituents. Experimental results indicate that compounds 2 and 3 with smaller substituents around the dibenzo-24-crown-8 core form only crystalline phases, while compound 1 bearing larger dendron substituents on the molecular periphery shows multiple liquid crystalline phase transitions. X-ray diffraction demonstrates that 1 can stack parallel to form a hexagonal columnar liquid crystalline (Colh) phase. A stable phase, which renders the diffraction features of a body-centred cubic (BCC) structure and shows unexpected optical anisotropy, is observed in between the Colh and the isotropic state. On the basis of further support from model calculations, we propose that the optically anisotropic âBCCâ structure is an array of ellipsoidal domains placed in the BCC lattice with their long axis along the [111] direction, which results from the periodic density fluctuation of the columns.
为了获得在柱中心嵌入亲核通道的柱状结构,我们合成了一系列新的
冠醚衍
生物(化合物 1、2 和 3),这些衍
生物由二苯并-24-
冠醚-8 核心组成,其周围对称地环绕着四个相同的取代基。实验结果表明,二苯并-24-
冠醚-8 核心周围含有较小取代基的化合物 2 和 3 只形成结晶相,而分子外围含有较大树枝状取代基的化合物 1 则显示出多种液晶相转变。X 射线衍射显示,1 可以平行堆叠形成六角柱状液晶(Colh)相。在 Colh 和各向同性状态之间,还观察到一个稳定的相,它呈现出体心立方(BCC)结构的衍射特征,并显示出意想不到的光学各向异性。在模型计算进一步支持的基础上,我们提出光学各向异性 "BCC "结构是BCC晶格中的椭圆形域阵列,其长轴沿[111]方向,这是柱体周期性密度波动的结果。