Preparation of Monocyclic Liquid Crystals

一般来说，液晶的核心结构至少由两个环系组成。六元环被用作核心部分，而较宽的对流层面则不太受欢迎。2-酰基氧基tropone的酰基可以在C-1和C-2的两个氧原子之间迁移，称为[1,9]异位性，这有助于介生。[1,9]信号性使分子沿较长的分子轴定向，呈现中间相。单环对流层体(1)表现为单向近晶A相。伪五元环通过[1,9]符号异位形成以辅助中间相的出现。预计单环液晶具有较低的粘度。第二个单环液晶2也表现为单向近晶a相。为了提高单环液晶的热稳定性，在烷基侧链上引入了双键。3的热稳定性与2相似。化合物3 （m=15, n=11和m=18, n=11）存在中间相，对应的化合物2 （m=15, n=13和m=18, n=13）不存在中间相。侧链中的双键延伸了3的核心部分。因此，具有双键(s)的化合物，如4和5，将比13更具介生性。因此，在苯类化合物中没有观察到的七元交叉共轭化合物的特征动力学性质对中间相的外观起作用。值得注意的是，单环液晶的成功制备不仅在于制备了低粘性液晶，而且修改了液晶的核心部分必须至少有两个环。< <化学式> >

Generally, the core structure of liquid crystals consists of at least two ring systems. Six-membered rings are used as a core moiety and a wider troponoid is less favored.An acyl group of 2-acyloxytropones can migrate between the two oxygen atoms of C-1 and C-2, so-called [1, 9] sigmatropy, which assisted to be mesogenic. The [1, 9] sigmatropy made molecules orientated along the longer molecular axis to exhibit the mesophase. A monocyclic troponoid (1) showed a monotropic smectic A phase. A pseudo five-membered ring was formed to assist the appearance of the mesophase by the [1, 9] sigmatropy. It is anticipated that monocyclic liquid crystals have low viscosity.The second monocyclic liquid crystals 2 also showed a monotropic smectic A phase. In order to increase the thermal stability of the monocyclic liquid crystals, a double bond was introduced into an alkyl side chain. The thermal stability of 3 was similar to that of 2. While compounds 3 (m=15, n=11 and m=18, n=11) showed a mesophase, corresponding 2 (m=15, n=13 and m=18, n=13) did not. The double bond in the side chain extended the core part of 3. Compounds with double bond (s) such as 4 and 5, therefore, would be more mesogenic than 13. Thus, the characteristic dynamic property of the seven-membered cross conjugated compounds, which does not observe in benzenoids, worked on the appearance of the mesophase.It is noteworthy to succeed the preparation of monocyclic liquid crystals in terms of not only preparing low viscous liquid crystals, but revising that the core part of liquid crystals has to have at least two rings.<<chemical formula>>