A novel liquid crystal core unit 5,6-dihydro-4H-cyclopenta[b]thiophene was designed and synthesized in four steps and three mesogens containing terminal cyano group were then obtained. The effects of this skeleton on the mesophase and physical properties of liquid crystals were then investigated by compared with two series of reference compounds based on 1,4-disubstituted phenylene and disubstituted phenylcyclohexane and found this unit can benefit the formation of the nematic phase. Besides, both the birefringence (Δn) and dielectric anisotropy (Δε) values were increased after the introduction of this core unit. Density function theory calculations suggested that the combination of thiophene and cyclopentane had increased the height/width ratio and linearity of the mesogens which can stabilise the liquid crystal phase. Five different liquid crystals based on this new core were synthesized at last to further illustrate the usefulness of this core in constructing high birefringence and large dielectric anisotropy liquid crystals with wide nematic phase interval.

中文翻译：

---

5,6-二氢-4H-环戊[b]噻吩基向列液晶的合成与性质：一种具有高双折射和大介电各向异性的介相体的新途径


设计并分 4 个步骤设计合成了一种新型液晶核心单元 5,6-二氢-4H-环戊[b]噻吩，然后获得了 3 个含有末端氰基的介原。然后通过与基于 1,4-二取代苯和二取代苯基己烷的两系列参考化合物进行比较，研究了该骨架对液晶中间相和物理性质的影响，发现该单元有利于向列相的形成。此外，引入该核心单元后，双折射 （Δn） 和介电各向异性 （Δε） 值均有所增加。密度函数理论计算表明，噻吩和环戊烷的组合增加了中间原体的高/宽比和线性度，从而可以稳定液晶相。最后，基于这种新核心合成了 5 种不同的液晶，以进一步说明该核心在构建具有宽向列相间隔的高双折射和大介电各向异性液晶中的有用性。