ABSTRACT

Six novel phenyl-tolane type liquid crystals based on 5,6-dihydro-4 H-cyclopenta[b]thiophene core were designed and synthesised by Sonogashira coupling reactions in high yields. Two reference compounds were then used to clarify the effects of this new core on the mesomorphic behaviours and physical properties of phenyl-tolane type mesogens and found that these new core-based mesogens possessed wider mesophase ranges. Both the birefringence (Δn) and dielectric anisotropy (Δε) values were increased after the employment of this new core, offering an alternative option for the design and synthesis of high-performance phenyl-tolanes. The geometry, ultraviolet absorption, polarisability (α) and dipole moment (μ) of two representative compounds and their references were calculated by density functional theory to correlate the structure–property relationship of the new mesogens. The calculated energy minimum structures of the new mesogens showed well linearity and the molecular length/width ratio was increased, which would benefit the formation of the nematic phase. The orders of the calculated polarisability (α) and dipole moment (μ) of two representative compounds and their references were in accordance with the sequences of the measured birefringence (Δn) and dielectric anisotropy (Δε) values, respectively, which might shed light on the correlation between microscopic molecular structure and macroscopic physical properties.

摘要

基于5,6-二氢-4-六新颖苯基二苯乙炔型液晶 ħ环戊二烯并[ b ]噻吩核心设计并通过Sonogashira偶联以高产率反应来合成。然后使用两种参考化合物来阐明这种新核对苯基甲苯类介晶的介晶行为和物理性质的影响，并发现这些新的基于核的介晶具有更宽的中间相范围。使用这种新核心后，双折射 (Δ n ) 和介电各向异性 (Δ ε ) 值都增加了，为高性能苯基甲苯烷的设计和合成提供了另一种选择。几何形状、紫外吸收、极化率 ( α ) 和偶极矩 (μ ) 两种代表性化合物及其参考文献通过密度泛函理论计算，以关联新介晶的结构-性质关系。计算出的新介晶的能量最小结构表现出良好的线性，分子长/宽比增加，有利于向列相的形成。两种代表性化合物及其参考的计算极化率 ( α ) 和偶极矩 ( μ ) 的顺序分别与测量的双折射 (Δ n ) 和介电各向异性 (Δ ε ) 值的顺序一致，这可能会导致阐明微观分子结构与宏观物理性质之间的相关性。