Nonsymmetrical cholesterol dimers constituting regioisomeric oxadiazole and thiadiazole cores: an investigation of the structure–property correlation
作者:Balaram Pradhan、Nirmalangshu Chakraborty、Ravindra Kumar Gupta、G. Shanker、Ammathnadu S. Achalkumar
DOI:10.1039/c6nj03141b
日期:——
Three series of chiral nonsymmetrical dimers were prepared by connecting promesogenic cholesterol to a bent structure derived from a substituted 1,3,4-oxadiazole or 1,2,4-oxadiazole or 1,3,4-thiadiazole moiety. These two mesogenic segments are interconnected through spacers of varying lengths and parity. The structures of the bent achiral unit were systematically varied with different central heterocyclic
通过将促生胆固醇与衍生自取代的1,3,4-恶二唑或1,2,4-恶二唑或1,3,4-噻二唑部分的弯曲结构连接,制备了三个系列的手性非对称二聚体。这两个介晶链段通过长度和奇偶性不同的间隔子相互连接。弯曲的非手性单元的结构随中央杂环的不同而系统地变化,以了解弯曲角度对热和胶凝行为的影响。由杂环核决定的非手性单元的弯曲角在受挫相的稳定中起主要作用。基于1,3,4-恶二唑单元的二聚体具有更弯曲的结构,可稳定受挫相(如蓝相和扭曲晶界相)。具有较大弯曲角度的弯曲系统优选用于稳定手性向列相和近晶A相。有趣的是,与基于1,3,4-恶二唑单元的二聚体一样,增加的弯曲结构降低了中间相的稳定性,在该二聚体中,许多化合物均表现出单相相。在具有较大弯曲角的二聚体的情况下,观察到对映的同构。所有化合物在溶液中均显示蓝光发射。在这些手性二聚体中,只有基于1,3,4-恶二唑单元的化合物才具有胶凝能力,这强调了弯曲角度,偶极