ABSTRACT

Two novel chiral fluorescent photoswitches bearing unsymmetric α-cyanothienylethene as emissive/photosensitive scaffold and bridged binaphthyl moieties as chiral entities are synthesised. The effects of the position of cyano group in switch 8 and 9 on the photoluminescence and photoresponsive properties of them in organic solvent and cholesteric liquid crystals (Ch-LCs) are explored. Both of these two photoswitches undergo partial reversible Z/E photoisomerisation accompanied by changes in fluorescence intensity under the light irradiations in both organic solvent and LC media. However, fluorescence quantum yields of switch 8 are much higher than those of switch 9. Meanwhile, the initial helical twisting power (HTP) value of switch 8 in LC media is much higher than that of switch 9, which is ascribed to their distinct geometries arising from different positions of cyano group on the C=C bond in them. Moreover, the switch 8-doping Ch-LC system exhibits more fast response and better reversible switching behaviours compared to Ch-LC system containing switch 9. Finally, simultaneous photoswitching of the reflection colour and fluorescence intensity in the Ch-LC sample is demonstrated. This work provides an idea for designing chiral fluorescent photoswitches with advanced photoluminescence and photoswitching characteristics.

摘要

合成了两个新颖的手性荧光光开关，它们带有不对称的α-氰基噻吩基乙烯作为发光/光敏支架和桥接的联萘基部分作为手性实体。探索了开关8和9中氰基的位置对它们在有机溶剂和胆甾型液晶（Ch-LCs）中的光致发光和光响应特性的影响。在有机溶剂和LC介质中，在光照射下，这两个光开关均发生部分可逆的Z / E光异构化，并伴随荧光强度的变化。但是，开关8的荧光量子产率比开关9的荧光量子产率高得多。同时，开关8在LC介质中的初始螺旋扭曲功率（HTP）值比开关9的初始螺旋扭曲功率（HTP）值高得多。这归因于它们中不同的几何形状，这是由于它们中C = C键上的氰基位置不同所致。此外，与包含开关9的Ch-LC系统相比，开关8掺杂的Ch-LC系统显示出更快的响应和更好的可逆转换行为。最后，展示了同时进行Ch-LC样品中反射色和荧光强度的光开关。这项工作为设计具有先进的光致发光和光开关特性的手性荧光光开关提供了一个思路。展示了Ch-LC样品中反射色和荧光强度的同时光开关。这项工作为设计具有先进的光致发光和光开关特性的手性荧光光开关提供了一个思路。展示了Ch-LC样品中反射色和荧光强度的同时光开关。这项工作为设计具有先进的光致发光和光开关特性的手性荧光光开关提供了一个思路。