Construction And Functionalization Of ALS Type Supramolecular Assembly System

Chirality is a basic characteristic of life in nature.By means of molecular assembly and intermolecular interaction,molecular chirality is transmitted and amplified to a certain extent,thus supramolecular chirality can be expressed.Because of the natural chiral structure of steroids,steroids derivatives based on aromatic functional group-Linking-Steroidal(ALS)have been widely used in gel materials and chiral liquid crystals.We constructed a series of ALS type supramolecular assembly systems by combining steroid structures with photoresponsive groups,and further studied their photoresponsive,chiral liquid crystal and circular polarization luminescence properties.In chapter 2,we synthesized an ALS type cholesterol derivative(CSAzPy)containing azopyridine,and endowed it with multiple functions:it can be both chiral and photoresponsive,and it can also combine metal,hydrogen bond donor and halogen bond donor to obtain a series of new complexes.In addition to the photoresponsive metal gel CSAzPy-Ag,the liquid crystal properties of CSAzPy and its hydrogen bond and halogen bond complexes were studied in detail.CSAzPy and most of its complexes form smectic phase and can respond to light reversibly.In order to enrich chiral liquid crystals,we constructed a series of chiral nematic liquid crystals with different pitch with fingerprint texture,namely cholesteric liquid crystals,using CSAzPy and its complexes as dopants in nematic liquid crystal 5CB as the subject.Due to the presence of azobenzene structure,the liquid crystals can respond to ultraviolet light quickly and sensitively,thus obtaining cholesteric liquid crystal materials with reversible photoresponse.In chapter 3,circularly polarized luminescence(CPL)materials with a large luminescence dissymmetry factor(g_lum)and multi-color properties are very attractive.While multi-color tunable CPL can be realized by different organic dyes,the challenge of realizing both a higher g_lum and multiple colors using a single component remains.Here,we design an aggregation-induced emission(AIE)fluorophore,which is a pyridine functionalized cyanostilbene attached to a chiral unit,and realize multi-color tunable CPL with a high g_lum.The compound can self-assemble into a nanohelix and form both gel and xerogel films,exhibiting blue CPL with large g_lumvalues of-3.0?10^-2 and-1.7?10^-2,respectively.With the assistance of pyridine protonation,the xerogel films exhibit red-shifted CPL signals from 480 nm to 530 nm,covering from blue via green and yellow to orange.Additionally,the g_lum remains constant during the process,and the CPL materials with large asymmetry factor(g_lum)and polychromatic properties are obtained.