Synthesis And Properties Of Novel Chiral Luminescent Derivatives Based On Cyanostilbene

In recent decades,the application scope of luminescent materials has become wider and wider,but for most traditional luminescent molecules in the aggregated or solid state,they will emit fluorescence quenching（Aggregataion-caused quenching,ACQ）phenomenon,which limits their application scope.In 2001,Benzhong Tang research group revealed for the first time the phenomenon that stronger fluorescence can be generated in the aggregation state.This phenomenon is just the opposite of ACQ performance,which is called aggregation-induced emission（AIE）.Among the currently prepared AIE molecules,cyanostilbene has been widely used due to its simple structure,high luminous efficiency,convenient synthesis,and easy modification.At present,cyanostilbene derivatives have been widely used in chemical sensors,optoelectronic components,bioimaging technology and other application fields,but the application of cyanostilbene in circularly polarized luminescence materials is still less.Circularly polarized luminescence（CPL）material is an optically active material that can emit left-or right-handed polarized light under the action of an excitation light source,It has great application value in the fields of chiral detection,optical information,3D display,and chiral catalytic synthesis.The fluorescence quantum yield（Ф_F）and luminescence asymmetry factor(g_lum)are commonly used to evaluate CPL active materials.In order to obtain higherФ_Fand g_lum,optimized molecular structures or self-assembled structures are currently mainly used.In this paper,cyanostilbene is used as the luminescent core,and then combined with chiral molecules R-binaphthol,（1R,2R）-1,2-cyclohexanediamine and L-（+）-dimethyl tartrate to prepare CPL active materials.Details as follows:1.Design and synthesis of cyanostilbene derivatives with R-binaphthol as chiral donor,and then introduce different alkyl chains at the periphery to obtain three CPL materials.The test shows that the lengthening of the alkyl chain has an enhanced effect on the AIE performance of non-liquid crystal materials,while the simple lengthening of the alkyl chain cannot increase the CPL performance.2.The preparation uses cyanostilbene as the AIE molecule,and the AIE molecule is modified by different alkyl chains to make it have liquid crystal properties.Then（1R,2R）-1,2-cyclohexanediamine and AIE are connected in the form of covalent bond to obtain the CPL liquid crystal material.The test shows that the moderate alkyl chain has the best effect on fluorescence enhancement,and the longer the alkyl chain will reduce the phase transition temperature.In addition,the alkyl chain is conducive to the aggregation and stacking of molecules.In the liquid crystal phase state,the alkyl chain can promote the helical stacking of the molecules,thereby enhancing the CPL activity.The self-assembly ability of the alkyl chain is octyl the best.3.A series of CPL liquid crystal materials were constructed with L-（+）-dimethyl tartrate as the chiral donor and cyanostilbene as the luminescent group.The study found that the alkyl chain is octyl with the highest fluorescence intensity,and the liquid crystal properties study showed that the series of molecules were smectic in the liquid crystal phase.CPL studies show that this series of Compounds are excellent CPL active materials.4.By changing the bridging method,it was explored whether CPL materials with ester functional groups could specifically identify substances,and whether the change in the bridging method would affect the AIE and CPL properties of the Compounds.Studies have shown that increasing the ester group cannot make the target Compound have recognition function,and the target Compound can still exhibit excellent AIE performance after the change of bridging mode,and the longer bridging structure will reduce the CPL signal.