| Circularly polarized luminescence(CPL)reflects the properties of the excited states of chiral materials,which has been attracting increasing attention as a result of its particular properties in all fields.For instance,3D optical displays,information storage and processing,molecular switches,biological detection and probing.Up to now,different CPL systems have been reported.As we all know,aggregation induced fluorescence quenching(ACQ)is a common phenomenon in solid-state organic light-emitting materials,which limits the application of traditional fluorescent materials.Therefore,the synthesis of circularly polarized luminescence(CPL)based on the aggregation-induced emission(AIE)provides an approach to prepare CPL materials with high emission intensity in the solid state.In addition,based on the basic principle of this multifunctional molecular design,it is of great significance to design molecular systems that can regulate the properties of CPL.In this dissertation,several kinds of AIE-active CPL materials were designed and synthesized.In order to achieve high glum value,the relationship between the properties of aggregation-induced circularly polarized luminescence(AI-CPL)and its microstructure wasinvestigated by molecular modification and environmental modification.The main works of this dissertation are as follows:1.We used the classic AIE-active fluorophoretetraphenylethene(TPE)as the luminescent skeleton,chiral glutamic acid or L-aspartic acid derivatives as the chiral source.Three chiral AIE-active luminogens L-Glu-TPE,D-Glu-TPE and L-Asp-TPE were prepared,which couldself-assemble into organic gels.The relationship between the properties of aggregation-induced circularly polarized luminescence(AI-CPL)and its microstructure was investigated by changing the ratio of tetrahydrofuran and toluene.All of these compounds can exhibit tunable AI-CPL properties which show very weak emission and CPL signals in solution state,but pruduce strong emission and regulated CPL intensity in the gel state.Furthermore,the SEM images showed that the change of morphology of chiral supramolecular microstructure could result intunable AI-CPL properties.2.Four chiral AIE-active luminogens(AIEgens)containing tetraphenylethene(TPE)and one or two chiral glutamic moieties connected by thiourea were designed and synthesized.All AIEgens showed tunable aggregation-induced circularly polarized luminescence(AI-CPL)by adjusting the mono-/di-substituents of molecules or nanostructures of self-assemblies.The enantiotopic mono-substituted compounds(TPE-Glu)exhibited mirror-imaged AI-CPL signals with the maximal |gium| value of up to 0.02.Interestingly,the di-substituted cis-and trans-isomers showed reverse AI-CPL signals compared with those of monosubstituted ones.cis-and trans-isomers(TPE-DGlu)showed similar AI-CPL properties,whose signs of AI-CPL signals reversed while the water fraction(fw)was more than 80%.The SEM images of their aggregates indicated that the AI-CPL properties should have an intrinsic relation with their molecular structures or self-assembled nanostructures.3.Three compounds R-BBT-1,R-BBT-2 and R-BBT-3 were designed and synthesized based on R/S-BBT.The relationship between AI-CPL properties and microstructure were analysised by changing the ratio of different THF and water.All four compounds exhibit obvious AIE activity,CD and CPL signals.Interestingly,the signals of CD and CPL of R-BBT reversed while the water fraction was at 81%,and the intensity of CPL increased sharply with the maximal |glum| value up to 0.09 at 640 nm.However,the enantiotopic mono-substituted compounds S-BBT and compounds R-BBT-1,R-BBT-2 and R-BBT-3 with alkyl chains at different positions showed no significant change under the same conditions,which indicates that the optical activity of compound R-BBT at 81%fw depends on its own structure.In addition,the results of SEM images show that AI-CPL properties should have an intrinsic relation with their molecular structures. |
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