Studies On Preparation And Aggregation-Induced-Emission Property Of M_nL_2nMetal-Organic Cages Based On Tetraphenylethylene

Self-assembly is an effective method to create materials and endow the system new functions.However,how to monitor this process so as to control the function of the assembly is a challenge in scientific research.Fluorescence spectroscopy has the advantages of high sensitivity and low limit of detection.The introduction of fluorescent groups into the assembly precursor and the use of Aggregation-Induced-Emission(AIE)effect are expected to solve this problem.Up to now,investigations based on AIE mainly focused on the locking of the AIEgenes,in which modification of fluorescent guest molecules are required,making the preparation much complicated and tedious.By coordination of specific metal ions,the bipydine-based ligands can form regular 3D cages,which can be applied widely in the fields of drug deliveries,molecular catalysis,sensors and preparation of materials,due to their unique cavities.Based on the confinement effect of metal-organic-cages,it is expected to realize the monitoring of the assembly process by skillfully introducing the fluorophore during the formation of the assembly,which leads to the Aggregation-Induced-Emission.In this thesis,two types of AIEgene-based ligands with different angles were synthesized and further formed M_nL_2n-type metal-organic-cage(MOC)through coordination,according to the idea of"confinement effect".The MOC and fluorescent property were characterized.Furthermore,pillararene-containing bifunctional ligand was designed and synthesized,and further formed MOC.The fluorescence emission was enhanced by combination of AIE with host-guest interaction.The main content was as follows:Charpter 1:IntroductionIn this part,the metal organic cage(MOC),especially the development of M_nL_2nMOC was described in detail.Then,strategies of controllable self-assembly of MOC were classified and described.Then,the research progress of functionalization of MOC,including internal and external functionalizations,as well as the construction and application of multi-component MOC were discussed in detail with examples.The luminescence mechanism of AIE was described briefly.Finally,the significance of this thesis was presented and plan of this research was proposed.Charpter 2:Preparation and aggregation-induced-emission property of the"light-up"M₁₂L₂₄ metal-organic cage triggered by confinementIn this study,the convenience of using metal organic cages as the framework for the study of confinement effects was firstly described,followed by the achievement of application of confinement effect in catalysis research.Based on the literatures,we proposed the following design.The tetraphenylethylene-containing ligand L₁ with the angle of 120°was synthesized,which formed metal organic cages through coordination with the salt Pt(CH₃CN)₄(OTf)₂.The structure of MOC was characterized by NMR,MS and DLS.Finally,the photophysical properties of MOC were characterized by UV-vis and FLS.Charpter 3:Preparation and aggregation-induced-emission property of the tetraphenylethylene functionalized M₂L₄metal-organic cagesIn this part,based on the design principle of confinement effect and result of the second part,M₂L₄metal-organic-cage was designed.The tetraphenylethylene-containing ligand L₂with the angle of 180°was synthesized.The products obtained in each step were characterized by NMR or MS.Subsequently,three transition metal ions Pd(II),Pt(II)and Zn(II)with a planar square structure were chosen to coordinate with the ligand L₂,and subsequently self-assemble into M₂L₄metal-organic cage under the drive of a suitable solvent.The structure of MOC was characterized by NMR,MS and DLS.Then,the photophysical properties of MOC were characterized by UV-vis and FLS.In addition,molecular simulation was carried out to verify the experimental results.Charpter 4:Preparation of bifunctional M₁₂L₂₄ metal organic cage and construction of the supramolecular platformIn this part,based on the previous results,both pillararene and tetraphenylethylene-containing ligand L₃with the angle of 120°was designed and synthesized,inspired by the idea of host-guest complexation and step-by-step self-assembly.The products of each step were characterized by means of NMR.The ligand could coordinate with Pt(CH₃CN)₄(OTf)₂and self-assemble to obtain a MOC Pt₁₂(L₃)₂₄.The structure was characterized by NMR and ESI-TOF-MS,and verified by PM₆ molecular simulation.The morphology was characterized by AFM.As demonstrated by NMR,AFM and DLS,this MOC exhibited the ability to recognize guest molecules.Host-guest interaction and coordination had a synergistic effect on the AIE property of MOC,demonstrated by UV absorption and fluorescence spectroscopy.