| Fluorescent functional materials have attracted remarkable attention due to their significant applications and promising potentials in the fields such as fluorescent probes,bioimaging,photoelectronic devices,molecular sensing and data detection.However,the fabrication and application of fluorescent materials were largely limited because the traditional fluorescent dyes always exhibited aggregation-caused quenching(ACQ),resulted from the intermolecular ?-? stacking in aggregated states.In 2001,Tang and co-workers reported the aggregation-induced emission(AIE)phenomenon.The typical AIE molecules,such as tetraphenylethylene(TPE)and 9,10-distyrylanthracene(DSA),possess unique chemical structures like propeller,causing the fluorescent enhancement resulted from the restriction of intramolecular phenyl rotation.The development of AIE molecules has broken the limitation of ACQ,paving a new way to fabricate the fluorenscent functional materials,especially the solid-state fluorescent materials.Compared with traditional polymeric materials,supramolecular functional materials exhibited stimuli-responsive to the external environment and specific recognitions towards typical moleculars,because their fabrication is based on the supramolecular force.Much efforts have been devoted to construct advanced supramolecular materials in the past decades,since they have great significance in the areas of biological science and material science.As the important building blocks of supramolecular materials,the design and syntheses of synthetic macrocycles is the foundation for the developments and progress of supramolecular chemistry.As a new class of synthetic macrocycles,pillar[n]arenes possess rigid structures,unique host-guest properties and facile functionalization.Supramolecular materials fabricated from pillar[n]arenes and their derivatives have been extensively utilized in the areas of biology and material sceience.In this thesis,we combined the AIE mechanism and pillar[n]arene-based supramolecularapproach and proposed the concept of supramolecular-assembly induced emission enhancement(SAIEE).A series of pillar[5]arene derivatives with fluorescence have been designed and synthesized,bridged by TPE or DSA cores.Fluorescence-enhanced supramolecular systems with stimuli-responsiveness and fluorescence-tunable supramolecular materials with stimuli-responsiveness were constructed from pillar[n]arene-based host-guest assemblies.The projects in this thesis are significant for the diversity of pillar[n]arenes,and paving a new approach to develop novel fluorescent materials and achieve the tunable fluorescent colors of materials.There are four parts in this thesis as following:Firstly,we successfully synthesized the DSA-bridged pillar[5]arene dimers,which can be fabricated into supramolecular linear polymers with yellow emission through assembling with a guest linkers via host-guest interactions.Upon the addition of the assembled degree,its fluorescent emission intensity increased gradually.Furthermore,we designed and synthesized a TPE-bridged pillar[5]arene tetramer(H1),which can be fabricated into A4/B2-type supramolecular polymer NG2?H1,exhibiting strong blue fluorescent emission due to SAIEE.Resulting from the weak force of host-guest interactions,NG2?H1 exhibited dual-responsive properties towards temperature and solvents.Significantly,NG2?H1 finally turned into supramolecular gel with blue emission when the concentration was higher enough.Meanwhile,the pre-organized NG2?H1 gel showed different morphologies including polygons and membrane,all of whose blue emission could be detected under fluorescent microscopy.Secondly,The guest molecule with two binding sites,i.e.,DSA-G was designed and synthesized.Two supramolecular assemblies i.e.,DSA-G?H1-4C4 P and DSA-G?H2-2C4 P systems were constructed from DSA-G and two TPE-bridged pillararene tetramers.Under the cooperative effects of SAIEE and F?rster Resonance Energy Transfer(FRET)process,the controlled change of fluorescent colors can be achieved by adjusting the molar ratio of hosts and guests.Thirdly,we constructed four supramolecular ensembles,i.e.,SG?SH,LG?SH,SG?LH and LG?LH from two AIE-active pillar[5]arene tetramers(SH and LH)and two guest linkers(SG and LG)with different length of carbon chains.All of them exhibited fluorescent emission enhancement upon the addition of guest molecules.SG?SH showed the largest fluorescent enhancement due to the shorter carbon chains.However,only LG?LH can finally turn into supramolecular gel with blue emission,because the longer carbon chains endowed them with more flexibility and extensibility,while gel couldn't be constructed from SG?SH because the rigid structures and steric hindrance.This study reminds us to consider the flexibility of the building blocks when fabricating the supramolecular gels.Forthly,inspired by RIR mechanism,we designed and synthesized a novel fluorescent pillar[5]arene dimer(FH),which exhibited remarkably strong blue emission in their aggregated states.The quantum yields of FH in solution is 46%,while its quantum yields increased to 75.5% in the solid state,exhibiting AIE property.However,the corresponding monomer of FH,i.e.,FM has the quantum yields below 20% both in solution and solid state,and the fluorescent intensity in solid state was lower than that in solution.We found that pillar[5]arene groups in FH provided large steric hindrance and the molecular stacking as driven by the multiple C-H......? interactions,resulting in the restriction of phenyl rotation,and finally causing the fluorescent enhancement.DSA or BODIPY derived guest molecules were also synthesized and the fluorescent supramolecular ensembles,DG1?FH,DG2?FH and BG3?FH,were fabricated.White-light emitting was achieved when DG2?FH was in toluene solvent. |
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