Supramolecular Networks Constructed by AIEE-active Pillararene-based Polymeric Hosts:AIEE/Size Tunable Nanospheres and Efficient Light-Harvesting Materials
Author:Xu Lin Xian
Supervisor:cao de zuo
Supramolecular chemistry is an important branch of the chemical science field,exploring the behavior of host and object through weak interactions between two or more molecules.Macrocyclic host molecules with cavities/holes play an essential role in supramolecular chemistry.It can be said that the development of supramolecular chemistry is accompanied by the development of this macrocyclic host molecule.After 50 years of development,with the studies of the classic macrocyclic molecules of crown ether/hole ether,cyclodextrin,calixarene and cucurbituril,the research on supramolecular chemistry has been deepened,and the basic research on the host-guest behavior has been extended to the research on the application of supramolecular complexes.Supramolecular materials has gradually become an interdisciplinary subject.As a fifth-generation macrocyclic host molecule,pillar[n]arene has been a star in the field of supramolecular chemistry since its discovery in 2008.Due to its highly symmetrical cavity structure and excellent host-guest interaction ability,as well as its easy functional modification,it has been widely used in drug loading and release,light-harvesting system,stimulus response,molecular recognition,bioimaging,etc.The works in this article intend to further functionalize the pillar[n]arene,design and synthesize a series of novel pillar[n]arene-based polymeric hosts,meanwhile introduce the AIEE signal into the polymeric host,which can embody the formation of supramolecular self-assembled aggregate structures via host-guest interactions,to get pillar[n]arene polymeric hosts with AIEE properties.The supramolecular self-assembly process is explored by high sensitivity,convenient,easyobservable fluorescence detection methods,and new supramolecular optical materials based on pillar[n]arene were designed and prepared.(1)A novel linear polymer P1,with pillararene and tetraphenylethylene(TPE)units in the backbone,and a series of multi-branched guests containing cyano-triazole sites were designed and synthesized.GMs(containing: ditopic guest G2 and tritopic guests G3-1 and G3-2).Through the self-assembly of P1 and GMs supramolecules,a supramolecular nanosphere system based on supramolecular polymeric host with AIEE-tunable and self-assembled particle size tunable properties was successfully prepared.We named it PASS(Polymeric AIEE-tunable and Size-tunable Suprasphere)system.The particle size and AIEE characteristics of PASS selfassembled nanospheres can be controlled simultaneously in two dimensions: by changing the structure of the GMs and changing the concentration of host P1.The diameter of the PASS nanospheres can be finely tuned from tens of nanometers to hundreds of nanometers without using any template molecules.The study of host-guest binding isotherms shows that the optical and structural properties(fluorescence ability,density and particle size)of PASS are related to the relative fluorescence quantum yield(37),but independent to the host-guest binding constant K.The PASS self-assembling supraspheres can be dissociated by adding a competitive guests,resulting in the quenching of AIEE.This phenomenon was used to detect the interaction between adiponitrile and the P1 system,as a proof of principle.(2)Efficient transfer of energy from donor to acceptor is an important goal for the successful construction of artificial light-harvesting system(ALHS).In this work,a new type of Conjugated Polymeric Supramolecular Network(CPSN)has been prepared and reported as ALHS.With donor/acceptor at 1000:1,CPSN showed the highest antenna effect reported up to now,which can reach 35.9 in solution and 90.4 in film state.For the first time,CPSN selfassembly prepared from a cleverly designed pillararene-based conjugated polymeric host P4 and a series of conjugated guests.P4 has a signal amplification effect as a molecular line due to its conjugated polymer chain with aggregation-induced fluorescence enhancement(AIEE)group in the backbone.It also guarantees efficient energy transfer in the presence of trace receptors(donor/acceptor is 10000:1).In addition,due to the ultra-high antenna effect of CPSN,it is very sensitive to receptor detection with a detection limit as low as 0.24 nM.Therefore,CPSN is expected to become a new multifunctional material such as high-efficiency ALHS and ultra-high sensitivity fluorescent probe.(3)Based on the efficient light-harvesting capability of CPSN,we designed and synthesized a double-branched conjugated guest GB with blue light emission.Together with the other two yellow and red conjugated guests,GB self-assembles with the conjugated polymeric host P4 to form the CPSN system.In this system,there are two different energy transfer processes: poor energy transfer from blue emission guest GB to P4,and good energy transfer processed from the host P4 to the yellow light guest and the red light guest(GY,GR).With different acceptor molecules and different donor/acceptor ratios,CPSN can achieve precise emission modulation with a gamut area of approximately 96% sRGB color gamut area,including pure white emission(0.33,0.33).CPSN is expected to be an efficient wide color gamut luminescent material.In the study we also found that the conjugated structure of CPSN acts as an effective energy transfer bridge.In the GB-P4-GR three-component system,the FRET process from the blue guest GB,which does not fit the FRET condition to the red light guest GR can be clearly observed.