Construction And Application Of Fluorescent Materials Based On The Host-Guest Interaction Between Cucurbit[n]uril And Azapyrene Derivatives

Fluorescent functional materials are one of the hotspots in the field of materials,due to their important application in the fields of optoelectronic devices,data storage and encryption,biological imaging and therapy.However,traditional fluorescent dye molecules undergo fluorescence quenching due to π-π stacking in the aggregate state,which limits the development and application of fluorescent materials in a way.In recent years,with the quick development of supramolecular chemistry,studies on the use of supramolecular host-guest interactions to change the stacking mode of fluorescent molecules and regulate their fluorescence emission have emerged one after another.At the same time,the assembly constructed by the host-guest interaction can realize multicolor luminescence including white light emission.Cucurbit[n]uril(CB[n],n=5-8,10,13-15)as the fourth-generation macrocyclic host has aroused great interest of chemists.The unique rigid structure and hydrophobic cavity of CB[n]make it a promising prospects in the field of supramolecular chemistry.In this thesis,the fluorescent acceptor 2,7-azapyrene was used as the building unit,few guest compounds with D-A and A-D-A structures and amphiphilic aggregation-induced emission(AIE)derivatives were synthesized,and their binding/assembly behaviors with CB[n]were investigated.On this basis,we further explored the effects of the host-guest interaction of cucurbit[n]uril on the aggregation state,intermolecular interactions and assembly properties of different guests.The thesis mainly includes the following three parts:1.Four conjugated D-A structures and three unconjugated A-D-A structure guest molecules were designed and synthesized,and the host-guest bindings between them and CB[8]/CB[10]were studied by NMR,mass spectrometry and UV/fluorescence spectroscopies.The results showed that CB[8]can form 1:1 host-guest inclusion complexs with the guest Ⅱ-G2,Ⅱ-G3,Ⅱ-G4,and Ⅱ-G5,respectively.With the addition of various amount of CB[10],the fluorescence color of guest Ⅱ-G3 continuously changed from the blue-white area to the orange area.When 0.3 equivalent of CB[10]was added,white light color emission of the guest was achieved,owing to the host-stabilized intermolecular charge transfer interactions.In addition,investigations disclosed that CB[8]can form 2:1 host-guest inclusion complexes with the guest Ⅱ-G6,Ⅱ-G7,and ⅡG8,respectively.And CB[10]can bind with the guest Ⅱ-G6,Ⅱ-G7 to form 2:1 and 2:2 host-guest inclusion complexes.Moreover,CB[8]forms a 2:1 host-guest inclusion complex with guest Ⅱ-b-8,limiting the rotation of the tetraphenyl ethylene part and enhancing the fluorescence intensity of guest Ⅱ-b-8 by 4 times in aqueous solution.2.Three conjugated A-D-A structure guest molecules Ⅲ-G1,Ⅲ-G2,Ⅲ-G3 were designed and synthesized.The host-guest bindings and photophysical properties between them and CB[8]/CB[10]were studied by NMR,mass spectrometry,UV/fluorescence spectroscopies and transient spectroscopy.The results of NMR and mass spectrometry indicate that CB[8]can form 2:1 inclusion complexes with the guest Ⅲ-G1,Ⅲ-G2,ⅢG3.Fluorescence titration experiments show that with the addition of CB[8],emission peaks of guests Ⅲ-G1 and Ⅲ-G2 representing the intramolecular charge transfer interactions gradually increased.For guest Ⅲ-G1,the emission color in the aqueous solution changed from nearly white light to the yellow light.When 0.2 equivalent of CB[8]was added,the color of the solution was close to the white light emission.For guest IIIG2,the emission color in the aqueous solution changed from light blue to the yellow light color.When 0.9 equivalent of CB[8]was added,the color of the solution was close to the white light emission.Our results further prove that the host-guest interaction can affect the emission of fluorescent molecules,and the emission color of fluorescent molecules can be tuned by adding vatious amounts of the host.3.The supramolecular assembly light-harvesting system through CB[10]-based host-guest interaction with sequential energy transfer was used to aqueous photochemical catalysis.The CB[10]-mediated hetero-guest amphiphilic assembly and energy transfer process have been studied by transmission electron microscopy(TEM),dynamic light scattering(DLS),fluorescence spectroscopy and transient spectroscopy.CB[10]mediated hetero-guest ternary inclusion complex self-assembled into CB[10]-DAPPY(CB[10]·Ⅳ-G1·Ⅳ-G2)amphiphilic multilayer vesicle in the water phase,compared to the free Ⅳ-G1,showing a significant AIE effect and a significantly enhanced fluorescence luminescence performance.When the hydrophobic fluorescent dye Eosin Y(ESY)and hydrophilic fluorescent dye Rhodamine B were loaded,the donor(CB[10]DAPPY)undergo an efficient sequential fluorescence resonance energy transfer process with acceptors(ESY/RhB).By properly tuning the ratio between the donor and acceptors,bright white light emission successfully achieved.More importantly,to better mimic the natural photosynthesis and take full advantage of the harvested energy,the CB[10]DAPPY-ESY-RhB system can be utilized as a nanoreactor,where photocatalysed crosscoupling hydrogen evolution reaction can be realized with 74%yield in aqueous medium.