Study On The Construction And Performance Of Supramolecular System Of Spiral Fourteen-membered Cucurbital Ring And Aromatic Ring Compounds

In the supramolecular host-guest chemistry,as an artificial macrocyclic acceptor,cucurbit[n]urils（Q[n]s）has a hydrophobic cavity with two opening portals rimmed with identical carbonyl groups,and can selectively accommodate guest molecules with suitable shapes and sizes.Therefore,the host-guest interaction of cucurbit[n]urils exhibits a unique Q[n]-based host-guest chemistry compared to cyclodextrin,calixarene,etc..Twisted cucurbit[14]uril（tQ[14]）,a new member in the cucurbit[n]uril family,was first reported by our research group in 2013,it is constructed of two helixes,inside and outside,which are opposite in the direction of the helix.Therefore,the tQ[14] molecule has two kinds of cavities（a central cavity and two side cavities）and shows many special properties and new application.In this thesis,tQ[14] as selected as the host,p-diaminoazobenzene（DAAB）,thioflavin T（ThT）,2-[4-（dimethylamino）styryl]-1-methylpyridinium iodide（DASMPI）,were selected as guests.Based on the interaction of tQ[14] with three guests,respectively,supramolecular systems of aromatic guests@tQ[14] sensors were constructed,and their recognition performances for various ions（cations or anions）were investigated.It could provide useful ideas and methods for the further application of tQ[14].The main research contents and results are as follows:The host-guest interaction between DAAB and tQ[14] in an aqueous HCl solution（p H=3）was studied by nuclear magnetic resonance spectroscopy and UV-visible absorption spectrophotometry,and the experimental results reavled that the opening shell structure of tQ[14] can induce trans-DAAB to become cis-DAAB and form the cis-DAAB@tQ[14] inclusion complex at room temperature,whereas the temperature-stimulated the cis-DAAB@tQ[14] supramolecular system disociated to yield tQ[14] and trans-DAAB.The response of the cis-DAAB@tQ[14] supramolecular system for a series of common anions shows that the cis-DAAB@tQ[14] supramolecular system can selectively recognize Ac O-and Fwith the detection limits of 5.17×10-5 mol/L and 1.84×10-4 mol/L,respectively.The host-guest interactions between ThT and t Q [14] were investigated by ¹H NMR,2D NMR,DOSY,spectroscopic（UV/Vis absorption and fluorescence）spectroscopy,isothermal calorimetry,and dynamic light scattering;Most of the cavities in the electrostatic potential calculation tQ[14] are in the electron-negativity region,which may cause the guest to enter the cavity of the tQ[14] and experience deshielding microenvironments.The interaction with tQ[14] enhances the fluorescence of ThT in aqueous solution.Indeed,the fluorescence intensity of ThT increases rapidly with increasing amount of tQ[14] up to a tQ[14]:ThT ratio of 15.Interestingly,at lower tQ[14]:ThT ratios（1:1）,the introduction of alkaline earth metal cations(AE²⁺)into the tQ[14]–ThT interaction system leads to fluorescence quenching of ThT,except in the case of Mg²⁺ cation,which leads to an initial fluorescence enhancement followed by a gradual quenching of ThT.At higher tQ[14]:ThT ratios（15:1）,the introduction of alkaline earth metal cations into the tQ[14]-ThT interaction system leads to the precipitation of solid tQ[14]/ThT/AE²⁺ interaction products,which emit strong blue fluorescence,except in the case of Sr²⁺ cation,which gives fluorescence quenching of ThT without any solid precipitation.Thus,the tQ[14]–ThT interaction system shows potential applications not only for preparing stimuli-responsive supramolecular photoluminescent materials,but also for identifying Mg²⁺ at lower tQ[14]:ThT ratio and Sr²⁺ at higher tQ[14]:ThT ratio,respectively.Finally,the host-guest interactions between DASMPI and tQ[14] were investigated by ¹H NMR,2D NMR spectroscopy（UV/Vis absorption and fluorescence spectroscopy）and isothermal calorimetric titration;the study showed that DASMPI can form a 1:1 host-guest complex with tQ[14].Based on the special structure and properties of tQ[14],different proportions of tQ[14] and DASMPI supramolecular systems were constructed.When the ratio of tQ[14] to DASMPI is 1:1,alkali metal ions have a competitive or synergistic effect on the original mode of action of the tQ[14]/DASMPI（1:1）supramolecular system.When the ratio of tQ[14] to DASMPI is 15:1,the alkali metal ions（Li⁺,Na⁺,K⁺）will give a yellow solid fluorescence to the tQ[14]/DASMPI（15:1）supramolecular system;for Rb⁺,Cs⁺ does not precipitate the tQ[14]/DASMPI（15:1）supramolecular system.