Study On Host-guest Assembly Based On Water-soluble Pillar[5]arene And Cucurbitaci

Supramolecular chemistry focuses on molecular recognition and the formation of higher-order assemblies through non-covalent interactions.Macrocycle chemistry plays an important role in supramolecular chemistry,and macrocycles are versatile building blocks for supramolecular design.In the history of macrocyclic chemistry,supramolecular scientists have explored and studied crown ethers,cyclodextrins,calixarenes and cucurbit[n]urils,four generations of classic macrocyclic molecules,and a new generation of macrocyclic host molecules,Pillar[n]arenes.In this dissertation,a series of host-guest assemblies are mainly constructed with water-soluble pillar[5]arenes and cucurbit rings with different degrees of polymerization as the main body,and their applications in analytical detection and photochemical reactions are studied.The experimental content and results are as follows:（1）A new water-soluble all-aminopyridine pillar[5]arene ApP5 was designed and synthesized,and its structure was characterized by means of nuclear magnetic resonance spectroscopy and X-ray diffraction of single crystal.In addition,the selective recognition of anions by ApP5 was also investigated.ApP5,as a macrocyclic fluorescent probe,showed a sharp increase in fluorescence in THF/H₂O（90/10,v/v）solution due to aggregation-induced emission（AIE）effect.Whereas,after the addition of I^-,the fluorescence of ApP5 was quenched.The method presented in this study provides a new method for the selective detection of I^-in solution.（2）The host-guest interaction between pillar[5]arene and 3-hydroxy-2-naphthoic acid（HNA）was studied by fluorescence and nuclear magnetic resonance spectroscopy.The results showed that ApP5 formed a 1:1 host-guest complex with3-hydroxy-2-naphthoic acid,ApP5@HNA.Using the fluorescence properties of the host-guest inclusion complex,20 metal ions in water were detected one by one,a nd the results showed that Fe³⁺can quench the fluorescence.Therefore,the complex ApP5@HNA can be used as a fluorescent sensor to detect Fe³⁺.（3）A fluorescent molecule（E）-1-（2-hydroxyethyl）-4-（4-hydroxystyryl）pyridin-1-ium bromide（HPy）was designed and synthesized,and the host-guest interaction between HPy and cucurbit[8]uril（Q[8]）was studied by nuclear magnetic resonance spectroscopy,fluorescence spectroscopy,ultraviolet-visible spectroscopy and mass spectrometry.The results showed that HPy and Q[8]formed a 2:1supramolecular complex HPy₂@Q[8]through host-guest assembly.The encapsulation of Q[8]resulted in the quenching of the fluorescence emission of HPy molecules.However,among many pesticides,only the addition of tricyclazole can effectively turn on the fluorescence,so this system can be used to detect the pesticide tricyclazole,showing excellent selectivity and high sensitivity.In addition,nuclear magnetic resonance spectroscopy,mass spectrometry,semi-empirical calculation models and other means have proved that the formation of ternary complexes is the reason for the turn-on of fluorescence.（4）The photosensitive molecule CHP was designed and synthesized,and the host-guest interactions between CHP and cucurbit[n]urils with different cavity sizes（TMe Q[6],Q[7]and Q[8]）were investigated,respectively.The results show that CHP forms supramolecular complexes with n _Q[n]/n _CHP=1:1,2:1 and 1:2 with TMe Q[6],Q[7]and Q[8],respectively.Due to the good photosensitivity of CHP,the C=C bond of CHP undergoes cis-trans isomerization and[2+2]cycloaddition reaction in aqueous solution under 365 nm UV light irradiation.After combining with TMe Q[6],TMe Q[6]shuttles on the CHP molecular axis due to the isomerization of C=C under365 nm UV light irradiation.After binding with Q[8],the photo-induced[2+2]cycloaddition reaction rate of the CHP is greatly increased,while after binding with Q[7],the C=C bond of the CHP only undergoes a cis-trans isomerization reaction,i.e.no further photo-induced[2+2]cycloaddition reaction occurs.Competitive experiments demonstrated that CHP is more inclined to combine with Q[7],and thus,when Q[7]and Q[8]coexist in the system,the inhibition of the[2+2]cycloaddition reaction of CHP by Q[7]is not disrupted.The characteristics of this supramolecular catalysis and supramolecular protection make it applicable to catalyze or inhibit reactions required under specific circumstances.