Study On The Host-guest Interaction And Application Of Cyclopentyl Citrulline And Nitrogen Heterocyclic Compounds

Cucurbit[n]urils(Q[n]s)belong to the macrocyclic family like crown ethers,cyclodextrins and calixarenes.They have polar ports and hydrophobic cavities,and their structures are highly symmetrical.Since host-guest chemistry is mainly focused on the weak interaction(non-covalent bond),Cucurbit[n]urils has been widely used in host-guest chemistry due to its unique structure.However,the solubility of common Cucurbit[n]urils is poor,which limits the development of research on Cucurbit[n]urils.Therefore,the research and application of Cyclopentanocucurbit[6]uril with excellent solubility can fill this shortcoming.Nitrogen-containing heterocyclic compounds are the basic components of many pesticides and pharmaceutical structures because of their unique high endoscopicity,low toxicity and biological activity.Therefore,this paper takes nitrogen-containing heterocyclic compounds as the guest and Cyclopentanocucurbit[6]uril as the host to study and discuss the hoster-guest interaction between them,then explore their application value in biological science,material science and other fields.1.Six alkyl imidazolium hydrochloride(g1,g2,g3,g4,g5 and g6)were selected as guests,and the interaction between CyP₆Q[6]and the guests in the liquid phase was studied by ¹H NMR,ESI-TOF mass spectrometry and ITC.The experimental results showed that CyP₆Q[6]formed a 1:1 inclusion complex with each of these guests.For CyP₆Q[6]–g1,g1completely enters the cavity of CyP₆Q[6];CyP₆Q[6]–g2,CyP₆Q[6]–g3,CyP₆Q[6]–g4 have a similar mode of interaction,that is,the guest alkyl chain enters the cavity of CyP₆Q[6].The interaction between CyP₆Q[6]and g5 is interesting because the alkyl chain of g5 is bent,allowing the entire guest molecule to enter the cavity of CyP₆Q[6].For CyP₆Q[6]–g6,the imidazolium ring end and part of the alkyl chain of g6 enter into the cavity of CyP₆Q[6]and present a curved state.The crystal structures of g2 and g3 complexes are consistent with the phenomenon in the liquid phase,that is,the alkyl chains of g2 and g3 enter the cavity of CyP₆Q[6].2.A series of benzimidazole compounds(ga,gb,gc,gd,ge,gf and gg)were selected as the guest to study the host-guest interactions between CyP₆Q[6]and ga–gg.The Analysis methods were ¹H NMR,UV-Vis,ITC,ESI-TOF mass spectrometry and single-crystal X-ray diffraction analysis.The results showed that all the seven benzimidazole compounds could interact with CyP₆Q[6]to form a 1:1 inclusion complex.The difference is that the part of the guest entering the cavity of CyP₆Q[6]changes due to the different perssad.In the liquid phase,the benzimidazole of ga is partially encapsulated in the cavity of CyP₆Q[6],while the position of the amino group cannot be determined by ¹H NMR.For gd,ge and gg,the mode of host-guest interactions is similar to that of ga,in that part of the benzimidazole enters the cavity of CyP₆Q[6],but can determine the position of the R perssad(hydroxymethyl,methyl and piperidyl),that is,they are all located outside the port of CyP₆Q[6].There are two modes of interaction between gb and CyP₆Q[6],in which benzimidazole and benzene ring alternately enter the cavity of CyP₆Q[6].Both gc and gf have the same mode of interaction,with R perssad(pyridyl,thiazolyl)encapsulated in the cavity of CyP₆Q[6],and benzimidazole located outside the port of CyP₆Q[6].In solid state,the binding ratio of ga–gg to CyP₆Q[6]was the same as that in liquid state,which was 1:1.In CyP₆Q[6]–ga crystals,part of the benzimidazole can be seen in the cavity of CyP₆Q[6],while the amino group is located in the port of CyP₆Q[6].The obtained CyP₆Q[6]–gb crystal is the first mode of interaction in the liquid state,that is,part of the benzimidazole enters the cavity of CyP₆Q[6]and the benzene ring is located outside the port of CyP₆Q[6].CyP₆Q[6]–gc,CyP₆Q[6]–gd,CyP₆Q[6]–ge,CyP₆Q[6]–gf and CyP₆Q[6]–gg crystal and liquid conditions are the same.3.1,2-bis(4-pyridinyl)vinyl hydrochloride(G)was selected as the object to study the host-guest interaction and application of CyP₆Q[6]with G.The host-guest interaction were characterized by ¹HNMR,UV-Vis,fluorescence emission spectroscopy and ITC.The results showed that CyP₆Q[6]formed a 1:1 inclusion complex with G,and the binding constant was4.028×10⁶L·mol^-1.A fluorescent probe G@CyP₆Q[6]was constructed and its ability to recognize metal cations was studied by fluorescence spectroscopy in aqueous solution.In neutral environment,the probe G@CyP₆Q[6]has high efficiency and specific selectivity to Hg²⁺,and has a strong ability to resist the interference of metal cation.Hg²⁺showed a good linear correlation(R²=0.9911)with the fluorescence intensity of the probe solution at the concentration of 2.0×10^-6-1.0×10^-5mol·L^-1.The detection limit of Hg²⁺is 5.603×10^-9mol·L^-1,which is of great significance for the detection of trace Hg²⁺in water-soluble systems.