Study On The Host-guest Interaction Between Cucurbit[n]urils And Water-soluble Nitrogen-containing Heterocyclic Derivatives

Host-guest chemistry is a discipline that studies supramolecular assemblies based on non-covalent bonds.Cucurbit[n]urils?Q[n]s?is a new member of the large ring family after crown ether,cyclodextrin and Calixarene,playing an increasingly important role in host-guest chemistry because of its highly symmetrical structure,hydrophobic cavity and polar carbonyl oxygen modified port.In this paper,Q[n]s with different degrees of polymerization are used as the host molecules,select or design and synthesize important guest molecules,and study the role of their host and guest to develop potential application values in different fields such as materials science,biological sciences,physics,and information science.In this paper,a series of 4-Pyrrolidinopyridinium derivatives,a series of 1H-Benzotriazole derivatives,a semi-cyanine and acridine hydrochloride were designed and synthesized.Based on these water-soluble azacyclic derivatives,the physical and chemical properties of the host and guest formed by the azacyclic derivatives and Q[n]s were studied by NMR technology,ultraviolet absorption visible spectroscopy,fluorescence emission spectroscopy,isothermal titration calorimetry?ITC?,MALDI-TOF MS and X-single crystal diffraction.The experimental contents and research results are as follows:?1?Designed and synthesized a series of 4-Pyrrolidinopyridinium derivatives?g1,g2,g3,g4,g5,g6?,Q[8]was selected for host-guest supramolecular self-assembly,by NMR technology,ultraviolet absorption visible spectroscopy,ITC,MALDI-TOF MS,and X-ray single crystal diffraction method were studied with the interactions between the host molecular Q[8].The experimental results show that:For g1,the guest?except for the alkyl chain?is wrapped in the cavity of Q[8];For g2 and g3,Q[8]is in a dynamic equilibrium with the inclusion mode of the guest;For g4,g5 and g6,except pyrrole ring,the rest of the guest is encapsulated in Q[8]cavity.In the solid state,the structure is somewhat different:in the crystal of Q[8]@g2,a pair of guest molecules with central symmetry are bound in the cavity of Q[8],the guest molecules enter the cavity of Q[8]at a rather shallow angle,and the alkyl chain is exposed at the port of Q[8];Interestingly,for Q[8]@g3,there are two crystal configurations,one of which is similar to the Q[8]@g2 crystal,while for the other,four carbon atoms of the alkyl chain of the guest enter the Q[8]cavity and are almost perpendicular to the plane of the Q[8]carbonyl oxygen.?2?The same guest molecules mentioned above,4-?C₄H₈N?C₅H₅NRBr,where R=ethyl?g1?,n-butyl?g2?,n-amyl?g3?,n-hexyl?g4?,n-octyl?g5?,and n-dodecyl?g6?,were used to investigate their interactions with the host and guest of Q[10]through spectral study.The results show that the guest g1-g5 is completely located in the cavity of Q[10],in which the alkyl chains of g4 and g5 may be bent in the cavity of Q[10],in addition,due to the large cavity of Q[10],the inclusion of the guest and Q[10]may also be in dynamic equilibrium.For g6,the pyrrole ring portion is located outside port of Q[10].DFT quantization shows that the guest is stable in Q[10],and the curvature of alkyl chain increases with the increase of chain length.?3?A series of 1H-Benzotriazole derivatives?CBTC2,CBTC3,CBTC4,CBTC5,CBTC6,CBTC7,CBTC8,CBTCB?were designed and synthesized,and Q[8]was selected to perform supramolecular self-assembly with them.The results of spectral studies show that for these eight objects,the interaction ratio between them and Q[8]is 1:1 by ultraviolet absorption visible spectrum,fluorescence emission spectrum,ITC and MALDI-TOF MS.It can be seen from¹H NMR titration data that,,for the 7 kinds of guest,CBTC2-CBTC8,the alkyl chain where the carboxyl group is located slowly moves out of the Q[8]cavity with the increase of the length of the alkyl chain of the guest molecule.For CBTCB,due to the presence of benzyl,the benzene ring of 1H-Benzotriazole is extruded from the Q[8]cavity,and the alkyl chain of carboxylic acid and benzyl are in the Q[8]cavity.?4?A hemiocyanine indoles derivative H was designed and synthesized.Based on this semi-cyanine,the competitive effects of host and guest between Q[7]and Q[8]were studied.It is found that when the Q[n]is one equivalent,the Q[n]preferably contains 4-NMe2-phenyl and ethylene ligands.However,if the second equivalent Q[n]is added,when n=8,the situation is reversed,Q[8]will give priority to the quaternary ammonium salt motif of the inclusion guest;When n=7,the use of excessive Q[7]has no effect on 1:1 inclusion.Subsequently,based on the guaest H,a study was conducted on the competition between the host and guest of the Q[7]and Q[8],and it was found that the binding capacity of Q[8]with guest molecules was greater than Q[7].?5?A water-soluble acridine derivative?AC?was obtained by protonizing acridine with hydrochloric acid.Choose Q[8]and conduct a study on the role of host and guest.The results show that in aqueous solution,AC can be encapsulated in Q[8]cavity to form 1:2 host and guest complex.Q[8]-AC fluorescence probe for amino acid detection was constructed because the free AC had strong fluorescence,which was quenched in the inclusion compound of Q[8]-AC.It was found that due to the competitive interaction between L-phe or L-trp,this non-fluorescent Q[8]-AC complex was used as a fluorescent"off"probe to identify L-phe or L-trp.Basic L-amino acids?L-Arg,L-His or L-Lys?were identified by the p H response of Q[8]-AC system.