Synthesis Of Trans-cucurbits And Their Molecular Recognition Properties

The cucurbit[n]urils is a new type of the highly symmetric barrel macrocyclic molecular compound.The improment of synthesis and separation methods lead to appearance of a series of cucurbit[n]uril derivatives with novel structures and properties,such as the inverted cucurbit[6]uril and inverted cucurbit[7]uril(iQ[6] and iQ[7]).However,the difficulties associated with separating iQ[n]s appears to have hindered investigation of iQ[n] chemistry since no further reports in this area have been made.The host-guest chemistry,as the core research project of the cucurbiturils chemistry,there have been quite a few studies focusing on supramolecular assemblies of Q[n]s themselves in recent years.Combination of literature works and the experimental result,the construction of supramolecular assemblies between cucurbit[n]urils and the Linear and dendritic molecules have become the main contents in this thesis.In this paper,we studied the interaction between 4,4’-bipyridyl derivatives,essential amino acid molecules,hemicyanine dyes and inverted cucurbit[7]uril;constructed the hyperbranched supramolecular polymer from twisted cu curbit[14]uril and porphyrin based on host–guest interactions.The properties of the self-assembled system were studied by single-crystal X-ray diffraction analysis,nuclear magnetic resonance(NMR),isothermal thermal titration(ITC),UV absorption spectr oscopy,fluorescence spectroscopy and mass spectrometry(MS).The experimental results showed that:(1)the aromatic nuclei of BPY2+,MV2+ and EV2+ were partially encapsulated into the iQ[7] host,giving rise to 1 : 1 binary inclusion complexes;with the longer chain viologens(PV2+,BV2+,FV2+,HV2+ and SV2+),only the alkyl chains were embedded in the cavity of the iQ[7] host,forming 2 : 1 ternary complexes.(2)The experimental results indicated strong binding with the aromatic amino acids Trp and Phe.Lys,Arg and His guests lie outside the host’s portal,whereas the alkyl moiety of Met,Leu and Ile guests were accommodated within the iQ[7] cavity.At pD=3,the side chains of basic amino acids were located in the cavity of iQ[7] in acidic conditions.The aromatic amino acids Trp and Phe were more deeply buried in the iQ[7] cavity.(3)A large fluorescence enhancement of DSMI was realized by the formation of an inclusion complex with iQ[7].A nice 1 : 1 inclusion complex was determined.We also devised a method for the controlled release of the DASPMI from the iQ[7] macrocycle by adding α,α’-diamino-p-xylene.(4)A novel supramolecular polymer was successfully constructed between cucurbit[14]uril and 5,10,15,20-tetrakis(N-butyl-4-pyridinium)porphyrin tetrabromide depending on the host–guest interactions.Nevertheless,addition of the competitive guest compound KCl led to effective dissociation of the supramolecular polymer Q[14]-TBPyP and re-formation of the original guest species,giving additional support for the host–guest interaction-based supramolecular polymer nature of the present system.