Purification Of Cucurbit[10]uril And Its Cooperative Recognition Research With Macrocyclic Host

Supramolecular chemistry is the study of the supermolecule system with specific structures and functions by the association of two or more chemical species through intermolecular interactions.As we all know,the development of supramolecular chemistry is inseparable from the discovery and development of supermolecular hosts(or receptors),and from the discovery of crown ethers to the development of cyclodextrins,calixarenes,cucurbiturils and pillararene,it has been experienced a long process.Cucurbit[n]urils(CB[n]s,n = 5–8,10,13–15)are a kind of macrocyclic hosts developing rapidly in recent years and have played important roles in supramolecular hostguest chemistry.On one hand,the negatively-charged carbonyl rims provide binding sites for non-covalent interactions including ion-dipole interaction and hydrogen bonding interaction.On the other hand,the inner hydrophobic cavity surrounded by glycoluril units are favorable for holding hydrophobic groups/neutral molecules.CB[n]s are endowed with high selectivity and affinity towards guests,which plays important role in molecular recognition,supramolecular catalysis,supramolecular polymers/materials,drug delivery and biomedical systems,and other potential applications in supramolecular chemistry.With the biggest cavity in the CB[n]s family,CB[10] shows its unique molecular recognition properties that are rather distinctive from other CB[n]s.So far,there are only ~ 23 research articles involving CB[10],which is much less than those involving CB[7] and CB[8] discovered at the same period as CB[10],the main problems are the low yield of CB[5]@CB[10] and the difficult isolation of CB[10].In this dissertation,we summarized the progresses in CB[10]-based chemistry since CB[10] was first reported as CB[5]@CB[10] complex in 2001.Purification,molecular recognition and cooperative effects of CB[10] will be described and an outlook will be given for further exploration of CB[10]-based chemistry.1.Purification of CB[10].We found that the addition of a specific guest into a relevant mixture of CB[n]s in 6M HCl allowed the displacement of CB[5] from CB[5]@CB[10] to form precipitate.Subsequent washing of the resulting precipitate-Gn@CB[10](G = guest)with DMSO,enabled to get pure CB[10] in a facile and highly efficient way.The formation of three types of binding modes were observed depending on the inclusion host–guest ratio,1:1,1:2 and 1:3 that were mainly dictated in this series by the size of the guests.2.The molecular recognition of CB[10] with macrocyclic hosts and its cooperative recognition research towards guests:a.CB[10] had been found to form stable host-guest complexes with cyclophanes,those complexes were soluble in both water or DMSO.The recognition properties of cyclophanes were deeply affected by the presence of CB[10] with both positive and negative cooperative effect towards guests.In most cases,encapsulated by CB[10],cyclophanes showed their weak binding towards anions,due to the conformation of cyclophanes in the complexes were unswitchable for binding anions.Neutral compounds such as phenol formed ternary inclusion complexes with cyclophanes@CB[10] by hydrophobic effect.b.The host-guest interactions between CB[8]/CB[10] and calix[4]pyridinium and its derivative were also investigated,which were found to form a 1:1 supramolecular inclusion complexes by electrospray mass spectrometry.The molecular recognition properties of calix[4]pyridinium and its derivative with a series of neutral guest molecules and anion compounds were also investigated by fluorescence titrations.3.The host-guest interactions between CB[7]/CB[8] and Auramine O(Au O)dye were investigated in aqueous solution.The results indicated the simultaneous formation of 1:1 and 2:1 inclusion complexes between CB[7] and Au O in phosphate buffer,and 1:2 homoternary inclusion complex Au O2@CB[8].Interestingly,appearance of intense new broad emission band with big red-shift(100 nm)with respect to that of Au O proves the formation of excimer upon encapsulation of Au O molecules in CB[8].Determination of single crystal structure of Au O2@CB[8] further disclosed the existence of J-type dimer with intermolecular CH···? interactions between two included phenyl groups on Au O molecules.With the study of this dissertation,a new method for the preparation of CB[10] was proposed,and the property of its host-guest recognition was further explored,which provided a new opportunity for the development of the CB[10].