Study On Supramolecular Assemblies And Applications Of Cucurbit[8]Urils With Cationic Dyes

Cucurbit[n]urils(CB[n], n=5-8,10), as the fourth generation supramolecular host after crown ether, cyclodextrin and calixarene, have attracted great attention in the field of supramolecular chemistry for their unique structure properties and broad application prospects. The domestic and international research groups have taken extensive and deep studies on cucurbit[n]urils and made great progress in the field of molecular recognition, catalysis, material science, biomedicine and so on.In the aim of further revealing the mechanisms of molecular recognition and assembly based on cucurbit[8]uril with viologen derivatives and exploring application of CB[8] in the field of biological science, a series of cation dyes based on viologen and its derivatives was designed and synthesized. The self-assembly behavior and recognition of these guest molecules and their radicals was studied. Furthermore, the structure of guest dyes in the influence of the self-assembly behavior and recognition mechanisms was discussed systematically. Finally, a near infrared dye was synthesized and formed inclusion complex with CB[8]. This inclusion complex exhibited ultrastable photostability with well mitochondria staining capability, this work explored the application of CB[8] in the field of biological imaging.The major contents of this thesis are as follows:1. The recent progress and important achievements on supramolecular self-assembly of cucurbit[n]urils were reviewed.2. A series of viologen derivatives with different chain length were synthesized, and their self-assembly mode and binding capability were characterized by using NMR, MS, UV-Vis spectrum and electric potential. The results showed that three guest dyes were assembled with CB[8] by the ratio of1:1, while their binding mode and self-assembly behaviors varied greatly. The driving force of PMV binding CB[8] was hydrophobic effect. As the result, the benzene ligand was included in the cavity of CB[8] while the viologen part was left outside. For PEV and PPV, the assembly driving force was spatial effect and ion-dipole effect, so these two guest were folded in the cavity of CB[8], forming a charge-transfer (CT) complex. In the study of the radical product of these three guest dyes with CB[8], PMV+· formed2:1radical dimer complex with CB[8], while for PEV+· there existed a dynamic balance in two forms,2:1complex and1:1complex. The guest PPV+· only formed a stable1:1inclusion complex with CB[8].3. A series of viologen derivatives with different O-atom contained ligand were synthesized, and their self-assembly mode and binding capability were characterized in the method of NMR, MS, UV-Vis spectrum and electric potential. The self-assembly behavior of their reduced radical products with CB[8] were also investigated. The results showed that these three guest dyes form1:1CT complex with CB[8] through spatial effect and ion-dipole effect as the driving force. However, the O-atom of the ligand and the ratio distribution with CB[8] in solution influenced the self-assembly dynamic balance of their radical product with CB[8]. In the case of equal ratio for the guest dye and CB[8], three dyes radical product formed2:1and1:1coexisting complex with CB[8]. As comparison, PPV+· only formed1:1inclusion complex with different ratio of CB[8]. The molecule simulation calculation were used to study the relative binding energies of radical monomer complexes and radical dimer complexes of these four complex. The results revealed that only the relative binding energy of PPV+·@CB[8] was higher than (PPV+·)2@CB[8] while the binding energy of the other three guest radical were lower than their radical dimer in the inclusion with CB[8]. This phenomenon could attribute to the O-atom in the ligand. For the bond angle of C-C-C is smaller than C-O-C, the guest molecule PPV could folded in the cavity of CB[8] more easily. In another hand, without the repulsion force between O-atom and CB[8]’s carbonyl group at the portals, PPV+·CB[8] could be much more stable than its radical dimer complex.4. A near infrared dye PQ with large Stokes shift was synthesized. This dye perform well mitochondrial staining capability. CB[8] host forms stable complex with PQ and prevents PQ aggregation in aqueous solution, resulting in a dramatic increase in fluorescence intensity, and the photostability of this complex was greatly improved comparing with that of PQ dye alone. The celluar staining experiment revealed that PQ@CB[8] complex has good cell penetrating ability, low cytotoxicity, and well located at mitochondria with high re-stain rate. This work explored the application of CB[8] in the field of biological imaging.