Self-assembly, Molecular Recognition Of Macrocyclic Amphiphiles And Their Functionalization

In recent years,more and more macrocyclic and supramolecular chemists have focused their research attention on amphiphilic self-assembly,leading to the birth of a new class of amphiphilic molecules-"macrocyclic amphiphiles".Macrocyclic amphiphiles are obtained by suitably modifying macrocyclic molecules(cyclodextrins,calixarenes,pillararenes,etc.).Compared with traditional linear amphiphilic molecules,macrocyclic amphiphiles integrate multiple hydrophilic head groups and hydrophobic side chains on their pre-organized scaffolds,exhibiting several pronounced selfassembling features,such as high aggregation stability,low critical aggregation concentration and uniform size/shape.More importantly,the most superiority of macrocyclic amphiphiles that cannot be obtained by traditional amphipathic molecules is their recognition sites on the self-assembling surface,which makes macrocyclic amphiphiles known as “surfactants with specific host-guest recognition sites”.Based on the host-guest recognition of macrocycles on the self-assembling surface,the morphology of the assembly can be tuned,non-covalent modification of specific functional groups can be achieved,and hierarchical self-assembly can be further performed.In this thesis,a series of supramolecular systems based on amphiphilic cyclodextrin and calixarene were constructed to explore new functional aggregates.The potential applications in the fields of luminescent materials and biomedicine were investigated.The major contents of this thesis are as follows: 1.An artificial light-harvesting platform was constructed from amphiphilic calixarenes via self-assembly and host-guest complexation strategies.In this platform,energy donors and acceptors in the light-harvesting system are encapsulated in the calixarene cavity and entrapped in the hydrophobic layer of the assembly,respectively.The compartmentalization effect of the calixarene cavity can effectively suppress the selfquenching of the fluorescent molecules.At the same time,benefiting from the spherical structure of the vesicles,the energy donors included on the surface of the vesicles can effectively absorb the light energy and shuttle energy from donor to donor and ultimately to the acceptor.Varying the molar ratios between donor and acceptor allows for the fine-tuning of the energy transfer process and broad-spectrum outputs,suggesting promised application as fluorescent inks with capability of encryption coding.2.A new type of tunable photoluminescent material was developed using a co-assembly of amphiphilic cyclodextrin and amphiphilic calixarene.In this system,three different chromophores were individually encapsulated in the cyclodextrin cavity,in the calixarene cavity,and entrapped in the hydrophobic bilayer of the assembly,respectively.As a result,an efficient cascade energy transfer among three chromophores was generated.A large matrix of colors was realized by delicately tuning the molar ratios of chromophores,which occupies most of the area in the Commission Internationale de l'Eclairage(CIE)chromaticity diagram.When the system is transferred from the solution state to the solid state,it can still maintain the tunability of cascade energy transfer and emission spectra.Thus the elaborated supramolecular ‘‘cocktail'' hides a dual-encryption coding,exhibiting feasible application as fluorescent security inks that are difficult to counterfeit but easy to authenticate.3.A new artificial heteromultivalent platform was developed by the co-assembly of amphiphilic cyclodextrin and amphiphilic calixarene.The heteromultivalent system shows strong and selective binding towards tyrosine-/lysine-rich peptides,validated by the measurement of binding constants towards a series of model peptides.As a proofof-concept application,we successfully engaged the cyclodextrin/calixarene coassembly in inhibiting the A? fibrillation as well as dissolving A? fibrils.