Construction Of Functional Supramolecular Systems Based On Pillar[n]arenes And BODIPY And Their Applications

Pillar[n]arenes are a new class of host molecules,which are cyclic oligomers consisting of hydroquinones or 1,4-disubstituted hydroquinone ethers linked by methylene bridges in the para positions of the benzene rings.Since they were first found in 2008,the symmetric plliar-shape structure,electron-rich cavities and facile functionalization endow pillar[n]arenes unique and excellent host-guest propeties to construct various supramolecular assemblies such as(pseudo)rotaxanes,catenanes and supramolecular polymers.Recently,researchers pay more attention to the potential functions and applications of pillar[n]arenes.As a result,they begin to devote themselves to the construction of functional supramolecular systems including amino acid recognition,fluorescence sensors,artificial transmembrane channel,and drug delivery systems and so on,which are involved in material science,medicinal chemistry,biochemistry,and life sciences.These researches greatly promote the development of pillar[n]arene chemistry.This thesis is focused on the pillar[n]arene hosts and further introducing functional BODIPY groups into the host or guest molecules to construct supramolecular assemblies.Furthermore,functional supramolecular systems including artificial light-harvesting systems and drug delivery systems are constructed via host-guest interactions.The detailed research contents exhibit as follows:In the first part,we have designed and prepared a BODIPY-bridged pillar[5]arene dimer P5-BDP-P5 and four porphyrin derivative guests G1-G4 to construct FRET supramolecular assemblies for mimicking photosynthetic light-harvesting system.1HNMR spectra show that only G1 and G3 can be recognized by P5-BDP-P5.The FRET propeties of GlcP5-BDP-P5 and G3(?)P5-BDP-P5 assemblies are investigated by UV-Vis absorption and fluorescence emission spectra.The results imply that FRET exists in both assemblies but the effects are very poor.Further modifications on the chemical structures of host and guest molecules are needed to enhance the FRET effect.In the second part,we have designed and prepared a BODIPY-bridged pillar[5]arene dimer P5-BDP-P5 and two BODIPY derivative guests G5/G6 to construct AA/BB-type and A2/B3-type FRET supramolecular polymers for mimicking photosynthetic light-harvesting system.Both assemblies exhibit very strong absorption in a broad region from 300 to 700 nm.They show efficient FRET effects and the transfer efficiency is 51%or 63%,which is comparable with previous artificial models.To the best of our knowledge,this is the first example of pillar[5]arene-based supramolecuar assemblies for mimicking the light-harvesting system.Therefore,this work not only provides a novel model for fabricating artificial light-harvesting systems but also extends the potential applications of pillar[n]arenes in the field of optoelectronic materials.In the third part,we have constructed novel supramolecular vesicles based on the host-guest interaction between water-soluble pillar[5]arene(WP5)and a BODIPY-functionalized derivative G7,in which G7 plays a dual role,acting not only as a guest molecule but also as a photosensitizer for photodynamic therapy.Chemotherapic drug DOX is successfully encapsulated into these vesicles and the resulting DOX-loaded vesicles are stable under physiological conditions but exhibit effective and rapid release of DOX in low-pH environment.Furthermore,the in vitro cytotoxicity and cellular internalization experiments suggest that these DOX-loaded supramolecular vesicles,entering cancer cells mainly via endocytosis,can well localize in lysosomes and show remarkable combination of chemo-and photodynamic activities against A549 cancer cells,thus this novel kind of drug nanocarrier is expected to be a suitable and potential supramolecular drug delivery system for chemo-photodynamic dual therapy.To the best of our knowledge,this is the example of pillar[n]arene-based supramolecular drug nanocarrier for effective combined cancer treatment.In the fourth part,after many failures in synthesizing the symmetric or asymmetric BODIPY-based diselenides,we have successfully designed and prepared a bola-form diselenide guest G8,but this work is suspended because of time and other reasons.In the future,we hope to construct dual redox responsive supramolecular assemblies based on the host-guest interactions of WP5 and G8 for drug delivery.In summary,functional supramolecular systems including artificial light-harvesting systems and drug delivery systems are constructed on the basis of molecular recognition and assembly of pillar[n]arenes in this thesis.Researches from structure synthesis to functions and applications are attempted,which is also in accord with the development tendency of pillar[n]arenes.We hope this thesis will provide some benefits and reference value for functional supramolecular systems based on pillar[n]arenes.