Dynamic Covalent Chemistry And Supramolecular Self-assembly Of Fluorescent Molecules

In contrast to traditional covalent chemistry,supramolecular chemistry is based on noncovalent interactions such asπ-πstacking interaction,hydrophobic interaction,hydrogen bonding,metal ion coordination,electrostatic interaction and host-guest interaction.So far,it has been applied in drug delivery,solar cell,electronics,stimuli-responsive materials,targeted therapy and so on.In this thesis,three strategies are used to construct the functional molecules,including amphiphiles,disc-like dendrimers and hydrogen-bonding unit conjugation.In particular,the new synthesized amphiphiles contain dynamic covalent bonds,thus demonstrate the dynamic properties.The research content is summarized as follows:（1）Amphiphilic N-phenylcarbazole maleimide-furan adducts were synthesized and fully characterized using the Diels-Alder reaction.Single crystal X-ray diffraction revealed that the length of dynamic covalent bonds is 1.56?,which is longer and weaker than normal covalent bonds.¹H NMR spectroscopy revealed that the furan moieties of these new maleimide-furan amphiphiles can be exchanged in mixing systems due to dynamic Diels-Alder reactions,thus,two new maleimide-furan compounds can be transformed each other.Thus,the maleimide-furan amphiphiles displayed the reversible fluorescence OFF/ON behaviours and the interesting H-bonding driven supramolecular assembly.（2）Amphiphilic adducts and model compound were synthesized and fully characterized using the Diels-Alder reaction between trismaleimide and hydrophilic furan derivatives.Two kinds of furan derivatives with dansylamide unit were synthesized and fully characterized.Nanotublar aggregates were observed from the TEM measurements.As revealed by X-ray crystal structure studies,model compound molecules are propeller-like geometry structures with intermolecular hydrogen bonding being formed.Furthermore,chiral self-sorting happens in model compound.In concentration-dependent ¹H NMR experiments,the results of TOCSY and ROSEY confirmed the formation of hydrogen bonds in solution.The amphiphiles can be destroyed and reformed reversibly with reversible fluorescence OFF/ON behaviours.Thus,two new maleimide-furan compounds can be transformed each other.¹H NMR spectroscopy revealed that the furan moieties of these amphiphiles can be exchanged with furan derivatives congugating dansylamide unit.（3）By using Michael addition,one new class of dendrimers with 12 long alkyl chains surrounding a dendrimer hard core,where trismaleimide served as building blocks,piperazine diamine as connecting unit,was synthesized and and fully characterized.AFM image revealed helicaities formed in methylcyclohexane.Single crystal X-ray diffraction study revealed that the building block molecules are C₃-symmetrical with propeller-like geometry structures.The results of concentration-dependent ¹H NMR,TOCSY and ROSEY confirmed that helical supramolecular polymer forms through the hard core of disc like dendrimer packing together by solvophobic interaction.（4）Two boron-dipyrromethene dyes bearing a conjugated guanine unit were synthesized and fully characterized.As revealed by X-ray crystal structure studies,G-BODIPY dye self-assembled into ribbon-like structure due to the intermolecular hydrogen bonding andπ-πstacking interaction.In concentration-dependent ¹H NMR experiments confirmed the formation of hydrogen bonds of the guanine units in solution of G-BODIPY dyes.In the presence of K⁺,the characteristic signals for the formation of cyclic G-quadruplex structure were observed in ¹H NMR study.The aggregation of G-BODIPY dyes was further monitored by UV/Vis absorption spectroscopy by varying the solvent polarity and temperature.H-type aggregates of G-BODIPY which was characterized by a new hypsochromically shifted absorption band was obtained.In the presence of K⁺,the enhancement of stability was observed for the H-aggregates.