Construction Of Stimuli-responsive Supramolecular Assembly Systems

Self-assembly refers to the process in which assembly motifs spontaneously form an ordered structure through weak interaction forces between molecules,and is considered as an important means for creating new substances and materials.The stimuli-responsive supramolecular assembly system is a type of macromolecular system with"smart"behavior.It can receive stimulation signals from the external environment,such as pH,light,temperature,voltage,redox agent,gas and so on,which will induce large changes in the structure or state of these macromolecules,thus affecting its physical and chemical properties,and thus reflecting the corresponding functions.A large number of studies have shown that the stimuli-responsive supramolecular system has a wide range of applications in the fields of nanomaterials science,life sciences,and clinical medicine.Based on different strategies such as coordination bond and hydrogen bond self-assembly,we have constructed supramolecular assembly systems with photoresponse,solvent response,and small molecule reagent response.Firstly,the chiral tunable supramolecular metallacycles were successfully constructed via coordination-driven self-assembly.Secondly,a luminescent metallacage was constructed through the same assembly strategy,and its hierarchical self-assembly behavior was studied.Finally,from the development of functionalization system to the study of assembly mechanism,a hydrogen-bonding self-assembly strategy was used to design and synthesize the system of cassemblysis,and the kinetic properties of the system of cassemblysis were studied.Chapter one,the concept of self-assembly and its development status were briefly introduced.The research progress of self-assembly systems and stimuli-responsive supramolecular assembly systems were reviewed.Then our projects in this paper were put forward.Chapter two,bisthienylethene nitrate receptors and a chiral binaphthol pyridine donor were designed and synthesized.Then a series of bisthienylethene-based chiral supramolecular metallacycles were constructed via coordination-driven self-assembly.Due to the introduction of bisthienylethene,the resulting supramolecular metallacycles were photoresponsivity.Under irradiation of light at a specific wavelength,the reversible interconversion between an opened-form structure and a closed-form structure of these supramolecular metallacycles could be realized.In addition,the chirality of these metallacycles can be regulated by light stimulation.Chapter three,A new type of supramolecular metallacage with fluorescence properties was constructed by combination of coordination-driven self-assembly with Pt···Pt and?-?stacking interactions.Its structure was characterized by ¹H NMR,¹⁹F NMR,DOSY,ESI-TOF-MS,and molecular simulation.The metallacage is solvent-responsiveness and can emit different wavelengths of fluorescence in different solvent systems.Moreover,it can spontaneously form stable metal organogels at room temperature through hierarchical self-assembly.Chapter four,a system of cassemblysis with chiral memory behavior was constructed through hydrogen bond-driven self-assembly and ligand regulation.The addition of small molecule cassemblyst can speed up the racemization process of these systems.The kinetic properties of the racemic processes of these assemblies were studied by establishing kinetic models and combining circular dichroism.It was found that the addition of a cassemblyst could reduce the activation energy of the racemization process of the systems of cassemblysis.Based on these results,the possible mechanism of the racemization process was proposed.