Construction And Properties Study Of Complex Mechanically Interlocked Structures Based On Metallacycles

Mechanically interlocked molecules(such as catenanes,rotaxanes and molecular knots)have attracted extensive attention by chemists for their delicately topologic architectures and wide applications in molecular machines(molecular switches,molecular motors,molecular sensors,molecular catalysis and molecular synthesizers)and smart materials(storage devices and molecules muscle).The integration of a simple mechanically interlocked structure into higher-ordered structures containing multiple mechanically interlocked components would definitely improve the mechanical properties and endow themselves multifunction owing to their synergistic effect of functional sites.The strategy to construct such complexity is of great challenge and interest,and the main well-established methods to date include covalent bond and non-covalent bond approach.However,covalent bond approach always results in a mixture of various mechanical interlocking complexes accompanying with tedious separation and relatively low yield since the covalent bond is kinetically controlled during the construction process.In contrast,non-covalent bond approach is the most versatile and has successfully demonstrated to efficiently construct various mechanical interlocking structures because the non-covalent bond formation is reversible and thermodynamically controlled.In the last decades,a lot of efforts have been devoted to highly efficient synthesis of supramolecules via non-covalent interaction,resulting in different kinds of mechanically interlocked systems.On this basis,the objective of this dissertation is to further expand the system of higher-ordered structures containing multiple mechanical interlocking components with non-covalent bonds.To achieve this aim,a series of new mechanically interlocked complexities were successfully constructed by modifying organometallic coordination macrocycle and using a variety of non-covalent bond synergies,and their corresponding special properties were systematically studied.There are five parts in this dissertation:Chapter one,the development of mechanically interlocked structures is systematically reviewed,including the research progress of some classical mechanically interlocked structures,and their construction strategies and methods.The research progress of constructing mechanically interlocked structures based on non-covalent bonds is particularly highlighted.From the literature review it is found that higher-ordered structures containing multiple mechanically interlocked components have been seldom studied due to their challenging synthesis,let alone their properties and applications.This motivates and directs the research focus of this thesis,and works are presented in the following four chapters.Chapter two,the content of this chapter is mainly to construct two kinds of polypseudorotaxane structures with redox reversible stimuli response by multi-stage assembly.In the primary assembly,Cu(I)-phenanthroline complex was used as a template and redox stimulation site,and a linear molecule containing a cyano chain at the end was used as an axle to construct a[2]pseudorotaxane with a 120~o pyridine donor.Two metallocycles with multiple[2]pseudorotaxane were constructed with 60~o and120~o double platinum receptors via coordination-driven self-assembly in secondary assembly.In the tertiary assembly,two poly[3]pseudorotaxanes based on organometallic frameworks were successfully constructed by the host-guest interactions between the pill[5]arene dimer and the terminal cyanoalkyl chain.The redox reversible stimuli responsiveness of the two poly[3]pseudorotaxane structures were thoroughly investigated by nuclear magnetic resonance(NMR),ultraviolet absorption spectroscopy(UV),scanning electron microscopy(SEM),and diffusion-sequence nuclear magnetic resonance(DOSY).Because of the different structural symmetry of Cu(I)-phenanthroline complexes in different oxidation states,the diffusion coefficient of two poly[3]pseudorotaxane were controlled by redox.Chapter three,in the work of this chapter,a discrete octadeca-[2]pseudorotaxane structure is constructed by hierarchical self-assembly strategy.The[2]pseudorotaxane in the second chapter was used as the building block,and the hexa-[2]pseudorotaxane was efficiently constructed with 180°accepter by coordination driven self-assembly.The neutral guest cyano group at the end of the linear molecular axis of the[2]pseudorotaxane with the host containing the pill[5]arene are further assembled into the octadeca-[2]pseudorotaxane structure through host-guest interaction.Chapter four,five heterometallic molecular necklaces were efficiently constructed by coordination driven self-assembly for the first time.The phenanthroline derivative containing pyridine or carboxylate complex site was used as the molecular axis,and 60°or 180°[2]pseudorotaxanes were constructed with the three kinds of angles molecular axis based on carboxylate and pyridinyl by the Cu(?)template.Because the linear molecular axis in[2]pseudorotaxane has a specific directional and structural rigidity,[2]pseudorotaxane as a versatile building block together with complementary acceptors would ideally generate five heterometallic molecular necklaces(two[3]catenanes,two[4]catenanes and[7]catenane),by means of coordination-oriented self-assembly.The application of such molecular necklaces in DNA cleavage was also examined in this work,i.e.,four heterometallic molecular necklaces with 60°pyridine ligand or 60°carboxylic acid ligand have a strong cutting effect on pBR 322 DNA.It was found by gel electrophoresis that the molecular necklace had better cutting efficiency than the corresponding[2]pseudorotaxane and double platinum receptor at the same concentration and same incubation time.This is mainly due to the synergistic effect of heterometals,which makes the cutting effect more efficient.Therefore,both[3]molecular necklaces and[4]molecular necklaces can be used as a novel artificial nuclease for DNA cleavage.Chapter five,we have controllably constructed a hybrid polypseudorotaxane structure by hierarchical self-assembly strategy.Firstly,the amine-based control site modified metallacycle was constructed by coordination driven self-assembly,and the peripheral amine were protonated ammonium cation in the metallacycle with crown ether modified with a long alkyl chain for constructing tris-[2]pseudorotaxane metallacycle structure.Furthermore,the heparin sodium was used as the linear molecular axis with metallacycle for constructing the inorganic-organic polypseudorotaxane through electrostatic interaction,and the crown ether was complexed at the periphery of polypseudorotaxane by the host-guest interaction.Therefore,we successfully constructed multi-component and hybridization polypseudorotaxane assembly.It was found that a high concentration of tris-[2]pseudorotaxane and a low concentration of the tris[2]-polyrotaxane-heparin sodium system as gelling factors can form two organometallic gels in acetone.Based on the dynamic reversibility of the platinum-nitrogen bond and the host-guest interaction between the crown ether and the amine-based control site,the metal-organic gel is given multiple stimuli response properties.