Rational Design,Assembly And Properties Of Functional Metal-Organic Cages

Metal-organic cages?MOCs?have been widely investigated for their bionic feature and potential applications?e.g.stabilization of reactive species,recognition,and catalysis?.This is even challenging for chiral cages,which are of particular interest because of the increasing demand for materials for chiral recognition,asymmetric catalysis and enantioseparation.In this thesis,we have synthesized three series of cages:chiral triple-stranded helicate cages,chiral tetrahedral cages and cubic cages.¹H and ¹³C NMR,¹H-¹H COSY,NOESY,DOSY NMR,Quadrupole time-of-flight mass spectrometry?Q-TOF-MS?suggested the formation of a discrete and highly symmetric assembly and their stability in solution.The structures and properties of these MOCs were characterized by a variety of techniques such as single crystal X-ray diffraction,UV-vis spectra,fluorescence spectra.Their applications in chiral fluorescent recognition,asymmetric catalysis and cavity-confined acceleration of chemical transformations in the cavity of MOCs were explored.This thesis includes the following five chapters.In Chapter 1,firstly,supermolecular chemistry and research background of metal-organic cages were introduced,including design principles to achieve specific cages molecular recognition and storage,sensing,catalysis,drug transporters,synthetic ion channels and so on.The opportunities and challenges remained in chiral MOCs area together with overviews of the topic and research progress were also discussed and presented.In Chapter 2,four diamine ligands based on Biphenol were designed and synthesized,and four chiral helicates?H-1,H-2,H-3 and H-4?were constructed by coordinated with Zn^II ions.The intensity of fluorescence of the H-1 and H-3 was greatly enhanced by series of enantiomeric amino alcohols in solution with enantioselectivity factor up to 9.35.In Chapter 3,five chiral single-and mixed-linker tetrahedral coordination cages were designed and constructed using six dicarboxylate ligands derived-from enantiopure Mn?salen?,Cr?salen?and/or Fe?salen?as linear linkers and four Cp₃Zr₃clusters as three-connected vertices.The cages feature a nanoscale hydrophobic cavity decorated with the same or different catalytically active sites and the mixed-linker cage bearing Mn?salen?and Cr?salen?species is shown to be an efficient and recyclable catalyst for sequential asymmetric alkene epoxidation/epoxide ring-opening reactions with up to 99.9%ee.The cage catalyst demonstrates improved activity and enantioselectivity over the free catalysts owing to stabilization of catalytically active metallosalen units and concentration of reactants within the cavity.In Chapter 4,here we report the design and self-assembly of two cubic coordination cages with a general formula[Zn₈L₆?OTf?₁₆]were designed and constructed using six C₂-symmetric tetrakis-bidentate ligands derived from tetraphenylethylene as faces and eight C₃-symmetric zinc?II?tris?pyridylimine?centers as three connected vertices.In particular,the hydrophobic cavities of the cages are able to accommodate two different kinds of aromatic molecules such as anthranilamide and aromatic aldehydes through supramolecular interactions,thereby allowing for a sequential condensation/amine addition of the guests to produce non-planar 2,3-dihyroquinazolinones.The reaction is highly efficient with high rate enhancements(up to 38000 of the k_cat/k_uncatncat ratio)and multiple turnovers in comparison to the bulk reaction mixture.In Chapter 5,a briefly summary and prospect of this thesis were given.