| The supramolecular metal-organic cages are the supramolecular complexes which are constructed by metal ions and structure-matched ligands via coordination-driven self-assembly.They have widely potential application in molecular recognition and encapsulation,molecular delivery,ion detection,catalysis,and other fields.As the rapid development of supramolecular chemistry,the methods of coordination-driven self-assembly have also matured,leading to newer and more topologically versatile architectures.In addition to the curiosity to establish new topological structures,applications of functionalized supramolecular cavities have been extensively investigated.Nowadays,chemists have aroused an exciting interest and high attention in biomimetic catalysis based on supramolecular metal-organic cages.In this thesis,the designed Pd4L 2,Pd4L 2 homoleptic cages and Pd5L21L02 heteroleptic cage have remarkable capability to encapsulate a series of substrates.The self-assembled coordination Pd4 L12 cage is employed as a water-soluble molecular flask for the synthesis of functionalized coumarins from a range of salicyladehyde derivatives and cyanoacetates/malononitrile.The main conclusions are as follows:1.Design and synthesis of a series of assembled functionalized ligands which possess pyridinium cationic moieties and are synthesized from two 2,4,6-tris(4-pyridyl)-1,3,5-triazine(TPT)with a p-xylene or 4,4’-dimethylbiphenyl linker.Then,homoleptic Pd4L12,Pd4L22 and heteroleptic Pd5L21L02 supramolecular metal-organic cages are constructed successfully by two pyridinium-functionalized bis-bidentate ligands,TPT and four cis-blocked palladium corners(en-/tmen-Pd(NO3)2)through coordination-driven self-assembly in water.Those cages are clearly characterized by NMR spectra and single-crystal X-ray diffractions.Those supramolecular metal organic cages possess an enlarged-size hydrophobic cavity and keep benign water solubility.2.A series of ring molecules are identified and encapsulated into the Pd4L12 Pd4L22 and Pd5L21L02 cages.The formation of host-guest complexes is evidenced by NMR spectra,three of which are characterized by single-crystal X-ray diffractions.Different steric cavities of those supramolecular metal-organic cages influence on the binding affinity and the amount of guests encapsulated.Different shapes and sizes of substrates also have an impact on the interaction ability.Suitable crystals are obtained by slow evaporation of the aqueous solution of the host-guest complexes.The crystal structures show the space distribution and spatial configuration of guest molecules unambiguously.Molecules are sitting inside Pd4L12 cage by stabilization of π-πstacking interactions between guest molecules and the TPT panels of the cage.In the level of functionalized supramolecular cage,host-guest interaction is the premise and foundation for various applications in molecular recognition,molecular delivery,catalysis,ion detection and other fields.3.A self-assembled coordination Pd4L12 cage is employed as a water-soluble molecular flask for the synthesis of functionalized coumarins from a series of salicylaldehyde derivatives and cyanoacetates/malononitrile.The catalytic reaction features mild aqueous conditions and broad substrate scopes.Taking 2-hydroxy-1-naphthaldehyde with ethyl cyanoacetate reaction for example,we carried out background reaction,control experiment and inhibition reaction in the common conditions.The yield of product is more satisfactory under Pd4L12 cage than the others.In this typical case,Michaelis-Menten kinetic studies were performed,revealed that the rate of product formation had been enhanced by over 23-fold in contrast to the background reaction without cage.In order to clarify the rate determining step,one analogous intermediate had been obtained with 1-naphthaldehyde and methyl cyanoacetate.The first reaction step,Knoevenagel condensation-elimination reaction is rate determining step.Finally,we shed light on a reasonable supramolecular reaction mechanism. |
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