Study On The Construction And Properties Of Chiral Anion-Based Coordination A₄L₄ Cages

Supramolecular assemblies have attracted much attention due to their structural diversity and functional richness.The construction and properties of metal-based coordination supramolecular cages have been extensively studied,while anion-based coordination cages have been gradually recognized.In this thesis,a series of C₃ tris?bisurea?ligands Lⁿ with different terminal groups were designed,which formed A₄L₄ type cage?“A”for anion and“L”for ligand?with phosphate(PO₄^3-).The effects of different terminal groups on the construction of anion supramolecular cages were discussed,and the construction and properties of chiral anion cages were further studied.This is of great significance to the structure design and properties of anion supramolecular cages.This thesis is mainly divided into three chapters,which respectively introduce the following contents.The first chapter is an introduction.The origin and research progress of self-assembly supramolecular system and its'chirality,the construction,development and application of tetrahedral supramolecular cages based on metal coordination be summarized.The research progress of chiral supramolecular assemblies based on metal coordination,the design of urea-receptors and self-assembly also be summarized,which inspires the topic selection and research significance of this thesis.In Chapter 2,previous research shows that a C₃ symmetric tris?bisurea?ligand L¹ can form A₄L₄ type cage with phosphate(PO₄^3-).Herein further changed its terminal group and explored the properties of the new ligands,L²-L⁴.It proved that the change of terminal group does not affect the construction of tetrahedral cage by the means of crystal,NMR and MS.While it affects the optical properties of the assembly by the means of UV-vis and fluorescence.The fluorescence provided a convenient detection method for further application.Furthermore,the post-assembly modification of tetrahedral cage by introducing reactive terminal functional groups is still going on.In Chapter 3,the construction of chiral anion supramolecular cage was studied.In the crystal structure of the ligand L⁴ with phosphate,a pair of tetrahedral cages?????and?????was found in the same unit cell.In order to obtain enantiopure homochiral tetrahedral cage,two sets of ligands(L^R/S,L^2R/2S)with different distances between the chiral point and urea group were designed.By the means of crystal,NMR and MS,the conclusion that they still formed A₄L₄ cages was drawn.The ligand L^R/S which chiral site is directly linked to the urea group assembled into a homochiral tetrahedral cage.While the other ligand L^2R/2S which shifts the chiral center to one carbon away from the urea site may assembly racemate or in a mixed state by further CD measurements.Chiral amplification was found when chiral ligand and non-chiral ligand L² were mixed and assembled.Chiral amplification also exists in anionic coordination chemistry and enlarges the examples of C₃ ligand.