Supramolecular Self-assembly Based On Imine Condensation

In the field of supramolecular chemistry and self-assembly,imine condensation could be employed to synthesize molecules with complex structures in high yields,because of the reversible nature of imine that allows the systems to search for their most thermodynamically favored states.We focus on discussing the work of using Schiff s base and its derivatives in the field of self-assembly.Therefore,in the first chapter of this thesis,we summarize the research on self-assembly based on noncovalent interactions and dynamic bonds.We also discuss the reason why dynamic approaches can afford high yields in self-assembly.In the second chapter,we employed imine condensation,in the synthesis of two different three-dimensional molecules,including a triangular pill-shaped molecule and a tetrahedron.The ratio of these two self-assembled products could be switched by tuning temperature and concentration,which changed the thermodynamic stability of these two products.These two molecules were fully characterized by using a number of techniques,including ¹H NMR,¹³C NMR,DOSY,COSY,NOESY,ESI-HR-MS,MALDI-TOF-MS,X-ray diffraction analysis.In organic solvent,these two molecules are highly luminescent,due to their fluorene building blocks.It is noteworthy that,the pill contains two tris-imino residues that contain more convergent coordinative nitrogen binding sites compared to the tetrahedron.Addition of metals including Ag⁺,Zn²⁺,Cu⁺,Fe²⁺,Ni²⁺,Co²⁺,to the mixture of pill and tetrahedron shifted the equilibrium to the pill side.Upon addition of silver cation,the fluorescence of the self-assembled molecules undergoes quenching,while other cations lead to little or weaker luminescence change.The implication is that,the pill molecule could be used as a chemical sensor for detecting silver cation.In the third chapter,we thus discussed the possibility of using this self-assembled pill/tetrahedron system to de'velop a silver?I?cation sensor.Even although imine condensation is used in organic solvent for self-assembly,the imine bond contains a relatively electrophilic carbon atom,which is apt to undergo hydrolysis in the presence of water.As a consequence,imine condensation is considered not feasible to use in water.In order to solve this problem,in chapter four,we used an ?-substituted imine,namely acylhydrazone,which is less electrophilic compared to parent imine,to perform self-assembly in water.We realized the self-assembly of a triangular prism in water,whose guest recognition ability was investigated.