Design And Properties Of Pillar[5]arene Based (Pseudo) Rotaxanes And [1]rotaxanes

Supramolecular chemistry,which is a multidisciplinary involving chemistry,biology,physics,materials,information science and environmental science,has profound academic backgrounds and potential research values.Supramolecular chemistry emerged with the vigorous development of macrocyclic compounds,especially with the emergence of crown ester,calixarene,cyclodextrin,cucurbituril and pillararene.Pillararene,discovered by Tomoki Ogoshi in 2008 and underwent ten years of in-depth exploration,whose structural modifications and potential applications made a fast promotion and development.Pillararene is a cylindrical compound formed by cross-linking of 1,4-dimethoxybenzene or its derivatives via methylene bridges.According to the number of 1,4-dimethoxybenzene and its derivatives,pillararene can be divided into pillar[n]arene from pillar[5]arene to pillar[10]arene.Because of symmetrical structure,easy modification of methoxy groups and electron-rich cavity,pillar[5]arene,as the simplest macrocyclic compound of pillararene,could interact with guests with neutral electricity,electronegativity and positive electricity via noncovalent interaction including cation???πinteraction,π???πinteraction,C-H???πinteraction,electrostatic interaction etc.to construct multifunctional supramolecular assemblies,and be gradually applicated to material science,nanotechnology and bioscience.Mechanically interlocked molecules（rotaxanes,catenanes,molecular knots and so on）which depend on the special steric structures and assembling methods,play an important role in molecular machines,organic catalysis,self-assembling,drug delivery,molecular recognitions and so on.Based on these,this thesis is mainly focused on the monofunctional pillararene based molecular machines with various functions and applications.Based on the easy modifications of pillararene,we synthesized monoester functionalized pillar[5]arene firstly and constructed pillar[5]arene based[1]rotaxane via further modifications.The traditional methods to construct[1]rotaxane include:a)prepare pseudo[1]rotaxane firstly and block the terminal group with stopper;b)prepare pseudo[2]rotaxane through host-guest interaction,then obtain the final[1]rotaxane through simple reaction to connect the guest and pillararene.Herein,we synthesized a kind of[1]rotaxane based on monoester functionalized pillararene and 1,8-octylenediamine firstly and the NMR analysis indicated that this chemical was very stable self-included structure in CDCl₃ and DMSO.After that,we prepared stable[1]rotaxane through condensation reaction with 6-aminocaproic acid and Birch reaction with 4-（N,N-diphenylamino）benzaldehyde.The steric assembled structure and corresponding characteristics were conducted through ¹H NMR、2D ¹H-¹³C HSQC、2D ¹H-¹H COSY、2D ¹H-¹H NOESY and ESI-MS analysis,and the results showed this[1]rotaxane was very stable to solvents and acid,which maybe due to the strong N-H???O and C-H???πinteraction between guest and pillar[5]arene.Because the structure of pseudorotaxane made of monoester functionalized pillar[5]arene and ethylenediamine showed different responsive abilities to the polarities of various solvents,we synthesized a pseudorotaxane modified by guest with positive charge based on monoester functionalized pillar[5]arene,ethylenediamine,1,8-dibromooctane and pyridine as starting materials,and studied the structural stability of this compound when dissolved in solvents with different polarities.The results showed this chemical could change the assembled formats from assembly to disassembly when increased the polarity of solvent.For example,this chemical occurred with pseudo[n]rotaxane in CDCl₃ and with free molecule in DMSO.Furthermore,this chemical can assemble into spherical vesicles when dissloved in THF and H₂O,and possessed ability of adsorption to cargo red through electrostatic interaction.Because of the strong host and guest interaction between pillar[5]arene with pyridine cation and triazole group,we synthesized a kind of mono guest functionalized pillar[5]arene with self-included structure and made of monohydroxyl pillar[5]arene,bromoacetylene,1-azido-8-bromooctane,4-pyridine boric acid and triphenylamine as the starting materials.This chemical displayed dynamic motion responsive to various solvents through the NMR analysis in CDCl₃,CD₃OD and DMSO and fluorescent experiments in CH₂Cl₂,CHCl₃,CH₃CN,DMF,DMSO and MeOH.The specific phenomena could be described as following:a)it is a self-included[1]rotaxane in CDCl₃ and pillar[5]arene is located near pyridine cation;b)it is a self-included[1]rotaxane in CD₃OD and pillar[5]arene is located far from pyridine cation;c)it is an free molecule in DMSO.The property of structural changes responsive to solvents not only realized the function of molecular machine but also had the potential values in design and applications of new molecular machines.