Study On Design And Properties Of [n]rotaxane Based On Pillar[5]arene

Rotaxane is one of the most popular types of mechanical interlocked molecules in these years.Because of its fascinating topological aesthetics and artificially controllable intermolecular movement between molecules,it has become a research hotspot for scientific researchers.Noncovalent bond forces are crucial for the construction of rotaxane.It is not only the main driving force for the formation of rotaxane,but also the key to its rich specific functions.Rings,shafts,and plugs are the three most important parts of a rotaxane.The shuttle streaming between the ring and the shaft of rotaxane can cause changes in the molecular physical or chemical properties,which brings the application prospect of rotaxane in molecular machines and information storage.Pillararene has been a research hotspot in the field of supramolecules for twelve years since its inception.At the same time,it has become an excellent choice for constructing(pseudo)rotaxanes due to its unique advantages such as highly symmetrical rigid skeleton,appropriately sized cavity,easy modification,simple synthesis,and strong host-guest recognition.In this paper,we designed and synthesized a series of various rotaxane structures based on pillar[5]arenes,including simple[1]rotaxane,complex[3]rotaxane,and new hybrid[1]/[2]rotaxanes.The impact of external interference stimuli on the structure of rotaxane were further explored.The main research contents are as follows:1.Symmetric axis guest molecules containing azobenzene and 1,2,3-triazole are synthesized by continuous substitution reaction and alkynyl-azide cycloaddition reaction.They undergo host-guest complexation with perethoxypillar[5]arenes through CH…N(O)and CH…? interaction.At last,the end capping reaction is used to construct[3]rotaxanes.The NMR results showed that different alkyl chain lengths in[3]rotaxanes would cause the relocation of the pillar[5]arenes on the guest.In addition,the cis-trans isomerization of azobenzeneunit in[3]rotaxanes and the relocation of pillar[5]arenes also be achieved by adjusting the wavelength of light.2.The mono-substituted pillar[5]arenes connecting the long chain with azobenzene and 1,2,3-triazole were prepared to construct a new type of asymmetric guest molecule.It has therecogination ability,to end-cap and to act as a host molecule.This kind of novel asymmetric guest molecules can be further complexed with perethoxypillar[5]arene togivenew hybrid[1]/[2]rotaxanes.This is a totally new kind of rotaxane,which opens up new rout for the future design of rotaxanes molecule3.The increase of hydrogen bonding sites in the molecule can directly enhance the strength of the complex.So,we used the ureidopyrimidone group with a unique quadruple hydrogen bonds to construct[1]rotaxane.By using ureidopyrimidone and mono-substituted aminopillar[5]arenes as axis and wheel,[1]rotaxanes were covneiently synthesized through nucleophilic substitution reaction.The length of the alkyl chain of pillar[5]arenes plays a key effect to the formation of[1]rotaxanes.Additionally,by adjusting thee polarity of solvents and adding other guest,the external respones to the structures of[1]rotaxanes were studied.4.By employing p-orm-phthaloyl chloride,potassium thiocyanate,and mono-substituted aminopillar[5]arenes as raw materials,the biacylthiourea bridged bis-pillar[5]arenes were prepared by one-pot two-step reaction under ultrasonic radiation.The length of alkyl chain in pillar[5]arene directly controlled formation of a covalent bonded simple bis-pillar[5]arenes or formation of noncovalent bond bis-[1]rotaxane.In addition,the introduction of acylthiourea also increased the recognition site and coordination ability of this macrocylic compounds with long coordination group.