Preparation And Host-Guest Chemistry Of High-Level Pillararenes

The arrival of any novel kind of macrocyclic hosts can significantly promote the development of supramolecular chemistry.Pillararenes,as a novel family of macrocyclic host molecules,have attracted growing interest since they were reported in 2008.Because of their rigid pillar architectures and ascendant host-guest properties,pillararenes have been demonstrated to be a key player in supramolecular chemistry over the past decade.As an important part of pillararene family,high-level pillararenes have unique topological structures and host-guest properties that are different from pillar[5]arenes and pillar[6]arenes.However,the study of these high-level pillararenes is not deep enough so far.In this thesis,we investigated the preparation of water-soluble pillar[7]arene and pillar[9]arene,their pH-responsive complexation with different guests and self-assembly in water based on the new molecular recognition motifs.The main content of the dissertation includes four parts as following:In the first part,we synthesized a water-soluble pillar[7]arene and investigated its pH-controlled complexation with paraqut in water.We demonstrated that the host and the guest formed a 1:1[2]preudorotaxane with a greatly high association constant of(2.96 ± 0.31)×109 M-1 mainly driven by multiple electrostatic interactions.Furthermore,we used this novel recognition motif to construct a supra-amphiphile based on water-soluble pillar[7]arene and an amphiphilic paraquat derivative.The supra-amphiphile self-assembled in water into supramolecular vesicles.In the second part,we synthesized a novel water-soluble pillar[9]arene and also studied its pH-responsive binding to paraquat guest.We found that the host and the guest formed a stable 1:1 inclusion complex in water with a considerably high association constant of(2.27±0.24)x 108 M-1.More interestingly,we demonstrated that the assembly and disassembly of this host-guest complex could be reversibly controlled by changing the solution pH.In the third part,we investigated a novel dual-pH responsive molecular recognition motif between water-soluble pillar[9]arene and 2,7-diazapyrenium salt.It was demonstrated that the host and the guest formed a stable 1:1 inclusion complex in water with an extraordinarily high association constant of(9.42±1.33)x 108 M-1.Furthermore,this host-guest complex can behave as a molecular switch that not only can be operated between its complexed and decomplexed states through the sequential addition of an acid and a base(HCl and NaOH,respectively)but also can be controlled upon the continual addition of a base and an acid(hexylamine and TFA,respectively).In the last part,we studied the pH-controlled host-guest complexation between water-soluble pillar[7]arene and 2,7-diazapyrenium salt.We demonstrated that the host and the guest formed a 1:1[2]preudorotaxane with a greatly high association constant of(7.14±0.38)×108 M-1.Moreover,we fabricated a novel supra-amphiphile based on water-soluble pillar[7]arene and an amphiphilic 2,7-diazapyrenium derivative.Different from the nanoparticles formed by the amphiphilic guest alone,the host-guest complex self-assembled into vesicles.Also,upon addition of acid/base,we could easily control the reversible transformation from nanoparticles to vesicles.