Copillararenes And Constitutional Isomers Of Pillararenes

Construction of functional molecular aggregates with well-defined supra-structure based on noncovalent interactions has attracted more attention from supramolecular chemists and the industry field in recent years. It is of continuing interests to design and prepare macrocyclic molecules because of their important roles to promote the development of supramolecular chemistry. Pillararenes are a new kind of cyclic oligomers made up of hydroquinone or hydroquinone ether derivatives which are connected by methylenes at para-positions. Because of their special structure and excellent host-guest properties, pillararenes have been emerging as the next generation of macrocyclic hosts after crown ethers, cyclodextrins and calixarenes. Since the first paper published in2008, pillararenes have been focus of supramolecular chemistry over the past few years. This dissertation is mainly about preparation of copillar[5]arenes, constitutional isomers of asymmetric pillar[5]arenes, their host-guest properties, self-assembly and porous material based on pillar[5]arene.The highly symmetrical structures of pillararenes make them difficult to selectively functionalize, which limiting their applications as novel macrocycles on some level. To control the selective functionalization, we synthesized few copillararenes, which are pillararenes containing different repeating units. Moreover, we found that we could control the main product of the co-oligomerization by changing the portion of different monomers. We also got some single crystal structures of these copillar[5]arenes. In one of them, there is an n-hexane molecule symmetrically included in the cavity of pillar[5]arene, forming a [2]pseudorotaxane in the solid state. The main driving forces are multiple C-H…π interactions according to the crystal structure of their complex.In the second part, we thought that if we incorporate a long alkyl chain group as the guest part into a pillar[5]arenes to form a AB type monomer. We should obtain linear supramolecular polymers from their self-organization in solution. By combination of various techniques, including1H NMR, DOSY, NOESY and viscometry at different temperatures, it was demonstrated that the formation of the supramolecular polymer is highly dependent on the temperature and monomer concentration. Moreover, rodlike fibers were drawn from a high concentration solution and observed by SEM, directly providing evidence for the formation of a supramolecular polymer with high molecular weight. Its crystal structure revealed that the aggregation of copillararene monomer to form a linear supramolecular polymer was driven by the quadruple C-H…π interactions, coupled with the entropic effect of desolvation of the host cavity.In the third part, we incorporated a10-bromodecyl group into a pillar[5]arene which could self-assemble into cyclic dimers both in solution and in the solid state. From X-ray single crystal analysis, we found that the dimerization was caused by van der Waals forces between the exo cavity parts of the decyl groups. This research provides a facile approach to control the self-assembly manner of self-complementary copillar[5]arene monomers between cyclic dimers and linear supramolecular polymers.In the fourth part, a solvent-driven doubly threaded [2]rotaxane dimer based on an amino-modified copillar[5]arene was prepared using bis(trifluoromethyl)phenyl isocyanate as stoppers. By comparison of proton NMR spectra of the rotaxane dimer and the model compound, the inclusion-induced shielding effects of the decyl protons of the dumbbell compound were estimated. Based on this, the length of the rotaxane dimer can be calculated. In CDC13, it was in a contracted state with a length of31A. In DMSO-d6, it was in an extended state with a length of37A. Moreover, as the polarity of the solvent changes, the length of this rotaxane dimer can change continuously.In the fifth part, four constitutional isomers of an nonsymmetric pillar[5]arene (BMpillar[5]arene) were prepared from an nonsymmetric monomer (1-butoxy-4-methoxybenzene) in an one-pot reaction and successfully separated by column chromatography. Except for the same molecular weight, all of the other properties of the four isomers we have investigated are more or less different. They have different melting points, different NMR spectra, different crystal structures, different stacking patterns in the solid state and different binding abilities with n-octyltrimethyl ammonium hexafluorophosphate (OTMA).In the last part, a porous material based on a carboxylic-acid pillar[5]arene and ploy(ionic liquid) was prepared. The pore characteristics of this supramolecular cross-linked porous material was investigated by nitrogen sorption measurements. The specific surface area calculated from the Brunauer-Emmett-Teller equation is 350m2/g. The pore volume calculated from the Barrett-Joyner-Halenda method is1.22cc/g. This porous material kept the pillar[5]arene’s host-guest property in solid state which makes it could absorb1,6-hexanediol in chloroform4.6times more than just using the carboxylic-acid pillar[5]arene. This absorption process could be finished in about one hour. The porous material showed different sorption ability for different substrates. For example, this material cannot absorb cyclohexanol and tert-butanol from chloroform at all.