Host-Guest Chemistry Based On Bis (Meta-phenylene)-32-crown-10 And Dibenzo-24-crown-8 Derivatives

The host-guest chemistry based on crown ethers and their derivatives is an important research aspect in current supramolecular chemistry. The preparation efficiency of threaded structures is strongly dependent on the complexation strength of the host-guest system. Chemists have devoted numerous efforts into developing new recognition systems which exhibiting even stronger complexation strength. By comparison, the functional derivation of the known hosts or guests is a simple and efficient method for the promotion of complexation strength of the host—guest systems. Based on a systematic retrospect of the work that have been done in this research field, we chose the host-guest systems that based on bis(meta-phenylene)-32-crown-10 and dibenzo-24-crown-8 as the main research objects and improved the complexation of these crown ethers with some guests by the method of introducing ion-pair recognition. We also have further studied the application of these improved systems in preparing more complicated supramolecular systems such as rotaxane-based molecular machines and supramolecular polymers. The content of this dissertation includes the following five parts.First, we have introduced a urea unit onto dibenzo-24-crown-8, which usually bind only secondary ammonium, to furnish a receptor possessing ion-pair recognition ability. We demonstrated not only that the complexation between dibenzo-24-crown-8 derivatives and dibenzylammonium salts can be improved but also that the improvement can be tuned by controlling the electron density of the phenyleneurea group indirectly.We further used the ion-pair recognition to improve the complexation of bis(meta-phenylene)-32-crown-10 with paraquat. The resulting bis(meta-phenylene)-32-crown-10 derivative exhibited better complexation strength for paraquat compared to that of the simple bis(meta-phenylene)-32-crown-10. Even a Ka increase up to 219 times was observed. This improvement is controlled by not only the solvent polarity but also the nature of the anion. Furthermore, it was found that the structure of the complex is anion-controlled in the solid state. The host-guest complex is a pseudorotaxane in the solid state when the two counterions of paraquat are trifluoroacetate anions while it is a taco complex when the two counterions are hexafluorophosphate or chloride anions. This provided us a new way to control the host-guest complexation geometry.A series of bis(meta-phenylene)-32-crown-10 cryptands possessing ion-pair recognition ability were synthesized and their complexation with paraquat was studied. By adjusting the space of the cavity of the host through changing the length of the ethyleneoxy chain, we obtained the one that exhibited binding selectivity toward paraquat and N,N'-dimethyl-2,7-diazapyrenium salt. The reversible selective binding process is anion-controlled and can be switched by adding chloride or removal of it. This provides a new way to design novel contrable molecular machine.By combination of the binding ability of crown ethers and the unique properties of the metal-organic assemblies, we prepared three bis(m-phenylene)-32-crown-10-based discrete rhomboids by coordination-driven self-assembly and studied their complexation with paraquat. The neutral rhomboid exhibited an enhanced affinity for paraquat compared with simple bis(m-phenylene)-32-crown-10 while no complexation was observed between the cationic rhomboids and paraquat. It was demonstrated that metal-coordination could be used to control the binding of the bis(m-phenylene)-32-crown-10 to paraquat.Considering the strong binding strength that provided by the anion-assisted complexation of cation, we designed and prepared the water soluble anionic bis(m-phenylene)-32-crown-10 derivatives and studied their complexation with paraquat chloride. The affection of distribution location of the negative charges was also studied. Based on these studies, we synthesized a water soluble AB-type monomer and preliminaryly studied its self-assembly behavior in water.