Study On Supramolecular Pseudorotaxanes Comprising Nitrogen Cations And Dibenzo-24-Crown-8 Ether

Molecular recognition and self-assembly of crwon ether, especially dibenzo-24-crown-8 (DB24C8) has been one of current important topics in supramolecular chemistry. To further deepen understanding of available recognition motifs and to make the best of kown recognition motifs for supramolecular architectures, a series of guests containing positively charged nitrogen center(s) were synthesized and their binding abilities to DB24C8 were investigated. Also, the crystal structures of some complexes with DB24C8 and their self-assemblies in the solid state were explored in detail by X-ray single crystal diffraction.1. Mono- and diprotonated 4,4′-bipyridine were prepared. And their binding behaviors with DB24C8 were examined by UV-vis absorption spectra, ESI-mass spectra and 1H NMR spectra. Association constants between these two guests and DB24C8 were determined respectively. Furthermore, the complex of monoprotonated 4,4′-bipyridine with DB24C8 was characterized by X-ray diffraction, and its self-assembly in the solid state was investigated.2. Five novel 1,2-bis(N-acylaminopyridinium)ethane derivatives were prepared. Effects of acylation of the terminal amino groups on the association abilities with DB24C8 were investigated using 1H NMR spectra and X-ray diffraction, and the association constants of some complexes were determined by the single spot method. The results indicated that acylation can enhance their binding abilities and also affects their crystal structures and self-assemblies.3. Four novel 1,2-bis(pyridinium)ethane derivatives containing acylamide or acylhydrazine groups were synthesized. Effects of the introduction of these groups were explored by means of 1H NMR spectra and X-ray diffraction. The findings showed these groups, which can act as both of hydrogen-bonding donors and receptors, dramatically affected the self-assemblies of [2]pseudorotaxanes between these derivatives and DB24C8.4. The dication 1,2-bis(isoquinolinium)ethane was prepared. Effect of the incorporation of fused heterocycle on the binding ability was investigated by virtue of 1H NMR spectra and X-ray diffraction. The study suggested that the resulting guests have a similar capability to interact with DB24C8 whether the phenyl group is fused or directly attached as a substituent at the pyridinium ring. Furthermore, an unusual phenomenon that the aryl oxygen atoms exhibit shorter H…O distances than their alkyl counterparts was observed.5. Four secondary dialkylammonium with a pyridine ring as terminal groups were synthesized. The binding behaviors of these guests to DB24C8 were analyzed based on the 1H NMR spectra and X-ray diffraction. The results revealed that the interaction between the secondary ammonium and DB24C8 was augmented by replacement of phenyl groups with pyridinyl rings and that protonation of terminal pyridine groups essentially affected the crystal structures and completely changed the self-assembly in the solid state.