X-RAY AND NMR-STUDIES ON HOST-GUEST INCLUSION COMPLEX-FORMATION BETWEEN CROWN-ETHERS AND PYRIDINIUM COMPOUNDS

Inclusion complex formation between benzene-substituted crown ethers a nd electron-deficient pyridinium ions was studied by crystallographic and NMR methods. The major attractive host-guest interactions in these complexes face-to-face aromatic-aromatic and cation-pi interactions. In addition, the crystal structures show that hydrogen bonding influen ces the complexation of cations. Individual studies of the binding str ength as a function of host, guest, and solvent were carried out. Four pyridinium guests were prepared for the investigation. Fast atom bomb ardment (FAB) mass spectrometry was used to determine the stoichiometr y of the complexes. The stability constants were measured by H-1 NMR a nd the structures of the complexes in acetonitrile are discussed. X-ra y crystal structures were determined for complexes of dibenzo-18-crown -6 with pyridinium tetrafluoroborate (2B18C6-PyBF4) and dibenzo-18-cro wn-6 with 1-aminopyridinium tetrafluoroborate (2B18C6-1-NH2PyBF4).