X-Ray and NMR Studies on Host–Guest Inclusion Complex Formation between Crown Ethers and Pyridinium Compounds

Abstract

Inclusion complex formation between benzene-substituted crown ethers and electron-deficient pyridinium ions was studied by crystallographic and NMR methods. The major attractive host ± guest interactions in these complexes are face-to-face aromatic ± aromatic and cation ± p interactions. In addition, the crystal structures show that hydrogen bonding influences the complexation of cations. Individual studies of the binding strength as a function of host, guest, and solvent were carried out. Four pyridinium guests were prepared for the investigation. Fast atom bombardment (FAB) mass spectrometry was used to determine the stoichiometry of the complexes. The stability constants were measured by 1 H NMR and the structures of the complexes in acetonitrile are discussed. X-ray crystal structures were determined for complexes of dibenzo-18-crown-6 with pyridinium tetrafluoroborate (2 B18C 6 ± PyBF 4 ) and dibenzo-18-crown-6 with 1-aminopyridinium tetrafluoroborate (2 B18C 6 ± 1-NH 2 PyBF 4 ).

Stability of 1-naphthalenediazonium ion in solution. Complexation and decomposition of 1-naphthalene- diazonium tetrafluoroborate in the presence of crown ethers and acyclic polyethers in 1,2-dichloroethane and the gas phase under fast atom bombardment conditions

“…14,16,20,24,28,29 In the FAB-MS method the complex is first formed in the liquid matrix and is then analysed in the gas phase by mass spectrometry. Hence the complex must exist both in solution and in the gas phase.…”

Molecular motion in pyridazinium/crown ether supramolecular cation salts of a nickel dithiolene complex

“…It is known that protonated cations of six-membered heteroaromatic rings can form supramolecular structures with crown ethers. 13 By complexing monoprotonated pyridazinium cations with [18]-crown-6, the N-H + part will 30 interact with the oxygen atoms in [18]-crown-6 through hydrogen bonding, forming a supramolecular rotator structure. The pyridazinium cation may exhibit flip-flop motion across the rotational axis along the hydrogen bond.…”

Crown Ether/Carbon Nanotubes Based Biperiden Disposable Potentiometric Sensor

“…The size of the crown ether cavity is crucial and better sensitivity and selectivity is to be expected for cavity size sterically matching the gust molecules to be sensed . Crown ethers are able to form stable complexes not only with metal cations but also with ammonium cation and protonated amines .…”

“…Crown ether forms inclusion complexes with biperiden (Scheme ) through piperidin ring similar to that with pyridinium compounds . Such binding event creates the phase boundary potential at the membrane–sample interface.…”