Crown Ether Complexes of Six-Membered N-heteroaromatic Cations |
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Authors: | Sari Kiviniemi Maija Nissinen Tanja Kolli Jorma Jalonen Kari Rissanen Jouni Pursiainen |
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Institution: | (1) Department of Chemistry, University of Oulu, P.O. BOX 3000, FIN-90014 University of Oulu, Finland;(2) Department of Chemistry, University of Jyväskylä, P.O. BOX 35, FIN-40351 Jyväskylä, Finland. E-mail |
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Abstract: | Crown ether complexes of six-membered N-heteroaromatic cations and the closely related bicyclic purinium cation (6) have been studied by 1H NMR, mass spectrometric and crystallographic methods. The stability constants for the complexes were determined by 1H NMR titration in acetonitrile solution and the complexation stoichiometry by 1H NMR and ESI mass spectrometric methods. Altogether six crystal structures of complexes were determined to study the complexation in the solid state. Hydrogen bonding was observed to be the most important interaction for the complexation both in solution and in the solid state but – interactions also contribute to it. All crystal structures of the DB18C6 complexes with six-membered N-heteroaromatic cations, except for 4-hydroxypyridinium, are isomorphous to previously studied five-membered N-heteroaromatic cations and pyridinium complexes. Such a close resemblance is not observed in B18C6 and 18C6 complexes or DB18C6purinium (6). |
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Keywords: | N-heteroaromatic cations crown ethers host– guest chemistry non-covalent interactions |
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