title: Cucurbit[7]uril host-guest complexes and [2]pseudorotaxanes with N-methylpiperidinium, N-methylpyrrolidinium, and N-methylmorpholinium cations in aqueous solution.
abstract: The formations of host-guest complexes between cucurbit[7]uril and a series of N-substituted N-methylpiperidinium, N-methylpyrrolidinium, and N-methylmorpholinium cations in aqueous solution have been investigated using (1)H NMR spectroscopy and electrospray ionization mass spectrometry. Dications comprising the N-methylheterocyclic head groups, bridged by a decamethylene chain, form sequential 1 : 1 ([2]pseudorotaxanes) and 2 : 1 host-guest complexes with cucurbit[7]uril. The cucurbituril initially resides over the decamethylene chain, however with further additions of the host molecule a translocation of the hosts to the cationic N-heterocyclic head groups occurs. The order of the magnitude of the cucurbituril host-guest stability constants, determined by competitive (1)H NMR binding experiments, follows the trend in the hydrophobicity of the quaternary ammonium cations.
authors: Department of Chemistry, Queen's University, 90 Bader Lane, Kingston, ON K7L 3N6, Canada.
authors: Mona A
authors: MA
authors: Gamal-Eldin
authors: Donal H
authors: DH
authors: Macartney
mesh_terms: D001952:Bridged-Ring Compounds / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D007093:Imidazoles / Q000737:chemistry*; D015394:Molecular Structure; D009025:Morpholines / Q000737:chemistry*; D010880:Piperidines / Q000737:chemistry*; D011759:Pyrrolidines / Q000737:chemistry*; D043862:Rotaxanes / Q000737:chemistry*; D012996:Solutions; D014867:Water / Q000737:chemistry; D047028:Macrocyclic Compounds; D000099246:Cucurbit(n)urils
chemical_list: D001952:Bridged-Ring Compounds; D002412:Cations; D007093:Imidazoles; D009025:Morpholines; D010880:Piperidines; D011759:Pyrrolidines; D043862:Rotaxanes; D012996:Solutions; D014867:Water; C456276:cucurbit(7)uril; D047028:Macrocyclic Compounds; D000099246:Cucurbit(n)urils