Host-Guest Complexations of Amine Boranes and Isoelectronic/Isostructural Quaternary Alkylammonium Cations by Cucurbit[7]uril in Aqueous Solution

The host-guest complexation of six amine boranes (R3NBH3) by the macrocyclic host molecule cucurbit[7]uril (CB[7]) in aqueous solution has been investigated using 1H and 11B NMR spectroscopy. The limiting complexation-induced 1H and 11B chemical shift changes indicate that the amine boranes are incl...

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Bibliographic Details
Published in:Heteroatom chemistry 2019-01, Vol.2019 (2019), p.1-7
Main Authors: Gamal-Eldin, Mona A., Macartney, Donal H.
Format: Article
Language:English
Subjects:
Amines
Ammonia
Aqueous solutions
Bond strength
Boranes
Chemical equilibrium
Competition
Complexation
Dipole interactions
Hydrogen
Hydrophobicity
Investigations
Molar volume
NMR
NMR spectroscopy
Nuclear magnetic resonance
Nuclear magnetic resonance spectroscopy
Quadrupole interaction
Quadrupoles
Spectrum analysis
Stability
Stability constants
Supramolecular compounds
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Summary:The host-guest complexation of six amine boranes (R3NBH3) by the macrocyclic host molecule cucurbit[7]uril (CB[7]) in aqueous solution has been investigated using 1H and 11B NMR spectroscopy. The limiting complexation-induced 1H and 11B chemical shift changes indicate that the amine boranes are included in the hydrophobic cavity of the host molecule. The host-guest stability constants for neutral R3NBH3∙CB[7] complexes (in the range of 105-107M-1) have been determined by 1H NMR competition experiments and are compared with the corresponding values for the isoelectronic/isostructural R3NCH3∙CB[7] + complexes. Ammonia borane (H3NBH3) does not form a host-guest complex with CB[7]. The trends in the host-guest stability constant with the guest molar volume are examined, and the stability is ascribed to the hydrophobic effect (packing coefficient) and quadrupole-dipole interactions.
ISSN:1042-7163
1098-1071
DOI:10.1155/2019/8124696