NMR Investigations of Inclusion Complexes between β-Cyclodextrin and Naphthalene/Anthraquinone Derivatives |
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Authors: | Huiming Jiang Hongjie Sun Shubiao Zhang Ruinian Hua Yingmei Xu Shubin Jin Haiyan Gong Lin Li |
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Institution: | (1) Department of Chemical Engineering, College of Life Science, Dalian Nationalities University, Dalian, 11600, China |
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Abstract: | A 1H and 13C NMR study on the inclusion complex between β-cyclodextrin and naphthalene, 1,5-dichloronaphthalene and 9,10-anthraquinone
was carried out in order to define the stoichiometry of the association and the possible conformations. The upfield variation
of the chemical shifts from the protons locate inside the cavity (H-3, H-5) coupled with the downfield variation of the other
protons which locate outer sphere of the β-CD (H-1, H-2, H-4 and H-6,6′) provided clear evidence of the inclusion phenomena.
The NMR spectra revealed the formation of 1:1 inclusion complex in which aromatic ring of the guest is tightly held by the
host cavity. The signal degeneration of 1H & 13C NMR spectra still exist for naphthalene and 1,5-dichloronaphthalene upon complexation revealed a symmetrical conformation
of the guest molecules in the cavity of β-cyclodextrin, respectively. However, in 9,10-anthraquinone, the signal degeneration
of 1H & 13C NMR spectra was removed upon complexation which revealed an unsymmetrical conformation of the guest molecule inside the
cavity. According to theoretical calculations and NMR studies, the possible conformations of the inclusion complexes are given
here. |
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Keywords: | anthraquinone β -cyclodextrin inclusion complex naphthalene NMR |
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