Selective binding of chiral molecules of cinchona alkaloid by beta- and gamma-cyclodextrins and organoselenium-bridged bis(beta-cyclodextrin)s |
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Authors: | Liu Yu Li Li Zhang Heng-Yi Fan Zhi Guan Xu-Dong |
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Affiliation: | Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, PR China. yuliu@public.tpt.tj.cn |
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Abstract: | The inclusion complexation behavior of chiral members of cinchona alkaloid with beta- and gamma-cyclodextrins (1 and 2) and 6,6(')-trimethylenediseleno-bridged bis(beta-cyclodextrin) (3) was assessed by means of fluorescence and 2D-NMR spectroscopy. The spectrofluorometric titrations have been performed in aqueous buffer solution (pH 7.20) at 25.0 degrees C to determine the stability constants of the inclusion complexation of 1-3 with guest molecules (i.e., cinchonine, cinchonidine, quinine, and quinidine) in order to quantitatively investigate the molecular selective binding ability. The stability constants of the resulting complexes of 2 with guest molecules are larger than that of 1. As a result of cooperative binding, the stability constants of inclusion complexation of dimeric beta-cyclodextrin 3 with cinchonidine and cinchonine are higher than that of parent 1 by factor of 4.5 and 2.4, respectively. These results are discussed from the viewpoint of the size-fit and geometric complementary relationship between the host and guest. |
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Keywords: | Inclusion complexation Chiral molecule Cinchona alkaloid Cyclodextrins Fluorescence 2D-NMR Stability constants Molecular recognition Cooperative binding Organoselenium |
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