Title: Inclusion Complex of Fluorescent 4-Hydroxycoumarin Derivatives with Native β-Cyclodextrin: Enhanced Stabilization Induced by the Appended Substituent
Abstract: This work studies the interaction of substituted coumarins with β-cyclodextrin (β-CD). The role of the substituent in the 3 position was investigated. The guest molecules were two original 4-hydroxycoumarin derivatives, bearing an ethyl furoate (1) or a benzodioxanyl (2) substituent in the 3 position. Comparison was made with a nonsubstituted analogue (3). It must be noted that molecules 1 and 2 potentially offer very different complexation sites. Formation of the inclusion complex was checked by UV/vis absorption and fluorescence spectroscopy. A strong revival of the fluorescence intensity of 1 and 2 was observed in the presence of β-CD and partly attributed to the fact that the heterocyclic substituent was prevented from rotating freely. The 1:1 stoichiometry of the complex was established, and the values of the binding constants (7 × 102 and 3.4 × 102 M-1 for 1 and 2, respectively) were extracted from the spectrophotometric data. A much lower (8.1 × 101 M-1) binding constant was found for unsubstituted compound 3. The 1H NMR study confirmed that the coumaryl ring system was engulfed in the cyclodextrin cavity. The proximal moiety of the heterocyclic substituent also interacted with the β-CD, whereas the rest protruded outside the cavity. This explains that the substituent controls the structure of the inclusion complex and contributes to its stabilization.
Publication Year: 2001
Publication Date: 2001-10-02
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 37
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