Abstract
The inclusion of azulene (AZ) inside the cavities of β-cyclodextrin (β-CD) and γ-cyclodextrin (γ-CD) was studied using absorption, fluorescence and induced-circular dichroism spectroscopy. The inclusion of AZ into the cavity of β-CD has a stoichiometry of 1:1, whereas that of AZ/γ-CD complex is 1:2. The equilibrium constants for the formation of the two complexes were calculated to be 780 ± 150 M-1 for AZ:β-CD and (4.5 ± 0.86) × 105 M-2 for AZ:(γ-CD)2. The latter is due to a stepwise equilibrium mechanism in which a 1:1 complex is formed with a binding constant of 775 M -1, followed by the formation of a 1:2 complex with a binding constant of 580 M-1. The difference between the two binding constant values is slight, indicating an almost equal contribution from each of the γ-CD molecules to the overall binding in AZ:(γ-CD)2. From the induced-circular dichroism spectra, the inclusion of AZ was found to be axial in AZ:β-CD and nearly axial in AZ:(γ-CD)2.
| Original language | English |
|---|---|
| Pages (from-to) | 245-251 |
| Number of pages | 7 |
| Journal | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy |
| Volume | 62 |
| Issue number | 1-3 |
| DOIs | |
| Publication status | Published - Nov 2005 |
Keywords
- Absorption
- Azulene
- Binding constant
- Circular dichroism
- Cyclodextrin
- Fluorescence
- Stoichiometry
ASJC Scopus subject areas
- Analytical Chemistry
- Atomic and Molecular Physics, and Optics
- Instrumentation
- Spectroscopy