Abstract
Steady-state fluorescence has been used to study the inclusion complexes of 2-methylnaphthoate (MN) with α- and β-cyclodextrins (CDs). Emission spectra of MN show two bands that are very sensitive to the CD concentration and temperature. The stoichiometry and formation constants of these complexes were investigated by obtaining the ratio of the two bands. Results showed identical stoichiometry (1:1) for both MN/α-CD and MN/β-CD complexes. However, the estimated formation constants were quite different. The thermodynamic parameters ΔH and ΔS were obtained from vant'Hoff plots. Results showed that MN/α-CD complexation is accompanied by an high enthalpy change, while MN/β-CD complexation is mainly en tropically favored. Anisotropy measurements were used to interpret the different signs of ΔS upon inclusion for both complexes. In addition, 2-methylnaphthoate seems to be a good probe for estimating microenvironmental polarity. Effective dielectric constants of inner α- and β-CD cavities were evaluated.
Keywords
Get full access to this article
View all access options for this article.
