Interaction of 6-p-Toluidinylnaphthalene-2-sulfonate with α-Cyclodextrin

The interaction of 6-p-toluidinylnaphthalene-2-sulfonate (TNS) with α-cyclodextrin was investigated in a 0.1 M phosphate buffer at pH 7.4 by fluorescence spectrophotometry. Using the fact that the fluorescence intensity of TNS increases in the presence of α-cyclodextrin, the thermodynamic parameters for the inclusion complex formation were determined as follows; ΔG°=-2.21 kcal/mol at 25°C, ΔH°=-3.0 kcal/mol, ΔS°=-2.6 e.u. The driving force for the inclusion complex formation was considered to be the van der Waals-London dispersion force and hydrogen bonding between the nitrogen atom of TNS and the secondary hydroxyl groups of α-cyclodextrin.Also, from the measurements of proton nuclear magnetic resonance spectra and the model building with Corey Pauling koltum models, the most probable structure was determined.