Kinetic Determination of Binding Constants for Cyclodextrin Inclusion of pada in Solution

Abstract

Competition kinetics was used to determine the binding constants of the dye pyridine-2-azo-p-dimethylaniline ( pada ) with β- cyclodextrin (β-CD), γ- cyclodextrin (γ-CD), 2,6-O-dimethyl-β-cyclodextrin ( dmβ ), 2,3,6-O-trimethyl-β-cyclodextrin ( tmβ ) and hydroxypropyl-β-cyclodextrin ( hpβ ) at 25.0°. Stopped-flow spectroscopy was used to monitor the change in kinetics after cyclodextrins had been added to the Ni_aq²⁺ and pada reactant solutions. The values of the binding constants/dm³ mol-¹ with pada were 300 for β-CD, 40 for γ-CD, 550 for dmβ, 210 for tmβ , and 350 for hpβ.