Spectroscopic studies on the inclusion complex formation between 7-iodo-8-hyroxyquinoline-5-sulfonic acid and β-cyclodextrin

Abstract

Formation of an inclusion complex between 7-iodo-8-hyroxyquinoline-5-sulfonic acid (IHQS) and β-cyclodextrin is studied by spectrophotometry and 1H NMR techniques. Spectral changes in the emission spectra upon the addition of β-cyclodextrin to IHQS in aqueous media were too small to allow for the determination of the binding constant. On the other hand; absorption spectra show a pronounced changes upon the addition of β-cyclodextrin that allowed for the determination of the binding constant. Absorption measurements show 1:1 inclusion of IHQS in the β-cyclodextrin cavity with an association constant of 135 ± 25 M−1. 1H-NMR studies are used to confirm the inclusion and to provide information about the geometry of IHQS inclusion in the cavity of β-cyclodextrin.