Inclusion complexation of ?-cyclodextrin and 6-O-?-�maltosyl- and 2-O-(2-hydroxypropyl)-?-cyclodextrins �with some fluorescent dyes

Abstract

Spectrofluorimetric titrations were performed in aqueous phosphate buffer (pH 7.20, 0.1 mol dm ˇ3 )t o determine the binding constants of b-cyclodextrin (1), mono(6-O-a-maltosyl)-b-cyclodextrin (2) and mono(2-O-(2- hydroxypropyl))-b-cyclodextrin (3) with four fluorescent dyes, ammonium 8-anilino-1-naphthalenesulfonate (ANS), sodium 2-(p-toluidino)naphthalene-6-sulfonate (TNS), Acridine Red (AR) and Rhodamine B (RhB). The fluorescence of ANS, TNS and AR were enhanced, whereas that of RhB was quenched, by the inclusion complexation with b-cyclodextrin hosts 1-3. It was found that the binding ability of the three cyclodextrin hosts generally decreases in the order 1> 3> 2, which indicates that the hydrophobicity of the substituent affects the original binding ability of parent b-cyclodextrin to some extent. On the other hand, the size, shape and charge of the guest are the crucial factors which dominate the stability of the supramolecular complex formed. Copyright © 2000 John Wiley & Sons, Ltd.