Interactions between a surface-active cationic 3H-indole molecular probe and beta-cyclodextrin. Design of a novel type of rotaxane

We report herein the interactions of a cationic surface-active molecular pr obe having long aliphatic chains, i.e., iodo-methyldioctadecyl 2-( p-hexyla minophenyl)-3,3-dimethyl-5-carboethoxy-3H-indole ammonium, with beta-CD inv estigated by spectral and photophysical characterizations. It is found thro ugh lifetime measurements that only two species exist within the whole rang e of beta-CD concentrations. Both the steady-state and the time-resolved fl uorescence results further show that the stoichiometry of the inclusion com plex is 1:3. It is also suggested that an interaction of the aliphatic chai ns of the cationic 3H-indole with beta-CD takes place. Finally it is shown that a new rotaxane forms spontaneously in solution. (C) 1999 Elsevier Scie nce B.V. All rights reserved.