SPECTRAL AND PHOTOPHYSICAL STUDIES OF THE 1 3 (GUEST/HOST) ROTAXANE-LIKE INCLUSION COMPLEX FORMED BY A 3H-INDOLE AND BETA-CYCLODEXTRIN/

In the present paper, we report a new type of rotaxane-like inclusion complex, i.e., the 1:3 (guest/host) type formed by iodotrimethyl 2-(p- hexylaminopheny1)-3,3-dimethyl- 5-carboethoxy-3H-indole ammonium (I), a fluorescent cationic surfactant, and beta-cyclodextrin (beta-CD). Th e time-resolved fluorescence measurement reveals that only two species of 1 exist within the whole range of beta-CD concentrations. Both the steady-state and the time-resolved fluorescence results show that the stoichiometry of the inclusion complex is 1:3. The urea effect on the formation of the inclusion complex has been investigated. It was foun d that the 1:3 inclusion complex is still formed in the presence of 3 M urea, while the association constant is markedly reduced. This sugge sts the hydrophobic nature of the interaction of 1 with either beta-CD or urea.