Influence of the Cyclodextrin Size Cavity in the Complexation of Tetrahydroharmane

The interactions between cyclodextrins and tetrahydroharmane, 1-methyl-1,2,3,4-tetrahydro-9H-pyrido/3,4-b/indole, have been investigated in pH 10.1 aqueous media. Absorption and fluorescence studies, together with lifetime measurements show that tetrahydroharmane forms ground state inclusion complexes with -CD and -CD but not with -CD. Steady state experiments detect only one kind of tetrahydroharmane--CD complex, whereas time resolved measurements reveal the existence of two different types of 1:1 association complexes. The results in -CD are very similar to those in -CD, but the interactions are much weaker.