INCLUSION COMPLEXES OF SOME 3H-INDOLES WITH CYCLODEXTRINS STUDIED THROUGH EXCITED-STATE DYNAMICS AND STEADY-STATE ABSORPTION AND FLUORESCENCE SPECTROSCOPY

We present a steady state and time-resolved fluorescence study of two 3H-indole molecules, namely 2-[(p-amino)phenyl]-3,3-dimethyl-5-cyano-3 H-indole (1) and imethylamino)phenyl]-3,3-dimethyl-5-cyano-3Hindole (2 ) in aqueous solutions of alpha-,beta- and gamma-cyclodextrins. The st oichiometries and association constants of the molecules have been ass essed in the different cyclodextrin (CD) systems. The spectral charact eristics, bandwidths and association constants show that molecule 2 ex periences a stronger interaction with the host CDs than molecule 1. St eady state fluorescence experiments show the presence of only one kind of complex for the molecules in alpha- and gamma-CDs, whereas time-re solved fluorescence measurements and global analysis reveal the presen ce of two kinds of complex, thereby demonstrating the higher sensitivi ty of the time-resolved experiments. Fluorescence quenching is observe d for both molecules in gamma-CD, whereas in alpha- and beta-CDs fluor escence enhancement is found. This has been correlated with the lower quantum yield of the complex in the former case. The observations of f luorescence quenching, together with the magnitudes of the association constants, show that the molecules form different complexes with gamm a-CD compared with alpha- and beta-CDs.