γ-Cyclodextrin induced intermolecular excimer formation of thioflavin T

The excimer emission of thioflavin T, 3,6-dimethyl-2-(4-dimethylaminophenyl)-benzothiazolium cation (TFT+), was observed in the presence of γ-CD at room temperature. The emission intensity initially decreased due to the formation of a 2:1 TFT+-γ-CD inclusion complex. At higher concentrations of γ-CD an increase in the emission intensity was observed due to the formation of a 2:2 TFT+-γ-CD inclusion complex. The formation of the 2:2 TFT+-γ-CD inclusion complex was responsible for the excimer emission. In the presence of β-CD, the TFT+ molecule did not show excimer emission. The excimer emission observed in the presence of γ-CD was analysed by excitation and 3-D spectral measurements.