Spectroscopic studies of inclusion complexes of methyl-p-dimethylaminobenzoate and its ortho derivative with α- and β-cyclodextrins.

The effects of α- and β-cyclodextrins (CDs) on the both emission modes (LE -locally excited and TICT -twisted intramolecular charge transfer) of the fluorescence spectrum of methyl-p-dimethylaminobenzoate (I) and its o-methoxy (II) derivative in aqueous solution have been investigated using steady-state and time-resolved fluorescence techniques. It is found that the intensity of both fluorescence bands increases with increasing concentration of α- and β-CD. The stoichiometries and equilibrium constants of the fluorophore-cyclodextrin inclusion complexes have been determined by steady-state fluorescence measurements. Performed spectroscopic studies demonstrate that in the case of I in α-CD and β-CD, both 1:1 and 1:2 inclusion complexes are formed, whereas only 1:1 inclusion complex is formed between II and β-CD.