Excimer formation in inclusion complexes of ß-cyclodextrin with salbutamol, sotalol and atenolol: spectral and molecular modeling studies.

The inclusion complexation behavior of salbutamol, sotalol and atenolol drugs with ß-cyclodextrin (ß-CD) were investigated by UV-visible, fluorometry, time resolved fluorescence, FT-IR, (1)H NMR, SEM and PM3 methods. The above drugs gave a single emission maximum in water where as dual emission in ß-CD. In ß-CD solutions the shorter wavelength fluorescence intensity was regularly decreased and longer wavelength fluorescence intensity increased. Addition of ß-CD to aqueous solutions of drugs resulted into excimer emission. The excimer emission is concluded to be due to a 1:2 inclusion complex between ß-CD and drug. Nanosecond time-resolved studies indicated that all drugs exhibited biexponential decay in solvents and triexponential decay in CD. Investigations of thermodynamic and electronic properties confirmed the stability of the inclusion complex.