Excimer formation in inclusion complexes of β-cyclodextrin with salbutamol, sotalol and atenolol: Spectral and molecular modeling studies

The inclusion complexation behavior of salbutamol, sotalol and atenolol drugs with β-cyclodextrin (β-CD) were investigated by UV–visible, fluorometry, time resolved fluorescence, FT-IR, 1H NMR, SEM and PM3 methods. The above drugs gave a single emission maximum in water where as dual emission in β-CD. In β-CD solutions the shorter wavelength fluorescence intensity was regularly decreased and longer wavelength fluorescence intensity increased. Addition of β-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 β-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.

The energy minimized structures for the inclusion complexes between drugs and β-CD, (a) salbutamol, (b) sotalol and (c) atenolol.Figure optionsDownload as PowerPoint slideHighlights
► Addition of β-CD to aqueous solutions of salbutamol, sotalol, atenolol resulted in observation of excimer emission of each drug.
► The excimer emission is concluded to be due to a 1:2 β-CD:drug inclusion complex.
► Triexponential decay observed in nanosecond time-resolved fluorescence.
► Thermodynamic calculations confirm the better stability of the inclusion complex.
► Nanomaterial structural changes proved the formation of a inclusion complex.