Inclusion complexes of Rose Bengal and cyclodextrins

The interaction of Rose Bengal (RB) in aqueous solution with four different cyclodextrins, namely hydroxypropyl-β-cyclodextrin (HP-β-CD), hydroxypropyl-γ-cyclodextrin (HP-γ-CD), heptakis(2,6-di-O-methyl)-β-cyclodextrin (DIMEB), heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TRIMEB), was studied by spectrophotometric and calorimetric measurements. An original extension of the Benesi–Hildebrand treatment was proposed to evaluate the binding constants analysing spectrophotometric data. The results suggest that, at the concentration taken in exam, RB includes in all modified CDs considered forming complexes 1:1 with different stability depending on cavity size and kind of derivative.