Study on the aggregation and electrochemical properties of Rose Bengal in aqueous solutions of cyclodextrin

The interactions of Rose Bengal (RB) with ?-cyclodextrin (?-CD), hydroxypropyl-?-cyclodextrin (HP-?-CD), hydroxypropyl-?-cyclodextrin (HP-?-CD), heptakis(2,3,6-tri-O-methyll)-?-cyclodextrin (TM-?-CD) were studied in aqueous solutions of 0.1 M KClO4 and 0.1 M LiClO4 by vis absorption, fluorescence spectroscopy as well as electrochemical measurements at 298 K. The spectrophometric results indicate that RB is included in all ?- and ?-CDs forming complexes with a stoichiometry 1:1 whose stability is slightly higher in KClO4 than in LiClO4 solutions. The complex stability constants determined for salt-containing CD solutions are lower than those for water solutions. The complexation of RB with ?- and ?-CD and the differences between the complexes obtained in the presence of the two salts were confirmed by an electrochemical study.