Spectrofluorometric study of complexation of some amino derivatives of 9,10-anthraquinone with β-cyclodextrin

Complexation reactions between 1-amino-9,10-anthraquinone (AA1), 1-amino-2-methyl-9,10-anthraquinone (AA2), 1-amino-2,4-dimethyl-9,10-anthraquinone (AA3) and 1-amino-2-ethyl-9,10-anthraquinone (AA4) and β-cyclodextrin were studied spectrofluorometrically, under optimized experimental conditions. The formation constants of the resulting 1:1 β-cyclodextrin complexes were evaluated and found to decrease in the order AA4 > AA1 > AA3 > AA2. Possible reasons for the observed stability sequence are discussed based on the structures proposed for the resulting inclusion complexes.