Inclusion complexes of naphthalimide derivatives with cyclodextrins

Complex formation between naphthalimide derivatives (2,3- and 1,8-naphthalimides and their respective N-butyl derivatives) and alpha-, beta- and gamma-cyclodextrins (CDs) was studied by UV and fluorescence spectroscopy. All the naphthalimides studied form 1:1 inclusion complexes with beta- and gamma-CDs, and the corresponding binding constants were determined. For beta-CD complexes, the data obtained suggest a relatively tight axial inclusion of 2,3-naphthalimides and an equatorial inclusion of 1,8-naphthalimides. In contrast, for the gamma-CD complexes, the data indicate a loose fit of the naphthalimides within the cavity. A remarkable exception is 2,3-N-butylnaphthalimide, which forms an unusually tight inclusion complex with gamma-CD. In this complex, the quenching of the naphthalimide fluorescence by bromide ion is fully prevented. (C) 1997 Elsevier Science S.A.