Naphthalene derivatives have the capability of forming higher order complexes than the typical 1:1 stoichiometry with all three of the common cyclodextrins (alpha, beta, and gamma). The 2-acetylnaphthalene (2-AN)/gamma-cyclodextrin (gamma-CD) system exhibits a long wavelength fluorescence emission at higher gamma-CD concentrations, which has been assigned to an excimer band from bound 2-AN dimer. On the basis of the fact that only free 2-AN and the bound dimer fluoresce in this system, we have proposed mathematical models to decide whether the dimer formula is (2-AN)2/gamma-CD or (2-AN)2/(gamma-CD)2. Our analysis indicates that the latter formula is the correct one. This result is unanticipated, given the fact that a single gamma-CD cavity could accommodate two naphthalene rings.
Ji Hyun LaRose and T. C. Werner, "Binding of 2-Acetylnaphthalene to gamma-Cyclodextrin: Stoichiometry of the Dimer Complex," Appl. Spectrosc. 54, 284-286 (2000)