Binding of 2-Acetylnaphthalene to γ-Cyclodextrin: Stoichiometry of the Dimer Complex

Abstract

Naphthalene derivatives have the capability of forming higher order complexes than the typical 1:1 stoichiometry with all three of the common cyclodextrins (α, β, and γ). The 2-acetylnaphthalene (2-AN)/γ-cyclodextrin (γ-CD) system exhibits a long wavelength fluorescence emission at higher γ-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/γ-CD or (2-AN)₂/(γ-CD)₂. Our analysis indicates that the latter formula is the correct one. This result is unanticipated, given the fact that a single γ-CD cavity could accommodate two naphthalene rings.

Keywords

Cyclodextrins 2-Acetylnaphthalene Guest:host complexes Dimers Fluorescence

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