Cyclodextrin Inclusion Complexes of 1-Pyrenebutyrate: The Role of Coinclusion of Amphiphiles

Article abstract of DOI:10.1021/ja00272a022

Several inclusion complexes with various stoichiometries are formed from 1-pyrenebutyrate ion (P) and the different cyclodextrins (α-, β-, and γ-CD).With α- and β-CD, the initially formed 1:1 complexes lead to the formation of 1:2 complexes (P*α2 and P*β2).As P can be only partially included in the small cavity of α-CD, the equilibrium constants for the formation of both complexes of α-CD are about an order of magnitude smaller than those of β-CD.For the same reason, P*β2, to which we assign a "barrel" configuration, is also an order of magnitude more effective than P*α2 in protecting singlet-excited P against quenching by triethanolamine.We had shown earlier that with γ-CD the 1:1 complex (P*γ) dimerizes to a 2:2 complex (P2*γ2), to which we also assigned a barrel configuration.The lack of efficient 1:2 complex formation in this case is attributed to the large size of the "barrel" enclosed by two γ-CD molecules.The extra space next to a single P molecule in such a cavity would have to be filled with water.However, the formation of a 1:2 inclusion complex between P and γ-CD can be induced by the coinclusion of a molecule with a hydrophobic moiety such as sodium hexanesulfonate (X).This replaces the water within the cavity and leads to the formation of P*X*γ2.This complex provides the highest degree of protection against quenching of excited P in these inclusion complexes.