title: γ-Cyclodextrin modulates the chemical reactivity by multiple complexation.
abstract: Multiple complexation by γ-CD has been studied by self-diffusion coefficients (DOSY) and chemical kinetics experiments in which 4-methoxybenzenesulfonyl chloride (MBSC) solvolysis was used as a chemical probe. The addition of a surfactant as a third component to the reaction mixture induced a very complex reactivity pattern that was explained on the basis of multiple complexation phenomena and surfactant self-assembly to form micelles. A cooperative effect that yielded a ternary complex formed by cyclodextrin-surfactant-MBSC was observed. The larger cavity of γ-CD in comparison with β-CD is responsible for the change from the competitive complexation mechanism predominant with β-CD to a cooperative/competitive mixed mechanism operating for the larger derivative. The cavity size in γ-CD is large enough to bind two surfactant alkyl chains with a cooperative effect. Water molecules released by the formation of 1:1 host-guest complexes made the cavity more hydrophobic and promoted further inclusion. A reduction in the available volume of the cavity should be considered on binding a second guest.
authors.affiliation: Departamento de Química Física, Centro de Investigación en Química Biológica y Materiales Moleculares (CIQUS), Universidad de Santiago, 15782 Santiago, Spain. luis.garcia@usc.es.
authors.forename: J
authors.initials: J
authors.lastname: Fernández-Rosas
authors.forename: M
authors.initials: M
authors.lastname: Pessêgo
authors.forename: M
authors.initials: M
authors.lastname: Cepeda-Plaza
authors.forename: N
authors.initials: N
authors.lastname: Basilio
authors.forename: M
authors.initials: M
authors.lastname: Parajó
authors.forename: P
authors.initials: P
authors.lastname: Rodríguez-Dafonte
authors.forename: L
authors.initials: L
authors.lastname: García-Río