Contributions of electrostatic and hydrophobic interactions to the host–guest complexation of pyrocatecholate anions with cationic cyclodextrins

Abstract

Binding constants of a series of 4-substituted pyrocatechols (1,2-dihydroxybenzenes) to four 6-deoxy, 6-amino derivatives of β-cyclodextrin have been determined from the kinetics of their auto-oxidation at pH 10.0. In several cases, the binding constants at pH 6.0 have been determined by spectrophotometry. Cationic forms of amino derivatives of β-cyclodextrin bind pyrocatecholate anions with equilibrium constants up to 10⁵ dm³ mol^–1. The electrostatic and hydrophobic interactions were shown to contribute additively to the free energy of the host–guest complexation.