The self-assembly of a [2]pseudorotaxane of α-cyclodextrin by the slippage mechanism

Abstract

The kinetics and thermodynamics of the self-assembly of a [2]pseudorotaxane comprised of α-cyclodextrin and the 1,10-bis[1-(4-tert-butylpyridinium)]decane dication, by means of a slippage procedure, have been measured in aqueous solutions using ¹H NMR spectroscopy. The very slow threading of the α-cyclodextrin [k₁=(4.2 ± 0.3)× 10^–4 s^–1 at 25 °C] is preceded by a weak inclusion of the tert-butylpyridinium end group (K_CD= 18 ± 3 dm³ mol^–1). The dissociation of the [2]pseudorotaxane occurs with a rate constant of (4.2 ± 0.2)× 10^–6 s^–1 at 25 °C, yielding a pseudorotaxane stability constant of (1.8 ± 0.2)× 10³ dm³ mol^–1.