Anion recognition by halogen bonding and hydrogen bonding bis(triazole)-imidazolium [2]rotaxanes

Abstract

A novel halogen bonding (XB) bis(iodotriazole)-imidazolium motif is incorporated into the axle component of a [2]rotaxane via a discrete chloride anion template directed clipping methodology. ¹H NMR anion titration experiments reveal the interlocked host is capable of strong halide and sulfate oxoanion binding in competitive aqueous–organic CDCl₃/CD₃OD/D₂O (45 : 45 : 10 v/v) solvent mixtures. In comparison to a hydrogen bonding rotaxane analogue, which exhibited no pronounced selectivity between Cl⁻, I⁻ and SO₄²⁻, the axle iodo-triazole donor motifs of the XB rotaxane modulate the anion recognition preference towards the lighter halides Cl⁻ ≈ Br⁻ > SO₄²⁻ > I⁻.