Unexpected solvent effect on the binding of positively-charged macrocycles to neutral aromatic hydrocarbons

Abstract

Two positively-charged naphthotubes with imidazolium as the bridges were synthesized and their structures have been characterized by ¹H NMR, MS, and X-ray crystallography. These naphthotubes are capable of binding aromatic hydrocarbons. Surprisingly, the binding affinities are much higher in CD₃CN than in CD₂Cl₂. The solvent effect on the ion pairing interactions and competitive binding of CD₂Cl₂ was invoked to explain this unusual phenomenon.