Anion-Templated Assembly of Pseudorotaxanes: Importance of Anion Template, Strength of Ion-Pair Thread Association, and Macrocycle Ring Size

A wide range of pseudorotaxane assemblies containing positively charged pyridinium, pyridinium
nicotinamide, imidazolium, benzimidazolium and guanidinium threading components, and macrocyclic
isophthalamide polyether ligands have been prepared using a general anion templation procedure. In
noncompetitive solvent media, coupling halide anion recognition by a macrocyclic ligand with ion-pairing
between the halide anion and a strongly associated cation provides the driving force for interpenetration.
Extensive solution 1H NMR binding studies, thermodynamic investigations, and single-crystal X-ray structure
determinations reveal that the nature of the halide anion template, strength of the ion-pairing between the
anion template and the cationic threading component, and to a lesser extent favorable second sphere
π−π aromatic stacking interactions between the positively charged threading component and macrocyclic
ligand, together with macrocyclic ring size, affect the efficacy of pseudorotaxane formation.