Copper(II)-directed synthesis of neutral heteroditopic [2]rotaxane ion-pair host systems incorporating hydrogen and halogen bonding anion binding cavities

Neutral heteroditopic [2]rotaxane ion-pair host systems were synthesised via a Cu(II) directed passive metal template strategy. Each rotaxane contains discrete, axle-separated interlocked binding sites for a guest anion and a transition metal countercation. The anion binding sites are composed of convergent X–H (X = C, N) hydrogen bond donor groups, or mixed X–H and C–I hydrogen and halogen bond donor groups, whereas an equivalent three-dimensional array of amine, pyridine and carbonyl oxygen donor groups comprise the transition metal binding site. ¹H NMR titrations experiments in CDCl₃/CD₃OD or CDCl₃/CD₃OD/D₂O solvent mixtures reveal that the heteroditopic [2]rotaxane host systems are capable of cooperative anion recognition in the presence of a co-bound Zn(II) cation.