Orthogonal cation and anion template-directed synthesis of a heteroditopic [3]catenane for ion-pair recognition

The first orthogonal template strategy for the synthesis of higher order interlocked structures is described. Orthogonal cation and anion templates were employed in a stepwise fashion to construct a hetero[3]catenane composed of structurally distinct macrocyclic components. Importantly, the [3]catenane contains two interlocked binding cavities tailored for cation and anion binding, enabling it to function as a heteroditopic ion-pair receptor. The co-conformational dynamics and cation/anion binding properties of the [3]catenane were investigated by ¹H NMR studies, which displayed temperature-dependent and guest-induced changes in chemical shift and linewidth. The potent ion-pair binding capability of the [3]catenane was confirmed by single-crystal X-ray diffraction studies, which showed the [3]catenane to recognise a sodium chloride ion-pair in a mechanically bonded receptor-separated ion-pair binding mode, wherein the two guest ions are encapsulated within their respective interlocked host cavities.