Quantitative self-assembly of a [2]catenane from two preformed molecular rings

MOLECULES composed of interlocking rings are termed catenanes. Since the first synthesis of a two-ring catenane (a [2]catenane) in 19601, these and related interlinked compounds have attracted considerable interest2–10, in part from the perspective of forming molecular devices and nanoscale architectures11,12. Here we report the formation of a [2]catenane from two complete rings, reminiscent of the trick of interlinking 'magic rings'. This supermolecule, 1 in Fig. 1, exists in rapid equilibrium with the monomeric rings 2, as revealed by 1H NMR and electrospray mass spectrometry. At low concentration of molecule 2, the equilibrium lies towards the monomers, but at higher concentrations the catenane is the overwhelmingly dominant species in solution.