Synthesis of linear [7]- and [8]catenanes

Catenanes are a family of mechanically interlocked molecules that consist of molecular rings that can be interlocked to give linear, radial, or cyclic structures. Although chemists have pursued extended linear poly[n]catenane architectures for many decades, there still exists a fundamental gap between the synthesis of well-defined, linear oligomers and that of disperse polymers that are often produced as a mixture of architectures. Here, we report two convergent one-pot syntheses that “zip-tie” together two pre-made [3]catenanes by first using orthogonal metal templation with phenanthroline (Cu(I)) and terpyridine (Fe(II)) ligands. These pre-catenate complexes were subjected to a ring-closing metathesis step to afford discrete, linear [7]- and [8]catenanes. The successful synthesis and isolation of the discrete [7]- and [8]catenanes were confirmed using multiple methods of characterization. Because these record-setting linear [n]catenanes possess open phenanthroline metal-binding sites at each end, further expansion to all-interlocked linear poly[n]catenanes is a realistic proposition.