Self-Assembly Synthesis of a [2]Catenane Co^II Single-Molecule Magnet

We describe herein the self-assembly synthesis of an octanuclear Co^II [2]catenane {[Co₄ (H₂ L)₆ ]₂ ¹⁶⁺ } formed by the mechanical interlocking of two {[Co₄ (H₂ L)₆ ]⁸⁺ } rectangles of unprecedented topology. Subtle manipulation of the synthetic conditions allows the isolation of a mixed-valence [Co₂ ^III /Co₂ ^II ]¹⁰⁺ non-catenated rectangle. The Co^II centers in the [2]catenane exhibit slow relaxation of their magnetic moment, i. e. single-molecule magnet properties, dominated by quantum tunneling and Raman relaxation processes. This work shows that metallo-supramolecular chemistry can precisely control the organization of single-molecule magnets in topologically complex arrangements.