An “All-in-One” Synthetic Strategy for Linear Metalla4Catenanes

One fascinating and challenging synthetic target in the field of mechanically interlocked molecules is the family of linear 4catenanes, which are topologically identical to the logo of automobile maker Audi. Herein, we report an “all-in-one” synthetic strategy for the synthesis of linear metallancatenanes (n = 2–4) by the coordination-driven self-assembly of Cp*Rh-based (Cp* = η5-pentamethylcyclopentadienyl) organometallic rectangle π-donors and tetracationic organic cyclophane π-acceptors. We selected the pyrenyl group as the π-donor unit, leading to homogeneous metalla2catenanes and cyclic metalla3catenanes via π-stacking interactions. By taking advantage of the strong electrostatic interactions between π-donor units and π-acceptor units, a heterogeneous metalla2catenanes and linear metalla3catenanes, respectively, could be obtained by the simple stirring of homogeneous metalla2catenanes with a suitable tetracationic cyclophane. On this basis, this “all-in-one” synthetic strategy was further used to realize a quantitative one-step synthesis of a linear metalla4catenanes via the self-assembly of cyclic metalla3catenanes and tetracationic cyclophanes. All heterogeneous metallancatenanes (n = 2–4) were fully characterized by single-crystal X-ray analysis, NMR spectroscopy and electrospray ionization mass spectrometry.