During the past decades, the development of efficient methodologies for the creation of mechanically interlocked molecules (MIMs), such as catenanes and rotaxanes, has, not only laid the foundation for the design and syntheses of artificial molecular machines (AMMs), but also opened up new research opportunities in multiple disciplines, ranging from contemporary chemistry to materials science. Among all types of MIMs, three-dimensional (3D) catenanes, which are composed of multiple cage-shaped components, are a subset that are far from easy to make. Previously, the formation of 3D catenanes has mainly relied on self-assembly, in which the reversible formation of dynamic bonds acts as an error-checking mechanism to ensure the generation of 3D catenanes under thermodynamic control. In this study, we demonstrate that thermodynamically disfavored 3D catenanes can be constructed under kinetic control. The syntheses take advantage of a sequence of irreversible S<sub>N</sub>2 reactions in one pot, generating a pair of 3D catenanes which do not represent thermodynamic minima. Mechanistic studies have revealed that a suit[3]ane, which contains a 3-fold symmetric cage component as the suit and a tribromide component as the body, is formed at elevated temperatures. This suit[3]ane was identified as the key reactive intermediate for the selective formation of the two 3D catenanes under kinetic control. Together with synthetic methodologies based on metal coordination and dynamic covalent chemistry, this particular synthetic approach brings us one step closer to realizing routine syntheses of 3D catenanes.

Syntheses of three-dimensional catenanes under kinetic control

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