Self-Assembly of Cluster-Mediated 3D Catenanes with Size-Specific Recognition Behavior

Although interlocked three-dimensional molecules display unique properties associated with their spatial structures, their synthesis and study of their host-guest properties remain challenging. We report the formation of a novel [2]catenane, [Et₄N]@[(Tp*WS₃Cu₃Cl)₂(cis-bpype)₃]₂(OTf)₅ ([Et₄N][1](OTf)₅), by self-assembly of the cluster node [Tp*WS₃Cu₃Cl]⁺ and the organic linker (Z)-1,2-diphenyl-1,2-bis(4-(pyridin-4-yl)phenyl)ethene (cis-bpype). Single-crystal X-ray and NMR analyses established that [1]⁴⁺ is formed by the interpenetration of two cluster-organic cages. Unique cation-in-cation host-guest complexes were observed with this catenane. The crystalline, empty catenane was formed by taking advantage of the electrostatic repulsion-induced weak binding of the host. Encapsulation experiments also reveal that the empty catenane can adaptively encapsulate cations such as [Et₄N]⁺ and [Pr₄N]⁺ in the cross cavity but is unable to encapsulate [Bu₄N]⁺ and [Me₄N]⁺, although the size of the latter is compatible with that of the cavity. Theoretical calculations and volume analysis allow to unravel the ingenious role of catenane structures and the interplay between electrostatic repulsion and attractive noncovalent interactions for size-specific recognition behavior in host-guest systems involving species with similar electric charges.