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

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Coordination Chemistry

Background:

• Interlocked molecules, such as catenanes, possess unique properties due to their complex spatial structures.
• Synthesizing and studying the host-guest properties of these molecules present significant challenges.
• Cluster-organic cages offer a promising platform for developing novel supramolecular architectures.

Purpose of the Study:

• To report the formation of a novel [2]catenane through self-assembly.
• To investigate the host-guest properties of the newly synthesized catenane.
• To understand the factors governing the size-specific recognition of cations within the catenane structure.

Main Methods:

• Self-assembly of a cluster node ([Tp*WS3Cu3Cl]+) and an organic linker (cis-bpype).
• Single-crystal X-ray diffraction and Nuclear Magnetic Resonance (NMR) spectroscopy for structural characterization.
• Cation encapsulation experiments and theoretical calculations (volume analysis) to probe host-guest interactions.

Main Results:

• Successful synthesis of a novel [2]catenane, [Et4N]@[ (Tp*WS3Cu3Cl)2(cis-bpype)3 ]2(OTf)5, via self-assembly.
• Structural elucidation revealed the catenane is formed by the interpenetration of two cluster-organic cages.
• The catenane demonstrated adaptive encapsulation of specific cations ([Et4N]+, [Pr4N]+) but excluded others ([Bu4N]+, [Me4N]+), indicating size-specific recognition.
• Host-guest complexation was influenced by electrostatic repulsion and noncovalent interactions.

Conclusions:

• The novel catenane exhibits unique cation-in-cation host-guest complexation behavior.
• The formation of the empty catenane was facilitated by electrostatic repulsion.
• The catenane's structure and the interplay of electrostatic and noncovalent forces enable size-specific cation recognition, offering insights into molecular recognition mechanisms.