Octapi interactions: self-assembly of a Pd-based [2]catenane driven by eightfold pi interactions.

Area of Science:

• Supramolecular Chemistry
• Organic Chemistry
• Materials Science

Background:

• Catenanes are mechanically interlocked molecular architectures with unique properties.
• Pi-pi interactions are crucial non-covalent forces in molecular assembly.
• Controlling the formation of complex interlocked structures remains a challenge.

Purpose of the Study:

• To investigate the role of pi-pi interactions in templating the formation of [2]catenanes.
• To explore the influence of ligand length on catenane synthesis.
• To characterize the stability of the formed catenated complex in solution.

Main Methods:

• Synthesis of metallamacrocycles using aromatic ligands.
• Self-assembly driven by pi-pi interactions.
• Spectroscopic and structural analysis (e.g., NMR, X-ray crystallography) to confirm structure and interlocked state.

Main Results:

• An array of eight aromatic rings and 2.5 nm pi-pi interactions successfully templated the formation of a [2]catenane.
• Using longer ligands disrupted the pi-interaction array, leading to the formation of uncatenated rings.
• The [2]catenane was observed to be stable in solution, coexisting with its precursor metallamacrocycles.

Conclusions:

• Precise control over pi-pi interaction geometry is essential for templating complex interlocked molecules like catenanes.
• Ligand design is a critical factor in directing the self-assembly pathway towards catenation or simple macrocyclization.
• The study demonstrates a method for constructing and stabilizing mechanically interlocked molecules via non-covalent interactions.