Integrative, Orientational Self-Sorting at the Four-Crossing Level in Molecular Knots and Links

Area of Science:

• Supramolecular Chemistry
• Organic Synthesis
• Materials Science

Background:

• Synthesizing low-symmetry mechanically interlocked molecules (MIMs) is challenging due to their complex structures.
• Existing methods often lack control over the precise assembly of anisotropic MIMs.

Purpose of the Study:

• To develop a self-sorting strategy for the controlled synthesis of diverse low-symmetry MIM topologies.
• To investigate the transformation between different MIM structures using a "MIM-to-MIM" approach.

Main Methods:

• Employed two unsymmetric flexible bidentate ligands (Lab and Lcd) for self-sorting.
• Co-assembled ligands with size-differentiated rigid chelating building blocks and organometallic units.
• Utilized a "MIM-to-MIM" strategy for interconverting molecular architectures.

Main Results:

• Successfully synthesized three discrete MIM topologies: Solomon link (4_1^2), figure-eight knot (4_1), and trefoil knot (3_1).
• Achieved high orientational fidelity in the self-assembly process.
• Demonstrated the first "MIM-to-MIM" transformation between fully interlocked molecular species.
• Constructed a heteroleptic Solomon link in a non-statistical manner via molecular fusion or integrative self-sorting.

Conclusions:

• The developed self-sorting strategy enables precise control over the synthesis of complex MIMs.
• Noncovalent interactions, ligand flexibility, and geometric complementarity are key drivers of complex self-sorting behavior.
• The "MIM-to-MIM" strategy opens new avenues for dynamic manipulation of interlocked molecular architectures.