A molecular endless (7₄) knot

Area of Science:

• Supramolecular Chemistry
• Chemical Synthesis
• Materials Science

Background:

• Traditional molecular knot synthesis involves complex twisting, folding, or threading of molecular building blocks.
• Developing new strategies for creating complex molecular topologies is crucial for advancing nanotechnology and materials science.

Purpose of the Study:

• To report a novel method for synthesizing molecular knots and interlocked structures using metal-ion-templated weaving.
• To demonstrate the formation of a specific seven-crossing knot topology (7₄) and other complex architectures.

Main Methods:

• Utilizing zinc (II) or iron (II) ions to coordinate ligand strands into a woven 3×3 molecular grid.
• Employing tetrafluoroborate anions as templates to direct the self-assembly of the grid structure.
• Performing in-grid alkene metathesis reactions to join the strand ends and form closed-loop structures.

Main Results:

• Successfully synthesized a woven 3×3 molecular grid templated by tetrafluoroborate anions and metal ions.
• Generated a topologically trivial macrocycle (unknot), a doubly interlocked [2]catenane (Solomon link), and a 7₄ knot through post-assembly reactions.
• The 7₄ knot achieved has a 258-atom-long closed loop and corresponds to the endless knot motif found in cultural art.

Conclusions:

• Anion-templated metal-ion coordination provides a powerful strategy for weaving molecular strands into discrete layers.
• This approach enables the synthesis of diverse molecular knot topologies and opens possibilities for creating woven polymer materials.