Braiding a molecular knot with eight crossings

Area of Science:

• Supramolecular Chemistry
• Nanotechnology
• Chemical Synthesis

Background:

• Molecular knots offer potential for nanoscale applications, but their synthesis is limited to simple structures.
• Investigating the impact of molecular knotting requires accessible synthetic routes to complex knots.

Purpose of the Study:

• To develop a general synthetic strategy for complex molecular knots.
• To enable systematic studies on the relationship between molecular topology and properties.

Main Methods:

• Assembly of four building blocks into three braided ligand strands.
• Utilizing octahedral iron(II) ions to direct strand positioning in a circular triple helicate.
• Employing ligand structural constraints to define braiding connections.

Main Results:

• Successful two-step synthesis of a molecular 819 knot.
• The knot is a 192-atom closed loop approximately 20 nanometers in length.
• Resolved metal-free 819 knot enantiomers exhibit distinct circular dichroism spectra due to topological chirality.

Conclusions:

• The developed method provides a viable route to complex molecular knots.
• This facilitates the exploration of topological chirality and its effects at the molecular level.
• Nanoscale molecular knots can be designed and synthesized for advanced applications.