A trefoil knot self-templated through imination in water

The self-assembly of molecular knots in water is challenging. Here, authors report the self-assembly of a trefoil knot in water via imine condensation, without relying on external templates; the handedness of the trefoil knot is determined by the chirality of the bisamino precursor. The preparation of topologically nontrivial molecules is often assisted by covalent, supramolecular or coordinative templates that provide spatial pre-organization for all components. Herein, we report a trefoil knot that can be self-assembled efficiently in water without involving additional templates. The direct condensation of three equivalents of a tetraformyl precursor and six equivalents of a chiral diamine produces successfully a [3 + 6] trefoil knot whose intrinsic handedness is dictated by the stereochemical configuration of the diamine linkers. Contrary to the conventional wisdom that imine condensation is not amenable to use in water, the multivalent cooperativity between all the imine bonds within the framework makes this trefoil knot robust in the aqueous environment. Furthermore, the presence of water is proven to be essential for the trefoil knot formation. A topologically trivial macrocycle composed of two tetraformyl and four diamino building blocks is obtained when a similar reaction is performed in organic media, indicating that hydrophobic effect is a major driving force behind the scene.

Automated summary

This study reports a new method to self-assemble a trefoil knot in water via imine condensation, without the need for external templates. The handedness of the knot is determined by the chirality of the precursor molecules, and the presence of water is essential for its formation. The hydrophobic effect plays a key role in driving the reaction.