Discovery of an Organic Trefoil Knot

1. Nandhini Ponnuswamy¹, 
2. Fabien B. L. Cougnon¹, 
3. Jessica M. Clough¹, 
4. G. Dan Pantoş², 
5. Jeremy K. M. Sanders¹,*

Science 9 November 2012: 
Vol. 338 no. 6108 pp. 783-785 
DOI: 10.1126/science.1227032

ABSTRACT

Molecular knots remain difficult to produce using the current synthetic methods of chemistry because of their topological complexity. We report here the near-quantitative self-assembly of a trefoil knot from a naphthalenediimide-based aqueous disulfide dynamic combinatorial library. The formation of the knot appears to be driven by the hydrophobic effect and leads to a structure in which the aromatic components are buried while the hydrophilic carboxylate groups remain exposed to the solvent. Moreover, the building block chirality constrains the topological conformation of the knot and results in its stereoselective synthesis. This work demonstrates that the hydrophobic effect provides a powerful strategy to direct the synthesis of entwined architectures.