A synthetic molecular pentafoil knot

Abstract

Knots are being discovered with increasing frequency in both biological and synthetic macromolecules and have been fundamental topological targets for chemical synthesis for the past two decades. Here, we report on the synthesis of the most complex non-DNA molecular knot prepared to date: the self-assembly of five bis-aldehyde and five bis-amine building blocks about five metal cations and one chloride anion to form a 160-atom-loop molecular pentafoil knot (five crossing points). The structure and topology of the knot is established by NMR spectroscopy, mass spectrometry and X-ray crystallography, revealing a symmetrical closed-loop double helicate with the chloride anion held at the centre of the pentafoil knot by ten CH···Cl– hydrogen bonds. The one-pot self-assembly reaction features an exceptional number of different design elements—some well precedented and others less well known within the context of directing the formation of (supra)molecular species. We anticipate that the strategies and tactics used here can be applied to the rational synthesis of other higher-order interlocked molecular architectures. The most complex non-DNA molecular knot prepared so far is self-assembled around a chloride anion from five metal cations, five bis-aldehyde and five bis-amine building blocks, in a one-pot reaction. The X-ray crystal structure of the 160-atom-loop pentafoil knot reveals a symmetrical closed-loop double helicate with a chloride anion held at its centre by ten CH···Cl− hydrogen bonds.

Cite this article

Ayme, JF., Beves, J., Leigh, D. et al. A synthetic molecular pentafoil knot. Nature Chem 4, 15–20 (2012). https://doi.org/10.1038/nchem.1193

View full text

>> Full Text:   A synthetic molecular pentafoil knot