Interlocked molecular architectures, such as rotaxanes and catenanes, are of great interest because of their proposed utilization in molecular machines and nanotechnological applications. Despite the usefulness of emissive lanthanide complexes in imaging, sensing, and assay, the integration of lanthanide reporter groups within the binding cavity of interlocked hosts has not been achieved.

Stephen Faulkner, Paul D. Beer, and colleagues, University of Oxford, UK, describe the first anion-templated synthesis of a lanthanide-containing interlocked molecule, by the unprecedented use of a nitrite anion template. The bidentate coordination behaviour of a nitrite anion is used to template the formation of a pseudorotaxane assembly, by simultaneous coordination to a lanthanide cation incorporated within a macrocycle and a hydrogen-bond donor threading component.

The [2]rotaxane host system, isolated in high yields, is capable of sensing fluoride anions selectively by means of the luminescent europium center integrated within the rotaxanes macrocycle component.

• Nitrite-Templated Synthesis of Lanthanide-Containing [2]Rotaxanes for Anion Sensing,
  Matthew J. Langton, Octavia A. Blackburn, Thomas Lang, Stephen Faulkner, Paul D. Beer,
  Angew. Chem. Int. Ed. 2014.
  DOI: 10.1002/anie.201405131