An infinite chainmail of M6L6 metallacycles featuring multiple Borromean links


Borromean rings or links are topologically complex assemblies of three entangled rings where no two rings are interlinked in a chain-like catenane, yet the three rings cannot be separated. We report here a metallacycle complex whose crystalline network forms the first example of a new class of entanglement. The complex is formed from the self-assembly of CuBr2 with the cyclotriveratrylene-scaffold ligand (±)-tris(iso-nicotinoyl)cyclotriguaiacylene. Individual metallacycles are interwoven into a two-dimensional chainmail network where each metallacycle exhibits multiple Borromean-ring-like associations with its neighbours. This only occurs in the solid state, and also represents the first example of a crystalline infinite chainmail two-dimensional network. Crystals of the complex were twinned and have an unusual hollow tubular morphology that is likely to result from a localized dissolution-recrystallization process.

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Figure 1: Examples of entangled ring assemblies.
Figure 2: Metallacycles and Borromean-ring motifs from the crystal structure of complex 1.
Figure 3: Extended Borromean-ring motifs in complex 1.
Figure 4: Details from the crystal structure of complex 1, highlighting interactions between chainmail layers.
Figure 5: FEG-SEM images of crystals of complex 1.


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The authors acknowledge the Engineering and Physical Sciences Research Council for funding this research, T. Marinko-Covell for microanalysis, A. Kazlauciunas for EDX and thermal gravimetric analysis measurements and S. Warriner for assistance with mass spectrometry. The authors thank S. Hyde for useful discussions regarding topology. The authors acknowledge Diamond Light Source for time on beamline I19 under proposal MT8911.

Author information

F.L.T-G. and M.J.H. conceived and designed experiments. F.L.T-G. performed synthetic, crystallographic and other characterization experiments and A.N.K. performed SEM experiments. All authors contributed to analysis of the data. M.J.H. wrote the paper with discussions and contributions from F.L.T-G. and some diagrams prepared by A.N.K.

Correspondence to Michaele J. Hardie.

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Thorp-Greenwood, F., Kulak, A. & Hardie, M. An infinite chainmail of M6L6 metallacycles featuring multiple Borromean links. Nature Chem 7, 526–531 (2015) doi:10.1038/nchem.2259

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