Self-assembled poly-catenanes from supramolecular toroidal building blocks

Datta, Sougata and Kato, Yasuki and Higashiharaguchi, Seiya and Aratsu, Keisuke and Isobe, Atsushi and Saito, Takuho and Prabhu, Deepak D. and Kitamoto, Yuichi and Hollamby, Martin J. and Smith, Andrew J. and Dalgliesh, Robert and Mahmoudi, Najet and Pesce, Luca and Perego, Claudio and Pavan, Giovanni M. and Yagai, Shiki (2020) Self-assembled poly-catenanes from supramolecular toroidal building blocks. Nature, 583 (7816). pp. 400-405. ISSN 0028-0836

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Mechanical interlocking of molecules (catenation) is a nontrivial challenge in modern synthetic chemistry and materials science[1,2]. One strategy to achieve catenation is the design of pre-annular molecules that are capable of both efficient cyclization and of pre-organizing another precursor to engage in subsequent interlocking[3-9]. This task is particularly difficult when the annular target is composed of a large ensemble of molecules, that is, when it is a supramolecular assembly. However, the construction of such unprecedented assemblies would enable the visualization of nontrivial nanotopologies through microscopy techniques, which would not only satisfy academic curiosity but also pave the way to the development of materials with nanotopology-derived properties. Here we report the synthesis of such a nanotopology using fibrous supramolecular assemblies with intrinsic curvature. Using a solvent-mixing strategy, we kinetically organized a molecule that can elongate into toroids with a radius of about 13 nanometres. Atomic force microscopy on the resulting nanoscale toroids revealed a high percentage of catenation, which is sufficient to yield ‘nanolympiadane’[10], a nanoscale catenane composed of five interlocked toroids. Spectroscopic and theoretical studies suggested that this unusually high degree of catenation stems from the secondary nucleation of the precursor molecules around the toroids. By modifying the self-assembly protocol to promote ring closure and secondary nucleation, a maximum catenation number of 22 was confirmed by atomic force microscopy. [1] Segawa, Y. et al. Topological molecular nanocarbons: all-benzene catenane and trefoil knot. Science 365, 272–276 (2019). [2] Leigh, D. A., Pritchard, R. G. & Stephens, A. J. A Star of David catenane. Nat. Chem. 6, 978–982 (2014). [3] Li, H. et al. Quantitative self-assembly of a purely organic three-dimensional catenane in water. Nat. Chem. 7, 1003–1008 (2015). [4] Fujita, M., Ibukuro, F., Hagihara, H. & Ogura, K. Quantitative self-assembly of a [2]catenane from two preformed molecular rings. Nature 367, 720–723 (1994). [5] Hunter, C. A. Synthesis and structure elucidation of a new [2]-catenane. J. Am. Chem. Soc. 114, 5303–5311 (1992). CAS Article Google Scholar [6] Ashton, P. R. et al. A [2]catenane made to order. Angew. Chem. Int. Ed. 28, 1396–1399 (1989). [7] Dietrich-Buchecker, C. O., Sauvage, J. P. & Kintzinger, J. P. Une nouvelle famille de molecules: les metallo-catenanes. Tetrahedr. Lett. 24, 5095–5098 (1983). [8] Wasserman, E. Chemical topology. Sci. Am. 207, 94–102 (1962). [9] Wu, Q. et al. Poly[n]catenanes: synthesis of molecular interlocked chains. Science 358, 1434–1439 (2017). [10] Amabilino, D. B., Ashton, P. R., Reder, A. S., Spencer, N. & Stoddart, J. F. Olympiadane. Angew. Chem. Int. Ed. 33, 1286–1290 (1994).

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