Abstract
Double helical conformation of polymer chains is widely observed in biomacromolecules and plays an essential role in exerting their biological functions, such as molecular recognition and information storage. It has remained challenging, however, to prepare synthetic helical polymers, and those that exist have mainly been limited to single-stranded polymers or short oligomeric double helices. Here, we report the synthesis of covalent helical polymers, with a high molecular weight, from the achiral monomer hexahydroxytriphenylene through to spiroborate formation. Polymerization and crystallization occurred simultaneously under solvothermal conditions to form single crystals of the resulting helical covalent polymers. Characterization by single-crystal X-ray diffraction showed that each crystal consisted of pairs of mechanically entwined polymers. No strong non-covalent interactions were observed between the two helical polymers that formed a pair; instead, each strand interacted with neighbouring pairs through hydrogen bonding. Each individual crystal was made up of helical polymers of the same handedness, but the crystallization process produced a racemic conglomerate, with equal amounts of right-handed and left-handed crystals.
Similar content being viewed by others
Data availability
Experimental data and characterization data are provided in the Supplementary Information. Crystallographic data for the two crystals of 1 (tentatively assigned to right-handed) reported in this Article have been deposited at the Cambridge Crystallographic Data Centre, under deposition numbers CCDC 2017159 (HCP crystal 1) and 2034057 (HCP crystal 2). Copies of the data can be obtained free of charge via https://www.ccdc.cam.ac.uk/structures/.
References
Watson, J. D. & Crick, F. H. C. Molecular structure of nucleic acids: a structure for deoxyribose nucleic acid. Nature 171, 737–738 (1953).
Yashima, E. et al. Supramolecular helical systems: helical assemblies of small molecules, foldamers, and polymers with chiral amplification and their functions. Chem. Rev. 116, 13752–13990 (2016).
Hill, D. J., Mio, M. J., Prince, R. B., Hughes, T. S. & Moore, J. S. A field guide to foldamers. Chem. Rev. 101, 3893–4012 (2001).
Zhang, D.-W., Zhao, X., Hou, J.-L. & Li, Z.-T. Aromatic amide foldamers: structures, properties, and functions. Chem. Rev. 112, 5271–5316 (2012).
Nakano, T. & Okamoto, Y. Synthetic helical polymers: conformation and function. Chem. Rev. 101, 4013–4038 (2001).
Yashima, E., Maeda, K., Iida, H., Furusho, Y. & Nagai, K. Helical polymers: synthesis, structures, and functions. Chem. Rev. 109, 6102–6211 (2009).
Percec, V. et al. Steric communication of chiral information observed in dendronized polyacetylenes. J. Am. Chem. Soc. 128, 16365–16372 (2006).
Percec, V. et al. Self‐assembling phenylpropyl ether dendronized helical polyphenylacetylenes. Chem. Eur. J. 13, 9572–9581 (2007).
Percec, V. et al. Synthesis, structural, and retrostructural analysis of helical dendronized poly(1‐naphthylacetylene)s. J. Polym. Sci. A 45, 4974–4987 (2007).
Rudick, J. G. & Percec, V. Nanomechanical function made possible by suppressing structural transformations of polyarylacetylenes. Macromol. Chem. Phys. 209, 1759–1768 (2008).
Motoshige, A., Mawatari, Y., Motoshige, R., Yoshida, Y. & Tabata, M. Contracted helix to stretched helix rearrangement of an aromatic polyacetylene prepared in n‐hexane with [Rh(norbornadiene)Cl]2‐triethylamine catalyst. J. Polym. Sci. A 51, 5177–5183 (2013).
Liu, X.-Q., Wang, J., Yang, S. & Chen, E.-Q. Self-organized columnar phase of side-chain liquid crystalline polymers: to precisely control the number of chains bundled in a supramolecular column. ACS Macro Lett. 3, 834–838 (2014).
Lehn, J.-M. et al. Spontaneous assembly of double-stranded helicates from oligobipyridine ligands and copper (i) cations: structure of an inorganic double helix. Proc. Natl Acad. Sci. USA 84, 2565–2569 (1987).
Berl, V., Huc, I., Khoury, R. G., Krische, M. J. & Lehn, J.-M. Interconversion of single and double helices formed from synthetic molecular strands. Nature 407, 720–723 (2000).
Miwa, K., Furusho, Y. & Yashima, E. Ion-triggered spring-like motion of a double helicate accompanied by anisotropic twisting. Nat. Chem. 2, 444–449 (2010).
Ousaka, N. et al. Spiroborate-based double-stranded helicates: meso-to-racemo isomerization and ion-triggered springlike motion of the racemo-helicate. J. Am. Chem. Soc. 140, 17027–17039 (2018).
Wang, Y. et al. Double helical conformation and extreme rigidity in a rodlike polyelectrolyte. Nat. Commun. 10, 801 (2019).
Kusanagi, H., Chatani, Y. & Tadokoro, H. The crystal structure of isotactic poly(methyl methacrylate): packing-mode of double stranded helices. Polymer 35, 2028–2039 (1994).
Liu, Y. et al. Weaving of organic threads into a crystalline covalent organic framework. Science 351, 365–369 (2016).
Leiras, S., Freire, F., Quiñoá, E. & Riguera, R. Reversible assembly of enantiomeric helical polymers: from fibers to gels. Chem. Sci. 6, 246–253 (2015).
Beaudoin, D., Maris, T. & Wuest, J. D. Constructing monocrystalline covalent organic networks by polymerization. Nat. Chem. 5, 830–834 (2013).
Evans, A. M. et al. Seeded growth of single-crystal two-dimensional covalent organic frameworks. Science 361, 52–57 (2018).
Ma, T. et al. Single-crystal X-ray diffraction structures of covalent organic frameworks. Science 361, 48–52 (2018).
Acknowledgements
We thank V. Ferguson and A. Tomaschke for the nano-indentation tests, D. Gin for the assistance with the PXRD facility, B. Lama for the solid-state NMR measurements and X. Tang for circular dichroism measurements. We thank the University of Colorado Boulder for funding support. Y.C. acknowledges support from the National Science Foundation of China (91856204) and Key Project of Basic Research of Shanghai (18JC1413200). W.G. is supported by the China Postdoctoral Science Foundation (2019M661482). Z.Z. and T.J. are sponsored by the Shanghai Pujiang Talent Plan (no. 20PJ1414100) and the National Natural Science Foundation of China (62005198). X.C. is supported by the National Natural Science Foundation of China (no. 61925504). This research used resources of the Advanced Light Source, which is a DOE Office of Science User Facility, under contract no. DE-AC02-05CH11231.
Author information
Authors and Affiliations
Contributions
Y.H., Y.J. and W.Z. conceived the idea and led the project. Y.H., H.C. and J.W. conducted the synthesis and crystal growth. W.G., Y.C. and S.J.T. carried out single-crystal study and structure refinement. Z.Z., T.J. and X.C. performed the AFM test and infrared scattering scanning nearfield optical microscopy measurements. Y.J. and W.Z. wrote the manuscript with help from Y.H. and Y.C. All authors discussed and revised the manuscript.
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing interests.
Additional information
Peer review information Nature Chemistry thanks the anonymous reviewers for their contribution to the peer review of this work.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary information
Supplementary Information
Supplementary Figs. 1–13, Discussion and Tables 1–5.
Supplementary Data 1
Crystallographic data of the helical covalent polymer, crystal 1; CCDC 2017159.
Supplementary Data 2
Crystallographic data of the helical covalent polymer, crystal 2; CCDC 2034057.
Supplementary Data 3
Source data for Supplementary Fig. 7.
Rights and permissions
About this article
Cite this article
Hu, Y., Teat, S.J., Gong, W. et al. Single crystals of mechanically entwined helical covalent polymers. Nat. Chem. 13, 660–665 (2021). https://doi.org/10.1038/s41557-021-00686-2
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/s41557-021-00686-2
- Springer Nature Limited
This article is cited by
-
Linkage conversions in single-crystalline covalent organic frameworks
Nature Chemistry (2024)
-
Encoding ordered structural complexity to covalent organic frameworks
Nature Communications (2024)
-
Self-similar chiral organic molecular cages
Nature Communications (2024)
-
A spirocyclic backbone accesses new conformational space in an extended, dipole-stabilized foldamer
Communications Chemistry (2023)
-
Reconstructed covalent organic frameworks
Nature (2022)