High aspect ratio nanotubes assembled from macrocyclic iminium salts

Chao Sun, Meng Shen, Anton D. Chavez, Austin M. Evans, Xiaolong Liu, Boris Harutyunyan, Nathan C. Flanders, Mark C. Hersam, Michael J. Bedzyk, Monica Olvera de la Cruz*, William R. Dichtel

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


One-dimensional nanostructures such as carbon nanotubes and actin filaments rely on strong and directional interactions to stabilize their high aspect ratio shapes. This requirement has precluded making isolated, long, thin organic nanotubes by stacking molecular macrocycles, as their noncovalent stacking interactions are generally too weak. Here we report high aspect ratio (>10 3 ), lyotropic nanotubes of stacked, macrocyclic, iminium salts, which are formed by protonation of the corresponding imine-linked macrocycles. Iminium ion formation establishes cohesive interactions that, in organic solvent (tetrahydrofuran), are two orders of magnitude stronger than the neutral macrocycles, as explained by physical arguments and demonstrated by molecular dynamics simulations. Nanotube formation stabilizes the iminium ions, which otherwise rapidly hydrolyze, and is reversed and restored upon addition of bases and acids. Acids generated by irradiating a photoacid generator or sonicating chlorinated solvents also induced nanotube assembly, allowing these nanostructures to be coupled to diverse stimuli, and, once assembled, they can be fixed permanently by cross-linking their pendant alkenes. As large macrocyclic chromonic liquid crystals, these iminium salts are easily accessible through a modular design and provide a means to rationally synthesize structures that mimic the morphology and rheology of carbon nanotubes and biological tubules.

Original languageEnglish (US)
Pages (from-to)8883-8888
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number36
StatePublished - Sep 4 2018


  • Macrocycles
  • Molecular dynamics
  • Nanotubes
  • Stimuli-responsive materials
  • Supramolecular chemistry

ASJC Scopus subject areas

  • General


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