Amphiphilic Organic Cages: Self-Assembly into Nanotubes and Enhanced Anion-π Interactions

An amphiphilic organic cage was synthesized and used as self-assembly synthon for the fabrication of novel functional supramolecular structures in solution. The transmission electron microscopy (TEM) results showed that this amphiphilic cage self-assembled in aqueous solution into unilamellar nanotubes with a diameter of 29±4 nm at a concentration of 0.05 mg mL^-1 . Interestingly, the self-assembly of this cage significantly enhanced the anion-π interactions as indicated by a remarkable increasement of association constant (K_a ) between Cl^- and this amphiphilic cage after self-assembly. In specific, K_a was increased from 223 M^-1 for discrete cages in methanol to 6800 M^-1 for aggregated cages after self-assembly in water at the same concentration of 2.26×10^-5  M. A mechanism based on a synergistic effect was proposed in order to explain this self-assembly process through enhanced anion-π interactions.