Herein we report the formation and characterization of a novel type of capsules resulting from the self-association between oppositely charged complementary building blocks in MeOH/H2O. The assembly is based on the interaction between tetraamidinium calixarenes 1a-d and tetrasulfonato calixarene 2. Evidence for the formation of the expected 1:1 assemblies is provided by proton NMR, ESI-MS, and ITC. The association process is fast on the NMR time scale and strongly entropy driven, with association constants in the range of 106 M-1. The system 1a·2 shows binding affinity toward acetylcholine, tetramethylammonium, and N-methylquinuclidinium cations.
Corbellini, F., Fiammengo, R., Timmerman, P., Crego Calama, M., Versluis, K., Heck, A. J. R., ... Reinhoudt, D. (2002). Guest encapsulation and self-assembly of molecular capsules in polar solvents via multiple ionic interactions. Journal of the American Chemical Society, 124(23), 6569-6575. https://doi.org/10.1021/ja012058z