Tetracationic Zn(II) porphyrinates and tetraanionic calixarenes can be assembled in polar solvents to obtain cage-like complexes in an entropy driven process. These structures are remarkably stable even in the presence of water or competing salts.
Fiammengo, R., Timmerman, P., de Jong, F., & Reinhoudt, D. (2000). Highly stable cage-like complexes by self-assembly of tetracationic Zn(II) porphyrinates and tetrasulfonatocalixarenes in polar solvents. Chemical communications, 2000(23), 2313-2314. https://doi.org/10.1039/b006960o