Metal-dependent selective formation of calix[4]arene assemblies based on dynamic covalent chemistry.

The reaction of calix[4]arene derivatives 1a and 1b bearing four salicylaldehyde moieties with 1,3-propanediamine gave macrocyclic trimers 5a and 5b, respectively, which have intramolecular bridges formed via the flattened cone conformation. In contrast, a capsular-shaped dimeric cage [7a·2Na]2+ was selectively formed when the conformation of the calix[4]arene moiety of 1a was fixed in the spread cone conformation by complexation with Na+ at the lower-rim amide groups.