Copper(I)-Directed Formation of a Cyclic Pseudorotaxane Tetramer and Its Trimeric Homologue

A matter of concentration: Cyclic pseudorotaxanes are formed by the addition of copper(I) ions to a ligand consisting of a ring containing a chelating unit and, appended to the ring, a rigid fragment containing another chelating unit. The tetramer is formed as the major product in concentrated solution, and the analogous trimer prevails in more dilute solution; both species are connected through a concentration‐dependent slow equilibrium.