Transformations in Chemically Responsive Copper-Calixarene Architectures.

Self-assembly of bis-picolyl-appended calix[4]arene (L) with Cu or Cu salts resulted in a collection of multinuclear architectures capable of expressing structural reconfigurations in response to various chemical stimuli: addition of copper salt, solvents, or oxidation. Coordination of L to CuX (X=Br, I) selectively yielded dinuclear macrocycles Cu L Br (1) and Cu L I (3) that were transformed into tetranuclear assemblies Cu L Br (2) and Cu L I (4) upon further addition of CuX. These supramolecules persist as robust and discrete entities in solution that display red emission; notably, 4 exhibits luminescence thermochromism.