Transformations in Chemically Responsive Copper‐Calixarene Architectures

Self‐assembly of bis‐picolyl‐appended calix[4]arene ( L ) with Cu I or Cu II 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 I 2 L 2 Br 2 ( 1 ) and Cu I 2 L 2 I 2 ( 3 ) that were transformed into tetranuclear assemblies Cu I 4 L 2 Br 4 ( 2 ) and Cu I 4 L 2 I 4 ( 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. Assembly of L with CuCl 2 produced macrocycle Cu II 2 L 2 Cl 4 ( 5 ), which crystallised as cage [Cu II 2 L 4 (μ‐Cl)] 3+ ( 6 ) in the presence of MeOH. Two chemical signals—introduction of CuCl 2 and addition of CH 3 CN—regenerated macrocycle 5 . Coordination of L to Cu(OTf) yielded macrocycle Cu I 2 L 2 (OTf) 2 ( 7 ) that also crystallised as cage 6 upon oxidation in CHCl 3 .