Transformations in Chemically Responsive Copper-Calixarene Architectures.

Self-assembly of bis-picolyl-appended calix[4]arene (L) with CuI or CuII 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 CuI2 L2 Br2 (1) and CuI2 L2 I2 (3) that were transformed into tetranuclear assemblies CuI4 L2 Br4 (2) and CuI4 L2 I4 (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 CuCl2 produced macrocycle CuII2 L2 Cl4 (5), which crystallised as cage [CuII2 L4 (μ-Cl)]3+ (6) in the presence of MeOH. Two chemical signals-introduction of CuCl2 and addition of CH3 CN-regenerated macrocycle 5. Coordination of L to Cu(OTf) yielded macrocycle CuI2 L2 (OTf)2 (7) that also crystallised as cage 6 upon oxidation in CHCl3 .