Reversible Transformation between Cubane and Stairstep Cu sub(4)I sub(4) Clusters Using Heat or Solvent Vapor

The controlled self-assembly of CuI and an asymmetric ligand with mixed N/S donors, 2-(tert-butylthio)-N-(pyridin-3-y l)acetamide (L), afforded three Cu super(I) coordination polymers (CPs), [Cu sub(4)I sub(4)L sub(2)(MeCN) sub(2)] sub(n) (1), [Cu sub(4)I sub(4)L sub(2)] sub(n) (2), and {[Cu sub(4)I sub(4)L sub(2)]MeOH} sub(n) (3). X-ray analyses showed that CPs 1-3 are supramolecular isomers with 1, 2, and 3D structures, respectively. CP 1 adopts a stairstep Cu sub(4)I sub(4) cluster, whereas CPs 2 and 3 are composed of cubane-like Cu sub(4)I sub(4) clusters. Crystal-to-crystal transformations of 1 to 2 and 3 showed reversible transformations between different Cu sub(4)I sub(4) clusters using heat or solvent (acetonitrile or methanol) vapor. CP 2 was reversibly transformed to 3 by the addition of methanol and heat. Therefore, the transformations between supramolecular isomers 1, 2, and 3 are completely reversible. Cluster transformations: Three supramolecular isomeric Cu super(I) coordination polymers showed reversible crystal transformations using solvent vapor or the application of heat (see scheme). Surprisingly, transformations between stairstep and cubane Cu sub(4)I sub(4) clusters were observed during the crystal transformations.