Reversible Transformation between Cubane and Stairstep Cu4I4 Clusters Using Heat or Solvent Vapor

The controlled self-assembly of CuI and an asymmetric ligand with mixed N/S donors, 2-(tert-butyl-thio)-N-(pyridin-3-yl)acetamide (L), afforded three CuI coordination polymers (CPs), [Cu4I4L2(MeCN)(2)](n) (1), [Cu4I4L2](n) (2), and {[Cu4I4L2]center dot MeOH}(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 Cu4I4 cluster, whereas CPs 2 and 3 are composed of cubane-like Cu4I4 clusters. Crystal-to-crystal transformations of 1 to 2 and 3 showed reversible transformations between different Cu4I4 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.