Reversible Crystal Transformations And Luminescence Vapochromism By Fast Guest Exchange In Cu(I) Coordination Polymers

Six Cu(I) coordination polymers (CPs)-[Cu2I2L2] (1), {[Cu2I2L2]center dot 2MeCN}(n) (2), [Cu4I4L2](n) (3), {[Cu4I4L2]center dot CH2Cl2}(n) (4), {[Cu4I4L2]center dot CHCl3}(n) (5), and {[Cu4I4L2]center dot C6H6}(n) (6) were synthesized by self-assembly reactions of CuI and the flexible mixed N/S donor ligand 4-(2-(cyclohexylthio)ethoxy)pyridine (L). Single-crystal X-ray diffraction analyses reveal that these 1D CPs form sets of supramolecular isomers; 1 and 2 are based on Cu2I2 rhomboids, while 3-6 are based on cubane Cu4I4 clusters. Crystal-to-crystal transformations of CPs 1-6 were reversible under heat or in an appropriate solvent (acetonitrile, dichloromethane, chloroform, or benzene). In addition, crystal transformations between CPs 1 and 3 occurred through addition of L or CuI. Moreover, CPs 3-6 exhibited reversible guest exchange and crystal transformations on exposure to the vapor of volatile organic compounds and heat. Remarkably, a guest molecule was exchanged by other guest molecules in the vapor phase within very short times and without the use of acetonitrile as a solvent, which normally plays a key role in trapped solvent exchange experiments.