Reversible Crystal Transformations and Luminescence Vapochromism by Fast Guest Exchange in Cu(I) Coordination Polymers

Six Cu­(I) coordination polymers (CPs)[Cu₂I₂<b>L</b>₂]_<i>n</i> (<b>1</b>), {[Cu₂I₂<b>L</b>₂]·2MeCN}_<i>n</i> (<b>2</b>), [Cu₄I₄<b>L</b>₂]_<i>n</i> (<b>3</b>), {[Cu₄I₄<b>L</b>₂]·CH₂Cl₂}_<i>n</i> (<b>4</b>), {[Cu₄I₄<b>L</b>₂]·CHCl₃}_<i>n</i> (<b>5</b>), and {[Cu₄I₄<b>L</b>₂]·C₆H₆}_<i>n</i> (<b>6</b>)were synthesized by self-assembly reactions of CuI and the flexible mixed N/S donor ligand 4-(2-(cyclohexylthio)­ethoxy)­pyridine (<b>L</b>). Single-crystal X-ray diffraction analyses reveal that these 1D CPs form sets of supramolecular isomers; <b>1</b> and <b>2</b> are based on Cu₂I₂ rhomboids, while <b>3</b>–<b>6</b> are based on cubane Cu₄I₄ clusters. Crystal-to-crystal transformations of CPs <b>1</b>–<b>6</b> were reversible under heat or in an appropriate solvent (acetonitrile, dichloromethane, chloroform, or benzene). In addition, crystal transformations between CPs <b>1</b> and <b>3</b> occurred through addition of <b>L</b> or CuI. Moreover, CPs <b>3</b>–<b>6</b> 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