Reversible Luminescence Vapochromism and Crystal-to-Amorphous-to-Crystal Transformations of Pseudopolymorphic Cu(I) Coordination Polymers

Abstract

Four solvent-responsive one-dimensional copper­(I) coordination polymers (CPs), namely, {[Cu₄I₄<b>L</b>(MeCN)₂]­·CH₂Cl₂}_<i>n</i> (<b>1</b>), {[Cu₄I₄<b>L</b>(MeCN)₂]­·CHCl₃}_<i>n</i> (<b>2</b>), {[Cu₄I₄<b>L</b>(MeCN)₂]­·0.5<i>p</i>-xylene}_<i>n</i> (<b>3</b>), and [Cu₄I₄<b>L</b>­(MeCN)₂]_<i>n</i> (<b>4</b>), were prepared by reaction of CuI with <i>N</i>,<i>N</i>′-bis­[2-(cyclohexylthio)­ethyl]­pyromellitic diimide (<b>L</b>) via self-assembly under varying solvent conditions. CPs <b>1</b>–<b>4</b>, which are pseudopolymorphic supramolecular isomers derived from solvent molecules, are composed of Cu₄I₄ cubane clusters. The ligands in CPs <b>1</b>–<b>3</b> adopted a <i>syn</i>-conformation, whereas in CP <b>4</b> they were observed in the <i>anti</i>-conformation. This occurred via <i>syn</i> to <i>anti</i> transitions upon heating, followed by exposure to MeCN vapor. In addition, a reversible <i>anti</i> to <i>syn</i> transition was achieved by agitating in mixed organic solvents. It was shown that ligand transition from the <i>syn-</i> to the <i>anti</i>-conformation occurred through crystal-to-amorphous-to-crystal transformations. Furthermore, CPs <b>1</b>–<b>3</b> exhibited reversible solvent exchange and crystal transformation by exposure to vapors from volatile organic compounds