Multiple stimuli triggered structural isomerization of copper iodide–pyridine crystals

Abstract

Copper based coordination materials possess the ability to change their physico-chemical properties in response to external stimuli. Recent studies related to Cu(I) complexes have revealed the external stimuli triggered luminescence variations such as thermochromism, vapochromism, and mechanochromism, during which the underlying mechanism was attributed to the appearance of various polymorphs. However about the structural isomerization between the structural isomers proceeding on a concrete crystal, researchers still lack a deep understanding of the morphology evolution in a stimulus-based isomerization process. In this study, we dug into the structural isomerization process in the representative copper iodide coordination crystals of [CuI(py)]_n (py = pyridine) and [CuI(py)]₄. Under multiple stimuli such as heat, mechanical force and solvent annealing, the “chain” cluster of [CuI(py)]_n was found to convert into the “cubane” cluster of [CuI(py)]₄, exhibiting high contrast photoluminescence from blue to yellow. Systematic comparative studies and detailed analysis of the interface evolution during isomerization in single crystals reveal an underlying conversion mechanism of the dissociation–reorganization process. Such a deep understanding of the structural isomerization would facilitate real applications of multi-stimuli responsive Cu(I) complexes.