Mechanochromic and thermochromic luminescence of a copper iodide cluster

The mechanochromic and thermochromic luminescence properties of a molecular copper(I) iodide cluster formulated [Cu₄I₄(PPh ₂(CH₂CH=CH₂))₄] are reported. Upon mechanical grinding in a mortar, its solid-state emission properties are drastically modified as well as its thermochromic behavior. This reversible phenomenon has been attributed to distortions in the crystal packing leading to modifications of the intermolecular interactions and thus of the [Cu ₄I₄] cluster core geometry. Notably, modification of the Cu-Cu interactions seems to be involved in this phenomenon directly affecting the emissive properties of the cluster.