Hypercarbon‐Centered Gold(I)‐Copper(I) Clusters Exhibiting a Dissolution/Crystallization‐Induced Photoluminochromism

ABSTRACT Chemical molecules may show very different properties in the solid state and in solution, which is mainly caused by the difference in structure between different physical states. Well‐defined metal cluster molecules are ideal models for the investigation of the dynamic dissolution/crystallization process, as they usually exhibit photoluminescence (PL) that is sensitive to reversible changes in coordination geometry and multi‐electron structure. Here we report the dissolution/crystallization‐induced photoluminochromism (PLC) of carbon‐centered Au I 6 Cu I 2 clusters bearing pyridylphosphine or pyridyl N ‐heterocyclic carbene (NHC) ligands. These clusters, with an octahedral structure doubly capped with copper(I), exhibit greenish‐yellow emission in the solid state. Remarkably, the PL of the NHC‐protected clusters in solution changes only slightly, whereas the phosphine‐protected clusters exhibit red PL accompanied by a large bathochromic shift (>100 nm), a reversible process upon dissolution equilibration. X‐ray absorption spectroscopy and theoretical calculations suggest that the octahedral CAu I 6 structure in the crystal is twisted into a triangular prismatic structure in solution. This remarkable ligand effect on the dissolution/crystallization‐induced PLC would provide advanced design guidance for stimuli‐responsive chromic materials.