Stimuli-induced reversible transformation between isomers of copper(I) clusters sharing an identical core

The construction of reversible structural isomerization in atomically precise metal clusters remains a daunting challenge. Herein, we report the application of a bifunctionalized phosphine-alkyne ligand, (2-ethynylphenyl)diphenylphosphine (HL), to synthesize an octanuclear copper(I) cluster Cu 8 -1 [(Cu 8 (L) 6 (PF 6 ) 2 ], which can undergo a clean and reversible transformation to a Cu 8 -2 isomer responsive to solvent or temperature stimuli. The structural isomerization process has been readily monitored by NMR in solution. Single-crystal X-ray diffraction studies further suggested the possible occurrence of a dynamic ligand rearrangement with reversible Cu–P coordination bond dissociation/reformation with the Cu 8 kernel remained intact. This reversible structural switching is accompanied by a luminescence color change between green (520 nm, Cu 8 -1 ) and red (625 nm, Cu 8 -2 ). This work not only provides a simple approach to achieve stimuli-induced isomerization between Cu 8 -1 and Cu 8 -2 but also offers an ideal platform for investigating their structure–property relationships.