Atomically precise metal clusters are nanoscale molecules made up of a specific number of metal centers and peripheral ligands, showing well-defined structures. In addition, by leveraging the structural tunability and dynamic responsiveness provided by their well-defined atomic arrangements, as well as the dynamic and reversible nature of coordination bonds and metal–metal interactions, these clusters have been directly used to construct artificial systems that mimic natural stimuli-responsive processes. Although major advances have been achieved in understanding stimuli-responsive structural isomerization in gold and silver clusters, research on polynuclear copper clusters is still underexplored.
A joint research team led by Prof. YAN Liangliang from Fujian Institute of Research on the Structure of Matter (FJIRSM), Chinese Academy of Sciences and Prof. Vivian Wing‑Wah YAM from the University of Hong Kong has reported solvent‑ and temperature‑driven reversible isomerization between twocubic octanuclear copper(I) cluster isomers, Cu8‑1 and Cu8‑2. This study has been published in PNAS.
The team designed a phosphine‑alkyne bifunctional ligand, (2‑ethynylphenyl)diphenylphosphine (HL), to synthesize Cu8‑1. Single‑crystal X‑ray diffraction, high‑resolution electrospray‑ionization mass spectrometry (HR‑ESI‑MS) and nuclear magnetic resonance (NMR) measurements confirmed its atomic‑level structure. Within this structure, six Cu atoms are protected by both P and C≡C donors, whereas the remaining two are solely protected by C≡C donors, thereby presenting accessible sites for further functional group coordination.
Further research has revealed that the introduction of external stimuli, including varying solvent compositions or temperatures, could induce a reversible structural transformation between Cu8-1 and its isomer, Cu8-2, which is achieved through the cleavage of the original Cu–P coordination bonds and the re-coordination of phosphine with exposed Cu sites. It is important to note that this process preserves the Cu8 kernel structure.
Accompanying the structural switch, distinct luminescence changes take place. Cu8-1 emits green light at 520 nm, while Cu8-2 produces red emission at 625 nm. Tunable emission colour can be visually observed by adjusting solvent ratios under ultraviolet excitation.
This study demonstrates a feasible ligand‑design strategy to introduce dynamic responsiveness for copper(I) clusters. It establishes a valuable model system to probe structure‑property correlations, paving the way for future molecular switches, chemical sensors and luminescent smart materials.
Reversible isomerization between Cu8‑1 and Cu8‑2 and their solvent‑tunable luminescence colour switching (Image by Prof. YAN's group)
Contact:
Prof. YAN Liangliang
Fujian Institute of Research on the Structure of Matter
Chinese Academy of Sciences
Email: yanll@fjirsm.ac.cn
