Solubility-Driven Isolation of a Metastable Nonagold Cluster with Body-Centered Cubic Structure

Area of Science:

• Nanochemistry
• Materials Science
• Physical Chemistry

Background:

• Conventional synthesis of atomically precise gold nanoclusters yields only thermodynamically stable structures.
• Metastable nanoclusters are difficult to isolate and study using standard reduction methods.

Purpose of the Study:

• To develop a novel strategy for the isolation and characterization of metastable gold nanoclusters.
• To investigate the structural and electronic properties of a newly accessible metastable gold cluster.

Main Methods:

• A solubility-driven isolation strategy was employed.
• Electrospray Ionization Mass Spectrometry (ESI-MS) and UV/Vis spectroscopy were used for characterization.
• Density Functional Theory (DFT) calculations were performed to understand electronic properties.

Main Results:

• A metastable gold cluster, [Au9(PPh3)8]+ (1), with a body-centered cubic structure was successfully isolated.
• Cluster 1 was found to be unstable in solution, converting to [Au11(PPh3)8Cl2]+ (2) within 90 minutes.
• DFT calculations confirmed a thermodynamic driving force for the conversion of 1 to 2 due to increased cohesion and larger HOMO-LUMO gap in 2.

Conclusions:

• A biphasic reaction system enabled the concurrent reduction of gold precursors and crystallization of the metastable cluster.
• This work demonstrates a viable strategy for accessing and studying other metastable species in gold nanocluster chemistry.