Controlled Synthesis of Diphosphine-Protected Gold Cluster Cations Using Magnetron Sputtering Method

Area of Science:

• Inorganic Chemistry
• Materials Science
• Nanotechnology

Background:

• Precise synthesis of atomically defined gold clusters remains a significant challenge in nanomaterials science.
• Ligand-stabilized gold clusters are crucial for catalysis and electronics, necessitating controlled synthesis methods.
• Polyethylene glycol (PEG) and phosphine ligands like 1,3-bis(diphenylphosphino)propane (dppp) are common in gold chemistry.

Purpose of the Study:

• To achieve the first demonstration of atomically precise synthesis of gold cluster cations.
• To investigate the formation mechanisms of these gold cluster cations using PEG and dppp.
• To characterize the synthesized gold cationic species using spectroscopic and mass spectrometric techniques.

Main Methods:

• Atomically precise synthesis via magnetron sputtering of a gold target onto a solution of PEG and dppp.
• Characterization using UV-vis absorption spectroscopy to identify electronic transitions.
• Characterization using electrospray ionization mass spectrometry (ESI-MS) to determine cluster composition and charge states.

Main Results:

• Successful synthesis of various gold cluster cations, including [Au(dppp)n]+ (n=1,2), [Au2(dppp)n]2+ (n=3,4), [Au6(dppp)n]2+ (n=3,4), and [Au11(dppp)5]3+.
• Identification of [Au(dppp)2]+ as a key intermediate, likely formed through ionization of Au(dppp)2 by PEG.
• Mass spectrometric evidence supports the proposed ionization mechanism involving deprotonated PEG anions.

Conclusions:

• Atomically precise gold cluster cations can be synthesized using magnetron sputtering in the presence of PEG and dppp.
• The [Au(dppp)2]+ cation plays a crucial role as a building block in the formation of larger gold clusters.
• This work establishes a novel pathway for controlled synthesis of ligand-stabilized gold cationic nanostructures.