Synthesis and structural determination of multidentate 2,3-dithiol-stabilized Au clusters

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• Interface bond structure is an understudied factor influencing nanomaterial properties, alongside quantum confinement.
• Thiol-bridging motifs, like those in monothiol-stabilized gold nanoclusters, inspired the use of dithiol ligands.
• 2,3-dimercaptopropanesulfonic (DMPS) acid was employed to synthesize dithiol-protected gold clusters (DTCs).

Purpose of the Study:

• To investigate the structural and property effects of dithiol ligands on gold clusters.
• To probe the entropy gain of dithiol versus monothiol ligand protection.
• To examine constraints on thiol bridging surface bonding in DTCs.

Main Methods:

• Diffusion nuclear magnetic resonance (NMR) for hydrodynamic size estimation.
• Atomic force microscopy (AFM) for size distribution and core-ligand confirmation.
• Mass spectrometry, thermogravimetric analysis (TGA), infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS) for characterization.

Main Results:

• Size-dependent optical properties were observed in the synthesized Au DTCs.
• Pure Au(4) clusters exhibited a characteristic absorbance band at 282 nm.
• Detailed structural and bonding information (Au-S) of Au(4) clusters was elucidated using various 2D NMR techniques, IR, and XPS.

Conclusions:

• Dithiol ligand protection offers unique structural and bonding characteristics compared to monothiol protection.
• A potential structure for Au(4) clusters was proposed, requiring further theoretical and experimental validation.
• This research highlights the importance of interface bonding in tuning nanomaterial properties.