On the structure of Au₁₁(SR)₉ and Au₁₃(SR)₁₁ clusters

Area of Science:

• Nanomaterials Chemistry
• Computational Chemistry
• Solid State Chemistry

Background:

• Thiolated gold clusters are synthesized using building blocks like Au4, Au6, and Au12, protected by staple motifs.
• Understanding the structural nuances of smaller clusters is crucial for their synthesis and application.

Purpose of the Study:

• To propose and investigate the structures of Au11(SR)9 and Au13(SR)11 clusters, key intermediates in the synthesis of Au15(SR)13.
• To explore the influence of different protecting ligands (H, CH3, phenyl, adamantyl) on cluster core structure and stability.
• To analyze the electronic, optical, and chiroptical properties of these novel gold clusters.

Main Methods:

• Density Functional Theory with Dispersion (DFT-D) calculations were employed to determine cluster structures and energies.
• Investigated the energetic preference between Au3 and Au4 inner cores under various ligand conditions.
• Calculated and discussed predicted IR/Raman, UV-vis absorption, and circular dichroism spectra.

Main Results:

• The Au11(SR)9 cluster preferentially adopts an Au3 inner core, stabilized by dimer and cyclomer motifs, with energetic preference varying by ligand.
• The Au13(SR)11 cluster favors an Au4 inner core, protected by cyclomer, monomer, and dimer motifs.
• Ligand type (e.g., phenyl) can shift the energetic preference towards an Au4 core in Au11(SR)9.
• Energetic differences between Au3 and Au4 cores were quantified for different ligands, highlighting ligand-dependent stability.

Conclusions:

• The Au3 unit is a significant structural component in small thiolated gold clusters.
• The energetic preference for Au3 versus Au4 cores is highly dependent on the nature of the protecting ligands.
• Predicted spectral properties offer avenues for experimental characterization and validation of these proposed structures.