Structures of [Ag7(SR)4]- and [Ag7(DMSA)4]-.

Area of Science:

• Computational chemistry
• Materials science
• Nanotechnology

Background:

• Ligand-protected metal clusters are crucial in catalysis and materials science.
• Determining the lowest-energy structures of these clusters is computationally challenging.
• Previous models for silver clusters like [Ag(7)(SR)(4)](-) suggested different bonding arrangements.

Purpose of the Study:

• To develop and apply a novel genetic algorithm for predicting the global lowest-energy structures of ligand-protected metal clusters.
• To elucidate the ground-state structure of the [Ag(7)(DMSA)(4)](-) cluster.
• To investigate the stability of the -RS-Ag-RS- motif in silver clusters.

Main Methods:

• Development of a genetic algorithm for structure prediction.
• Application of density functional theory (DFT) for energy calculations.
• Simulation of X-ray diffraction patterns for structural validation.

Main Results:

• The ground state of [Ag(7)(DMSA)(4)](-) features eight Ag-S bonds, differing from prior four-bond models.
• The newly predicted structure exhibits significantly lower energy compared to existing models.
• Simulated X-ray diffraction patterns closely match experimental data, validating the computational findings.
• The -RS-Ag-RS- motif is identified as a stable structural element in thiolate-protected silver clusters.
• Lowest-energy structures for [Ag(7)S(4)](-), [Ag(6)S(4)](-), and [Ag(5)S(4)](-) were also predicted.

Conclusions:

• The genetic algorithm combined with DFT is effective for determining global minimum energy structures of metal clusters.
• The [Ag(7)(DMSA)(4)](-) cluster possesses a unique eight-bond silver-sulfur core, challenging previous assumptions.
• The discovery of the stable -RS-Ag-RS- motif provides new insights into the bonding and stability of silver thiolates.