Coordination and Solvation in Gas-Phase Ag⁺(C₂H₂) Complexes Studied with Selected-Ion Infrared Spectroscopy

Area of Science:

• Physical Chemistry
• Inorganic Chemistry
• Spectroscopy

Background:

• Metal-acetylene complexes are crucial in catalysis and materials science.
• Understanding the coordination chemistry of coinage metals (Ag, Cu, Au) with unsaturated hydrocarbons provides fundamental insights.

Purpose of the Study:

• To investigate the structure and bonding of silver-acetylene cation complexes.
• To compare the coordination behavior of Ag+ with Cu+ and Au+.

Main Methods:

• Production of silver-acetylene cation complexes (Ag+(C2H2)n, n=1-9) via laser ablation.
• Infrared laser photodissociation spectroscopy in the C-H stretching region.
• Density functional theory (DFT) calculations.

Main Results:

• Four acetylene ligands strongly coordinate to the silver cation in smaller complexes (n=1-4).
• Ag+(C2H2)n complexes exhibit η2-bonded, cation-π interactions with red-shifted C-H stretches.
• Silver cation displays tetrahedral coordination, accommodating four acetylene ligands, unlike Cu+ and Au+.

Conclusions:

• Silver cation uniquely forms stable, tetrahedrally coordinated complexes with four acetylene ligands.
• Solvation of the Ag+(C2H2)4 core with additional acetylene molecules leads to distinct spectral patterns.
• The study provides valuable insights into the coordination chemistry and bonding of silver-acetylene complexes.