Eur. Phys. J. D 43, 37-40 (2007)
https://doi.org/10.1140/epjd/e2007-00070-4

Coordination and solvation of noble metal ions: Infrared spectroscopy of Ag⁺(H₂O)_n

¹ Department of Chemistry, Faculty of Sciences, Kyushu University, Hakozaki, Fukuoka, 812-8581, Japan
² Institute for Molecular Science, Myodaiji, Okazaki, 444-8585, Japan

Corresponding author: ^a kazu.scc@mbox.nc.kyushu-u.ac.jp

Received: 23 July 2006
Revised: 30 October 2006
Published online: 24 May 2007

Abstract

Vibrational spectra of mass-selected Ag⁺(H₂O)_n ions are measured by infrared photodissociation spectroscopy and analyzed with the aid of density functional theory calculations. Hydrogen bonding between H₂O molecules is found to be absent for cold Ag⁺(H₂O)₃, but detected for Ag⁺(H₂O)₄ through characteristic changes in the position and intensity of OH-stretching transitions. The third H₂O coordinates directly to Ag⁺, but the fourth H₂O prefers solvation through hydrogen bonding. The preference of the tri-coordinated form is attributed to the inefficient 5s–4d hybridization in Ag⁺, in contrast to the efficient 4s–3d hybridization in Cu⁺. For Ag⁺(H₂O)₄, however, di-coordinated isomers are identified in addition to the tri-coordinated one.