Ammonia Solvation of Alkaline Earth Dications: Mg(II), Ca(II), Sr(II), and Ba(II); Hybrid Density Functional Theory Born–Oppenheimer Molecular Dynamics Studies

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2023-04, Vol.127 (15), p.3317-3329
• Main Authors: León-Pimentel, C. I., Saint-Martin, H., Ramírez-Solís, A.
• Format: Article
• Language: English
• Subjects: A: Structure, Spectroscopy, and Reactivity of Molecules and Clusters
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/acs.jpca.2c08432

Structural and dynamical properties of Sr2+ and Ba2+ dications in ammonia microsolvation environments were studied through hybrid density functional theory Born-Oppenhemier molecular dynamics of [Sr­(NH3) n ]2+ and [Ba­(NH3) n ]2+ clusters with n = 2, 3, 4, 5, 6, 8, 10, and 27. The largest cluster models were used to explore bulk phase solvation of Sr2+ and Ba2+ in liquid ammonia for which experimental data are available. Results are discussed in the light of previous results obtained for the [Mg­(NH3) n ]2+ and [Ca­(NH3) n ]2+ systems with the same methodology. Vibrational and EXAFS spectra are reported for the first time for [Sr­(NH3) n ]2+ and [Ba­(NH3) n ]2+ systems. It was found that alkaline earth dications have coordination numbers (CN) in ammonia as follows: Mg2+ (6) < Ca2+ (8) < Sr2+ (8.3) < Ba2+ (9.4). The coordination structures found turn out to be rather flexible with CN greater than six and these structures depart from the simple geometry of hexamine in the solid phase.