Study of the Elusive Hydration of Pb 2+ from the Gas Phase to the Liquid Aqueous Solution: Modeling the Hemidirected Solvation with a Polarizable MCDHO Force-Field

• Published in: The journal of physical chemistry. B Vol. 123; no. 43; pp. 9155 - 9166
• Main Authors: León-Pimentel, C I, Martínez-Jiménez, M, Saint-Martin, H
• Format: Journal Article
• Language: English
• Published: United States 31-10-2019
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/acs.jpcb.9b04541

The Pb
presents unique hydration features that make the experimental characterization and its theoretical modeling challenging: classical molecular dynamics (MD) with standard force-fields fails to produce the experimentally determined diffusion coefficient and the EXAFS spectrum. Here we study the hydration of Pb
in aqueous solution employing a polarizable model compatible with the MCDHO water model. The MCDHO FF for the Pb
-water interaction was fitted to reproduce the configurations and interaction energies of various [Pb(H
O)
]
clusters obtained with ab initio calculations, with
= 4, 6, and 8. Its use in classical MD simulations yielded qualitative agreement with Born-Oppenheimer molecular dynamics of gas-phase hydrated clusters and MD simulations of the aqueous solution resulted in good agreement with the experimental
and EXAFS spectrum. Analysis of the MD trajectories revealed a labile and very dynamic hemidirected first hydration shell in the aqueous solution with a non-well-defined coordination number CN; nonetheless, it was found that the more probable hydration structures have either 3 or 4 water molecules directly bound to the Pb
with another 3 or 2 at slightly larger distances. The simulations of the gas-phase [Pb(H
O)
]
cluster were found to capture the main structural features of the diluted aqueous solution.