How Does CeIII Nitrate Dissolve in a Protic Ionic Liquid? A Combined Molecular Dynamics and EXAFS Study
Abstract
A diluted solution of Ce(NO3)3 in the protic ionic liquid (IL) ethylammonium nitrate (EAN) was investigated using molecular dynamics (MD) simulations and extended X-ray absorption fine structure (EXAFS) spectroscopy. For the first time polarizable effects were included in the MD force field to describe a heavy metal ion in a protic IL, but, unlike water, they were found to be unessential. The CeIII ion first solvation shell is formed by nitrate ions arranged in an icosahedral structure, and an equilibrium between monodentate and bidentate ligands is present in the solution. By combining distance and angular distribution functions it was possible to unambiguously identify this peculiar coordination geometry around the ions dissolved in solution. The metal ions are solvated within the polar domains of the EAN nanostructure and the dissolved salt induces almost no reorganization of the pre-existing structure of EAN upon solubilization.
Keywords
Protic ionic liquids
Molecular dynamics simulations
Lanthanoid ions
Coordination geometry
Extended Xray absorption fine structure (EXAFS) spectroscopies
Icosahedral structure
Cerium compounds
Existing structure
Bidentate ligands
X ray absorption
Nitrates
Molecular dynamics
Metal ions
Ligands
Extended X ray absorption fine structure spectroscopy
Distribution functions
Heavy metals
Ionic liquids
Angular distribution