Ion Association in Lanthanide Chloride Solutions
| Autor: | John H. Harding, Sébastien Lectez, Stephen Stackhouse, Colin L. Freeman, Aaron R. Finney |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
Lanthanide
ion pairing Full Paper 010405 organic chemistry Chemistry Organic Chemistry Lanthanides | Hot Paper potential of mean force General Chemistry Inner sphere electron transfer Ion-association Full Papers 010402 general chemistry 01 natural sciences Catalysis molecular dynamics 0104 chemical sciences Solvent Molecular dynamics Chemical physics Outer sphere electron transfer lanthanides Potential of mean force Anion binding rare-earth elements |
| Zdroj: | Chemistry (Weinheim an Der Bergstrasse, Germany) |
| ISSN: | 1521-3765 0947-6539 |
| Popis: | A better understanding of the solution chemistry of the lanthanide (Ln) salts in water would have wide ranging implications in materials processing, waste management, element tracing, medicine and many more fields. This is particularly true for minerals processing, given governmental concerns about lanthanide security of supply and the drive to identify environmentally sustainable processing routes. Despite much effort, even in simple systems, the mechanisms and thermodynamics of LnIII association with small anions remain unclear. In the present study, molecular dynamics (MD), using a newly developed force field, provide new insights into LnCl3(aq) solutions. The force field accurately reproduces the structure and dynamics of Nd3+, Gd3+ and Er3+ in water when compared to calculations using density functional theory (DFT). Adaptive‐bias MD simulations show that the mechanisms for ion pairing change from dissociative to associative exchange depending upon cation size. Thermodynamics of association reveal that whereas ion pairing is favourable, the equilibrium distribution of species at low concentration is dominated by weakly bound solvent‐shared and solvent‐separated ion pairs, rather than contact ion pairs, reconciling a number of contrasting observations of LnIII–Cl association in the literature. In addition, we show that the thermodynamic stabilities of a range of inner sphere and outer sphere LnClx(3-x)+ coordination complexes are comparable and that the kinetics of anion binding to cations may control solution speciation distributions beyond ion pairs. The techniques adopted in this work provide a framework with which to investigate more complex solution chemistries of cations in water. |
| Databáze: | OpenAIRE |
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