Ion Solvation Engineering: How to Manipulate the Multiplicity of the Coordination Environment of Multivalent Ions

Scientific Achievement

Advanced free-energy sampling analysis shows that the multiplicity of thermodynamically stable solvation configurations is a general feature of free divalent cations, their ion-pairs and neutral aggregates in low dielectric solvents.  We reveal the macro- and microscopic factors of the solvation multiplicity and show how their interplay can be used to manipulate ion solvation environments and thus the ion solvation-desolvation dynamics.

Significance and Impact

The ability to switch between different solvation environments would enable control over the energetics of metal plating-stripping and charge transfer kinetics. Interestingly, entropic contributions within solvent degrees of freedom are responsible for solvation multiplicity. Temperature, solvent mixing and tuning of ion-solvent interactions can be used to steer the entropic and enthalpic forces to switch between solvation configurations or to create new ones. General rules emerge for creating solutions or polymeric media where one could take advantage of ion solvation multiplicity.

Research Details

  • The results are based on both classical and ab initio molecular dynamics free energy sampling.
  • Effects of temperature, ion-solvent interactions on solvation structures of Mg-cation, MgTFSI+ and MgTFSI2 in THF and diglyme are studied.

A generalization within Marcus Theory to multiple free energy minima is proposed.

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DOI: 10.1021/acs.jpclett.0c02682

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