Molecular Dynamics Investigation of Water-Exchange Reactions on Lanthanide Ions in water/1-ethyl-3-methylimidazolium Trifluoromethylsufate ([EMIm][OTf])

Yi-Jung Tu, Zhijin Lin, Matthew J Allen, G Andrés Cisneros

J Chem Phys. 2018 Jan 14;148(2):024503.

PMID: 29331119

Abstract:

We report a kinetic study of the water exchange on lanthanide ions in water/[1-ethyl-3-methylimidazolium][trifluoromethylsufate] (water/[EMIm][OTf]). The results from 17O-NMR measurements show that the water-exchange rates in water/[EMIm][OTf] increase with decreasing size of the lanthanide ions. This trend for water-exchange is similar to the previously reported trend in water/1-ethyl-3-methylimidazolium ethyl sulfate (water/[EMIm][EtSO4]) but opposite to that in water. To gain atomic-level insight into these water-exchange reactions, molecular dynamics simulations for lanthanide ions in water/[EMIm][OTf] have been performed using the atomic-multipole-optimized-energetics-for-biomolecular-application polarizable force field. Our molecular dynamics simulations reproduce the experimental water-exchange rates in terms of the trend and provide possible explanations for the observed experimental behavior. The smaller lanthanide ions in water/[EMIm][OTf] undergo faster water exchange because the smaller lanthanide ions coordinate to the first shell [OTf]- anions more tightly, resulting in a stronger screening effect for the second-shell water. The screening effect weakens the interaction of the lanthanide ions with the second-shell water molecules, facilitating the dissociation of water from the second-shell and subsequent association of water molecules from the outer solvation shells.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP342573755	1-Ethyl-3-methylimidazolium ethyl sulfate		342573-75-5	Price