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Ion association with tetra-n-alkylammonium cations stabilizes higher-oxidation-state neptunium dioxocations.

ABSTRACT: Extended-coordination sphere interactions between dissolved metals and other ions, including electrolyte cations, are not known to perturb the electrochemical behavior of metal cations in water. Herein, we report the stabilization of higher-oxidation-state Np dioxocations in aqueous chloride solutions by hydrophobic tetra-n-alkylammonium (TAA⁺) cations-an effect not exerted by fully hydrated Li⁺ cations under similar conditions. Experimental and molecular dynamics simulation results indicate that TAA⁺ cations not only drive enhanced coordination of anionic Cl^- ligands to Np^V/VI but also associate with the resulting Np complexes via non-covalent interactions, which together decrease the electrode potential of the Np^VI/Np^V couple by up to 220?mV (??G?=?-22.2?kJ?mol^-1). Understanding the solvation-dependent interplay between electrolyte cations and metal-oxo species opens an avenue for controlling the formation and redox properties of metal complexes in solution. It also provides valuable mechanistic insights into actinide separation processes that widely use quaternary ammonium cations as extractants or in room temperature ionic liquids.

SUBMITTER: Estes SL

PROVIDER: S-EPMC6320366 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature

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Ion association with tetra-n-alkylammonium cations stabilizes higher-oxidation-state neptunium dioxocations.

Estes Shanna L SL Qiao Baofu B Jin Geng Bang GB

Nature communications 20190104 1

Extended-coordination sphere interactions between dissolved metals and other ions, including electrolyte cations, are not known to perturb the electrochemical behavior of metal cations in water. Herein, we report the stabilization of higher-oxidation-state Np dioxocations in aqueous chloride solutions by hydrophobic tetra-n-alkylammonium (TAA<sup>+</sup>) cations-an effect not exerted by fully hydrated Li<sup>+</sup> cations under similar conditions. Experimental and molecular dynamics simulatio ...[more]

PMID: 30610189

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Ion association with tetra-n-alkylammonium cations stabilizes higher-oxidation-state neptunium dioxocations.

Publications

Ion association with tetra-n-alkylammonium cations stabilizes higher-oxidation-state neptunium dioxocations.

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