NMR Spectroscopy and Multiscale Modeling Shed Light on Ion–Solvent Interactions and Ion Pairing in Aqueous NaF Solutions

Published

September 10, 2024

Author(s)

Gosia Musial, Demian Riccardi, Chris Suiter, Ethan Sontarp, Samantha Miller, Robert Lirette, Kyle Covington-Rehmeier, Avik Mahata, Chris Muzny, Angela Stelson, Kathleen Schwarz, Jason A. Widegren

Abstract

The balance between ion solvation and ion pairing in aqueous solutions modulates chemical and physical processes from catalysis to protein folding. Yet, despite more than a century of investigation, quantitative determination of the distribution of ion-solvation and ion-pairing states remains elusive. Here, we combine NMR spectroscopy and multiscale modeling to disentangle ion-solvent interactions from ion pairing in aqueous sodium fluoride solutions. We developed a high-accuracy NMR method with external referencing to independently characterize the free ion state as a function of temperature. Experiments and models agree that for free ions, weaker solvation with increasing temperature leads to decreased resonance frequencies. Contrary to conventional assumption, our models predict that both contact and single-solvent-separated ion pairs influence NMR spectral frequency. Our experimental and modeled resonance frequency shifts agree for sodium fluoride solutions with ion pairing, validating our general methodology for differentiating solvation and ion-pairing interactions.

Citation

Journal of Physical Chemistry B

Pub Type

Journals

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Citation

Musial, G. , Riccardi, D. , Suiter, C. , Sontarp, E. , Miller, S. , Lirette, R. , Covington-Rehmeier, K. , Mahata, A. , Muzny, C. , Stelson, A. , Schwarz, K. and Widegren, J. (2024), NMR Spectroscopy and Multiscale Modeling Shed Light on Ion–Solvent Interactions and Ion Pairing in Aqueous NaF Solutions, Journal of Physical Chemistry B, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=956681 (Accessed December 15, 2024)