C-H···π interactions disrupt electrostatic interactions between non-aqueous electrolytes to increase solubility

Sharmila Samaroo; Charley Hengesbach; Chase Bruggeman; Nunzio Giorgio G Carducci; Lincoln Mtemeri; Richard J Staples; Thomas Guarr; David P Hickey

doi:10.1038/s41557-023-01291-1

C-H···π interactions disrupt electrostatic interactions between non-aqueous electrolytes to increase solubility

Nat Chem. 2023 Oct;15(10):1365-1373. doi: 10.1038/s41557-023-01291-1. Epub 2023 Aug 14.

Authors

Sharmila Samaroo¹, Charley Hengesbach², Chase Bruggeman¹, Nunzio Giorgio G Carducci¹, Lincoln Mtemeri¹, Richard J Staples³, Thomas Guarr^{4

5}, David P Hickey⁶

Affiliations

¹ Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI, USA.
² Michigan State University Bioeconomy Institute, Michigan State University, Holland, MI, USA.
³ Department of Chemistry, Michigan State University, East Lansing, MI, USA.
⁴ Michigan State University Bioeconomy Institute, Michigan State University, Holland, MI, USA. guarrt@msu.edu.
⁵ Jolt Energy Storage Technologies, LLC, Holland, MI, USA. guarrt@msu.edu.
⁶ Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI, USA. hickeyd6@msu.edu.

PMID: 37580445
DOI: 10.1038/s41557-023-01291-1

Abstract

Grid-scale energy storage applications, such as redox flow batteries, rely on the solubility of redox-active organic molecules. Although redox-active pyridiniums exhibit exceptional persistence in multiple redox states at low potentials (desirable properties for energy storage applications), their solubility in non-aqueous media remains low, and few practical molecular design strategies exist to improve solubility. Here we convey the extent to which discrete, attractive interactions between C-H groups and π electrons of an aromatic ring (C-H···π interactions) can describe the solubility of N-substituted pyridinium salts in a non-aqueous solvent. We find a direct correlation between the number of C-H···π interactions for each pyridinium salt and its solubility in acetonitrile. The correlation presented in this work highlights a consequence of disrupting strong electrostatic interactions with weak dispersion interactions, showing how minimal structural change can dramatically impact pyridinium solubility.