Competitive Pi-Stacking and H-Bond Piling Increase Solubility of Heterocyclic Redoxmers

Publication Title

Journal of Physical Chemistry B

ISSN

15206106

E-ISSN

15205207

Document Type

Article

Abstract

Redoxmers are organic molecules that carry electric charge in flow batteries. In many instances, they consist of heteroaromatic moieties modified with appended groups to prevent stacking of the planar cores and increase solubility in liquid electrolytes. This higher solubility is desired as it potentially allows achieving greater energy density in the battery. However, the present synthetic strategies often yield bulky molecules with low molarity even when they are neat and still lower molarity in liquid solutions. Fortunately, there are exceptions to this rule. Here, we examine one well-studied redoxmer, 2,1,3-benzothiadiazole, which has solubility ∼5.7 M in acetonitrile at 25 °C. We show computationally and prove experimentally that the competition between two packing motifs, face-to-face π-stacking and random N−H bond piling, introduces frustration that confounds nucleation in crowded solutions. Our findings and examples from related systems suggest a complementary strategy for the molecular design of redoxmers for high energy density redox flow cells.

First Page

10409

Last Page

10418

Publication Date

11-19-2020

DOI

10.1021/acs.jpcb.0c07647

PubMed ID

33158362

Department

Department of Chemistry and Biochemistry

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