Redox Property Tuning in Bipyridinium Salts

Zuzana Burešová; Milan Klikar; Petr Mazúr; Michaela Mikešová; Jaroslav Kvíčala; Tomas Bystron; Filip Bureš

doi:10.3389/fchem.2020.631477

Redox Property Tuning in Bipyridinium Salts

Front Chem. 2021 Jan 27:8:631477. doi: 10.3389/fchem.2020.631477. eCollection 2020.

Authors

Zuzana Burešová¹, Milan Klikar¹, Petr Mazúr², Michaela Mikešová², Jaroslav Kvíčala³, Tomas Bystron⁴, Filip Bureš¹

Affiliations

¹ Institute of Organic Chemistry and Technology, Faculty of Chemical Technology, University of Pardubice, Pardubice, Czechia.
² Department of Chemical Engineering, Faculty of Chemical Engineering, University of Chemistry and Technology Prague, Prague, Czechia.
³ Department of Organic Chemistry, Faculty of Chemical Technology, University of Chemistry and Technology Prague, Prague, Czechia.
⁴ Department of Inorganic Technology, Faculty of Chemical Technology, University of Chemistry and Technology Prague, Prague, Czechia.

Abstract

Bipyridinium salts are currently very popular due to their perspective applications in redox flow batteries. Hence, we designed and prepared a series of bipyridiniums based on 2,2'-, 3,3'-, and 4,4'-bipyridine and 2,2'-bipyrimidine. The straightforward synthesis utilizes commercially or readily available starting compounds and their direct N-alkylation, mostly using 1,3-propanesultone. All eleven target derivatives with systematically evolved structure were investigated by cyclic voltammetry, which allowed elucidating thorough structure-property relationships. The electrochemical behavior depends primarily on the parent scaffold, type of N-alkylation, number of quaternized nitrogen atoms, planarity, counter ion as well as the used media. Two derivatives featuring quasi-reversible redox processes were further tested on rotating disc electrode and in a flow battery half-cell. 4,4'-Bipyridinium derivative bearing two sultone residues showed better performance and stability in the flow half-cell with small capacity decays of 0.09/0.15% per reduction-oxidation cycle, based on the number of the utilized redox processes (one/two).

Keywords: bipyridine; bipyridinium; electrochemistry; property tuning; redox flow battery; synthesis.