An N-Heterocyclic-Carbene-Derived Distonic Radical Cation

Nolan M Gallagher; Hong-Zhou Ye; Shuting Feng; Jeffrey Lopez; Yun Guang Zhu; Troy Van Voorhis; Yang Shao-Horn; Jeremiah A Johnson

doi:10.1002/anie.201915534

An N-Heterocyclic-Carbene-Derived Distonic Radical Cation

Angew Chem Int Ed Engl. 2020 Mar 2;59(10):3952-3955. doi: 10.1002/anie.201915534. Epub 2020 Jan 30.

Authors

Nolan M Gallagher¹, Hong-Zhou Ye¹, Shuting Feng^{2

3}, Jeffrey Lopez^{3

4}, Yun Guang Zhu^{3

4}, Troy Van Voorhis¹, Yang Shao-Horn^{3

4}, Jeremiah A Johnson¹

Affiliations

¹ Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA.
² Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA.
³ Research Laboratory of Electronics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA.
⁴ Departments of Mechanical Engineering and Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA.

PMID: 31825136
DOI: 10.1002/anie.201915534

Abstract

We present the discovery of a novel radical cation formed through one-electron oxidation of an N-heterocyclic carbene-carbodiimide (NHC-CDI) zwitterionic adduct. This compound possesses a distonic electronic structure (spatially separate spin and charge regions) and displays persistence under ambient conditions. We demonstrate its application in a redox-flow battery exhibiting minimal voltage hysteresis, a flat voltage plateau, high Coulombic efficiency, and no performance decay for at least 100 cycles. The chemical tunability of NHCs and CDIs suggests that this approach could provide a general entry to redox-active NHC-CDI adducts and their persistent radical ions for various applications.

Keywords: N-heterocyclic carbenes; carbodiimides; cations; radicals; zwitterionic adducts.