Phosphine Oxide-Functionalized Terthiophene Redox Systems

Main group systems capable of undergoing controlled redox events at extreme potentials are elusive yet highly desirable for a range of organic electronics applications including use as energy storage media. Herein we describe phosphine oxide-functionalized terthiophenes that exhibit two reversible 1e(-) reductions at potentials below -2 V vs Fc/Fc(+) (Fc=ferrocene) while retaining high degrees of stability. A phosphine oxide-functionalized terthiophene radical anion was synthesized in which the redox-responsive nature of the platform was established using combined structural, spectroscopic, and computational characterization. Straightforward structural modification led to the identification of a derivative that exhibits exceptional stability during bulk 2 e(-) galvanostatic charge-discharge cycling and enabled characterization of a 2 e(-) redox series. A new multi-electron redox system class is hence disclosed that expands the electrochemical cell potential range achievable with main group electrolytes without compromising stability.

Automated summary

In this study, phosphine oxide-functionalized terthiophenes were demonstrated to undergo reversible 1e(-) reductions at potentials below -2 V vs Fc/Fc(+) (Fc=ferrocene) while maintaining high stability. By modifying the structure, a derivative was identified that showed exceptional stability during bulk 2 e(-) galvanostatic charge-discharge cycling and enabled characterization of a 2 e(-) redox series. This work unveils a new class of multi-electron redox systems that expands the potential range achievable with main group electrolytes without compromising stability.