Evaluation of Tris-Bipyridine Chromium Complexes for Flow Battery Applications: Impact of Bipyridine Ligand Structure on Solubility and Electrochemistry

This report describes the design,
synthesis, solubility, and electrochemistry of a series of tris-bipyridine
chromium complexes that exhibit up to six reversible redox couples
as well as solubilities approaching 1 M in acetonitrile. We have systematically
modified both the ligand structure and the oxidation state of these
complexes to gain insights into the factors that impact solubility
and electrochemistry. The results provide a set of structure–solubility–electrochemistry
relationships to guide the future development of electrolytes for
nonaqueous flow batteries. In addition, we have identified a promising
candidate from the series of chromium complexes for further electrochemical
and battery assessment.