Influence of Pyridine on the Unique Multi-Electron Redox Cycle of Nickel Diethyldithiocarbamate

Abstract

Nickel is an intriguing metal for use in multi-electron renewable energy storage due to its high earth-abundance and cost-effective nature. Understanding the redox chemistry of this metal could lead to better redox storage molecules for harvested renewable energy. Unlike traditional one-electron redox couples of first row transition metals, nickel dithiocarbamates exhibit a unique multi-electron redox cycle that could increase energy storage capabilities and power performance of redox flow batteries used for renewable energy storage. Herein, we report mechanistic insight to the nickel diethyldithiocarbamate (NiII(dtc)2) redox cycle and characterization of high valent NiIII and NiIV oxidation states of these complexes by in-depth chemical and electrochemical analyses. These results provide a greater understanding of what enables the unique NiII(dtc)2 redox cycle and the conditions that drive these complexes to undergo one-electron or two-electron transfer reactions. Much of this information is gleaned from the inclusion of an ancillary ligand, pyridine, into the electrochemical cycle and understanding how pyridine enables stabilization of an interesting NiIII intermediate. This greater understanding of NiIII and NiIV chemistry is fundamental in nature and demonstrates the need for further exploration and application of dithiocarbamates in the field of renewable energy storage.