Redox Reaction of Some Nitroxyl Radicals in 1-Butyl-1-Methylpyrrolidinium Bis(fluorosulfonyl)amide in the Presence and Absence of Lithium Ion

The electrochemical behavior of 2,2,6,6,-tetramethylpiperidine-1-oxyl (TEMPO) and 4-oxo-TEMPO was investigated in 1-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)amide (BMPFSA) in the absence and presence of LiFSA. The redox reactions of TEMPO + /TEMPO and 4-oxo-TEMPO + /4-oxo-TEMPO were observed on a platinum electrode in the absence and presence of 0.5 M LiFSA. The formal potentials of TEMPO + /TEMPO and 4-oxo-TEMPO + /4-oxo-TEMPO were positively shifted in the presence of LiFSA, indicating that the interaction of TEMPO and 4-oxo-TEMPO with Li + altered the energies of the singly occupied molecular orbitals of TEMPO and 4-oxo-TEMPO. The diffusion coefficients and standard rate constants were evaluated by chronoamperometry and electrochemical impedance spectroscopy, respectively. The diffusion coefficient and the standard rate constant were suggested to be controlled not only by the viscosity but also by the interaction between the nitroxyl radicals and Li + .