Recommendations on reporting electrode potentials in nonaqueous solvents

This report recommends that the redox couples ferrocene/ferricenium ion [ferrocene: bis(η-cyclopentadienyl) iron(II)] and bis(biphenyl)chromium(I)/bis(biphenyl)chromium(O) be employed as reference redox systems. Procedures for measuring and reporting electrode potentials in nonaqueous solvents versus these reference redox systems are presented. The difference in electrode potentials for ferrocene/ferricenium ion and bis(biphenyl)chromium(O)/bis(biphenyl)chromium(I) ion for 22 solvents obtained by polarography and cyclic voltammetry are listed. Both of the recommended redox systems approach a solvent independent redox system as closely as presently known. Electrode potential data reported versus these systems permit the comparison of electrode potentials for a given system in different nonaqueous solvents and thus allow studies of solvent effects on electrode potentials in nonaqueous systems by compiling and comparing data obtained in different solvents.