TY - JOUR
T1 - Electrode Kinetics of the Redox Reaction of Tris(2,2′-bipyridine) nickel Complexes in an Ionic Liquid
AU - Katayama, Yasushi
AU - Toshimitsu, Yuichi
AU - Miura, Takashi
N1 - Funding Information:
Part of this study was financially supported by MEXT-Supported Program for the Strategic Research Foundation at Private Universities, 2012-2016.
PY - 2014/6/10
Y1 - 2014/6/10
N2 - Electrode reaction of tris(2,2′-bipyridine)nickel complexes, [Ni(bpy)3]3+ and [Ni(bpy)3]2+, was investigated in an aprotic ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA) using AC impedance spectroscopy. The formal potential of [Ni(bpy)3]3+/2+ was 1.37 V vs. ferrocene/ferrocenium at 25 °C. The diffusion coefficients of [Ni(bpy) 3]3+ and [Ni(bpy)3]2+ at 25°C were 4.2 and 7.0 × 10-8 cm2 s-1, respectively, which are close to those of [M(bpy)3]3+ and [M(bpy)3]2+ (M = Ru and Fe) due to the similarity in the charge densities. The activation energies for the diffusion coefficients were close to that for the viscosity of the ionic liquid, indicating the viscosity is a major factor that determine the diffusion of the complexes. The rate constant of [Ni(bpy)3]3+/2+ was 8.3 × 10-6 cm s-1, which is smaller by two orders of magnitude than those for [Ru(bpy)3]3+/2+ and [Fe(bpy)3]3+/2+, reflecting the slow electron transfer caused by participation of the anti-bonding molecular orbital in the redox reaction. The apparent activation energy for the rate constant of [Ni(bpy)3]3+/2+ is considered determined not only by the activation energy for the viscosity but also by the reorganization energy, of which the inner component is larger than those in [Ru(bpy)3]3+/2+ and [Fe(bpy)3] 3+/2+.
AB - Electrode reaction of tris(2,2′-bipyridine)nickel complexes, [Ni(bpy)3]3+ and [Ni(bpy)3]2+, was investigated in an aprotic ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA) using AC impedance spectroscopy. The formal potential of [Ni(bpy)3]3+/2+ was 1.37 V vs. ferrocene/ferrocenium at 25 °C. The diffusion coefficients of [Ni(bpy) 3]3+ and [Ni(bpy)3]2+ at 25°C were 4.2 and 7.0 × 10-8 cm2 s-1, respectively, which are close to those of [M(bpy)3]3+ and [M(bpy)3]2+ (M = Ru and Fe) due to the similarity in the charge densities. The activation energies for the diffusion coefficients were close to that for the viscosity of the ionic liquid, indicating the viscosity is a major factor that determine the diffusion of the complexes. The rate constant of [Ni(bpy)3]3+/2+ was 8.3 × 10-6 cm s-1, which is smaller by two orders of magnitude than those for [Ru(bpy)3]3+/2+ and [Fe(bpy)3]3+/2+, reflecting the slow electron transfer caused by participation of the anti-bonding molecular orbital in the redox reaction. The apparent activation energy for the rate constant of [Ni(bpy)3]3+/2+ is considered determined not only by the activation energy for the viscosity but also by the reorganization energy, of which the inner component is larger than those in [Ru(bpy)3]3+/2+ and [Fe(bpy)3] 3+/2+.
KW - AC impedance
KW - Electrode kinetics
KW - Ionic liquid
KW - Tris(2;2′-bipyridine)nickel complex
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U2 - 10.1016/j.electacta.2013.12.087
DO - 10.1016/j.electacta.2013.12.087
M3 - Article
AN - SCOPUS:84901235248
SN - 0013-4686
VL - 131
SP - 36
EP - 41
JO - Electrochimica Acta
JF - Electrochimica Acta
ER -