Fourier-Transformed Large-Amplitude AC Voltammetric Study of Tetrathiafulvalene (TTF): Electrode Kinetics of the TTF0/TTF.+ and TTF.+/TTF2+ Processes



Large-amplitude Fourier-transformed (FT) AC voltammetry was used at high frequency to study the electrode kinetics of tetrathiafulvalene (TTF), its radical cation TTF.+ and that of the dication TTF2+ in acetonitrile (0.1 M Bu4NPF6). The two oxidized forms were prepared by quantitative bulk electrolysis of TTF under dry-box conditions. A high frequency of 233 Hz was used at glassy carbon (GC) and platinum (Pt) macro disk electrodes to enhance the kinetic sensitivity and hence upper limit of the measurable heterogeneous charge transfer rate constant (k0). Difficulties associated with the use of high frequencies at macro disk electrodes are discussed. Comparison of experimental data with simulations is used to extract k0 and other parameters for each of the TTF0/.+ and TTF.+/2+ processes from both reduction and oxidation perspectives. k0 values for TTF0/.+and TTF.+/0 processes are ≥1.0 cm s−1 and consequently regarded as reversible under the AC conditions used. However, the significantly slower quasi-reversible behaviour observed for the TTF.+/2+ redox couple, with k0 being 0.3±0.05 cm s−1, can be precisely estimated.