The electron transfer kinetics of monolayers of CpFeCpC0 2 (CH 2 ) 12 SH and CH 3 (CH 2 ) U SH co-chemisorbed on gold electrodes have been measured in 2:1 (v:v) chloroethane/butyronitrile solvent at temperatures ranging from 125K to 175K with potential steps and cyclic voltammetry. Rate constants, k°, measured using cyclic voltammetry range from 3x10"* to 10" 1 s" 1 over these temperatures; an activation plot of logtkVkbT*] vs. 1/T gave k = 0.89 eV for the reorganization energy for the Cp 2 Fe +/0 reaction and a pre-factor of 6.5xl0 6 eVV 1 . The rate constants were obtained by comparison of experimental AE PEAK values with those of cyclic voltammograms digitally simulated with Marcus-DOS theory. A value of X = 0.76 eV is predicted from dielectric continuum theory.The CpFeCpC0 2 (CH 2 ) 12 SH monolayers are kinetically inhomogeneous (disperse) as shown by non-linear ln[i] vs. time plots in potential step experiments. The kinetic dispersity has adverse effects on determinations of X values from cyclic voltammetric waveshapes and from plots of potential step-derived rate constants, k.^^ against overpotential (??), producing depressed values for X.
Wo ropad cy& vokmmtryfrom 115 to 180 Kln butyronltrlk/ ethyl chlodde solvent for monolayer films of ferrocenetormlnatod alkanothlds chemkorbod on gold electrode rurfacos. The alkyl spacers botweon thlol and ferrocene contalnod 4, 8, and 12 methylene unlts, and the forrocene m0ktko wero diluted wlth alkanethldr of qual chaln length durlng Un-aumnbly of the monomokcular f h onto the gdd electrodw. The -If-a8wnM.d forrocone flbnr dkplay hlghly stabh voltammetry at low temperatures. The magnttudes of tho voltammetrlc peak potontlal soparatlons (AEW) are domlnatod by slow electron-tramfor klnetlcr as opposed to uncompensated rdutlon redstance. Qualltathrely, the electrorctramfor rat08 decrease wlth decreadng temperaturo and wtth Incroadng alkyl chain kngth. The ferrocone alkanethlok retaln m o degree of order and enforcement of a spaclng botween tho electrode and tho ferrocone &ea In splto of their
Anion-exchange experiments performed on electrochemically prepared thin films of polypyrrole/C104~d emonstrate that the anions are not tightly bound to the polymer matrix. Auger electron spectroscopy reveals that C104" can be replaced by a number of different anions. In addition, certain anions will not replace C104" while others will induce only partial replacement. The relevance of entropic and steric factors is discussed in relationship to the exchange process.Polypyrrole was the first, and still is one of the very few, electrochemically prepared conductive polymers. Since it's first electrochemical preparation in 1968,1 polypyrrole has been one of the most extensively studied conductive polymers. Such intense interest arises from several properties which are unique to polypyrrole.2 It combines both good thermal and mechanical properties with air and water stability, although the unoxidized polymer is somewhat susceptible to air oxidation. It is conveniently prepared by the electrochemical oxidation of pyrrole and is obtained as a thin film which adheres to the surface of a platinum electrode.
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