Ferrocene-ferricinium coupl solvents

The caesium assumption is popular with electrochemists and gives results comparable with the ferrocene-ferricinium assumption (ii) at least for solutions in water, formamide, methanol, and acetonitrile (Kolthoff, 1964 Strehlow, 1952 Koepp et al., 1960). However, we favour the tetraphenylarsonium-tetraphenylboride assumption of Grunwald et al. (1960) because it makes a more satisfactory allowance for size effects, such as making and breaking of solvent structure, while still preserving the attractive features, as to electrostatic solvation, possessed by the ferrocene-ferricinium couple and the caesium cation. 

A three-electrode cell with one or two compartments. If the potentiostatic or potentiodynamic method is used, a reference electrode is necessary. The reference electrode may be simply a silver wire, pseudoreference. Its potential is not particularly stable and it should be standardized before or after every use by measuring a cyclic voltammogram of ferrocene. The redox potential of the ferrocene-ferricinium couple is well known in all common solvents and hence this couple is generally used as a potential standard. 

Electrosynthesis of the polythiopene was realized on an indium-tin-oxide (ITO) electrode (glass blade covered with an indium-doped tin-oxide film). Before conducting the experiment, each electrode was cleaned by ultrasonication for 10 min in different solvents (acetone, dichloromethane, ether). Electrochemical experiments were performed in a three-compartment cell. The working electrode was the ITO electrode, the counter electrode was a Pt wke, and the reference electrode was an aqueous-saturated calomel electrode (E°/SCE = E°/NHE — 0.2412 V) with a salt bridge containing the supporting electrode. The SCE electrode was checked against the ferrocene/ferricinium couple (E = -1-0.405 V/SCE) before and after each experiment. 

The ferrocene/ferricinium ion electrode. For nonaqueous electrochemistry, IUPAC recommends47 the use of the ferrocene/ferricinium ion [Fen(Cp)2/ Fen(Cp)2 , HCp = cyclopentadiene] couple as an internal standard. The couple has been chosen because its potential is largely independent of the solvent (E° = +0.40 V vs. NHE in water 3 and +0.69, +0.72, +0.76, and +0.68 V vs. NHE in MeCN, DMF, py, and Me2SO, respectively).48 The ferricinium ion is unstable in some organic solvents because of decomposition.49,50 Recently the use of bis(pentamethylcyclopentadienyl) iron(II) has been proposed to avoid the problem.51 The Fen(Cp)2/Fem(Cp)2 couple cannot be used as an internal standard for some systems due to overlapping waves.52 In these cases other compounds such as tris-(l,10-phenanthroline)iron(II),4 cobalto-... 

In 1980 Singh et al. reported the first example of a photoelectrochemical cell using an RTIL. They employed a chloroaluminate melt based on the A -butylpyridinium cation, denoted as BP, as a solvent and III-V semiconductors, namely n-GaAs [9-12] or n-InP [13], as the photoanode. Ferrocene and ferricinium chloride were used as the redox couple. The chloroaluminate-based RTIL used here was prepared by mixing equimolar amounts of AICI3 and BP-Cl. The viscosity of the RTIL is 21 mPas at 25°C [14]. 

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