Observed by Cyclic Voltammetry

At potentials lower than the Nernst potential, the deposited Ru species consisted mainly of metallic ruthenium.4 In addition, certain amounts of ruthenium oxides, Ru02 and even Ru03, were detected. This indicates that deposition at lower potentials involved the deposition of metallic Ru, most probably according to the reactions  

With an increase of the potential, the amount of metallic Ru decreases, while the amount of Ru oxides increases, particularly high-valence ruthenium(VI) oxide (Ru03). At the potential higher than 0.6 V, only ruthenium oxides and no metallic Ru are detected byXPS.28 

The formation of RuOH and RuO during electrochemical deposition was ascribed to the presence of Ru0[(H20)4]2+ and formation of RuC 2,ads on the surface and its further evolution according to the reactions  

The electrochemical deposition of Ru at potentials positive to the Nernst potential, when the reconstruction of the underlying Au(l 11) surface had been partly or completely lifted, is illustrated 

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The coordination of redox-active ligands such as 1,2-bis-dithiolates, to the M03Q7 cluster unit, results in oxidation-active complexes in sharp contrast with the electrochemical behavior found for the [Mo3S7Br6] di-anion for which no oxidation process is observed by cyclic voltammetry in acetonitrile within the allowed solvent window [38]. The oxidation potentials are easily accessible and this property can be used to obtain a new family of single-component molecular conductors as will be presented in the next section. Upon reduction, [M03S7 (dithiolate)3] type-11 complexes transform into [Mo3S4(dithiolate)3] type-I dianions, as represented in Eq. (7). 

Recently, Astruc et al. [189] reported novel amido-ferrocene dendrimers (e.g., 91) which were shown to act as supramolecular redox sensors for the recognition of small inorganic ions (Fig. 41). It was further observed that as the den-drimer generation number increased the sensitivity to the guest molecules also increased as observed by cyclic voltammetry experiments. 

Rajca and co-workers have studied star-branched and dendritic high-spin polyradicals which are potential organic magnets. Representative data were obtained for the model tetra-anionic compound 55. Three redox waves were observed by cyclic voltammetry and differential pulse voltammetry for a four-electron process between the potentials of -2.00 and -1.20 V (vs. SCE). Electrochemical experiments with these materials have usually been performed at 200 K. The polyradicals, which are less stable for systems with more unpaired electrons, have been characterized by spectroscopic studies, ESR data, and SQUID magnetometiy. 

An important feature of the rotaxane in Scheme 9.12 is that the translocation of the macrocycle is also achieved by the reduction of the fullerene to its trianion, which is both effected and observed by cyclic voltammetry. In DMSO, the proximity of the macrocycle to the fullerene stabilized substantially the electrogenerated trianion (A i/2 = 46 mV) through n—n interactions. Surprisingly, in THF where the macrocycle is preferentially positioned on the peptide station, a similar behavior was... 

All C60 adducts have low-lying LUMOs that can easily be populated by electrochemical methods. For C60 itself, six reduction couples have been observed by cyclic voltammetry (CV) or square-wave voltammetry (SWV), and as many as four reduction couples have been found for many organometallics (9,84). Most of the studies have been performed in thf or acetonitrile at lower temperatures, which increases the size of the potential window. Table VII lists the half-wave potentials for some metal complexes, and Fig. 7 shows the cyclic voltammogram for [Co(NO)(PPh3)2(i72-C60)]. 

I11 aprotic solvents, the amalgam of R4N is somewhat stable at temperatures well below 0°C, forming a film on the surface of mercury electrode, and its re-oxidation reaction can be observed by cyclic voltammetry. However, at ambient temperatures or in the presence of water and other protic solvents, the amalgam soon decomposes. 

Tetrahydropterins are highly reactive towards oxidation (e.g. 542 — 544) even molecular oxygen can cause hydroxylation. The autoxidation is due to the electron donating groups such as amino and hydroxy, whereas removal of such substituents enhances the stability of the reduced pteridine nucleus tremendously (96CHEC-li(7)70l). The reaction appears to proceed via single electron transfer. The radical cation (543) can be observed by cyclic voltammetry. 

Additionally, substantial effects on the fullerene-centered reduction steps due to cation complexation by the tangential and proximal dibenzo-crown ether were observed by cyclic voltammetry (CV) for ( )-37 [30,55] (Figure 16). The CV was recorded both in the presence of one equivalent of [2.2.2]cryptand and in the presence of ten equivalents of KPF6. The cryptand was added to ensure that the species observed initially was uncomplexed, since peaks corresponding with the Na+ and K+ complexes were observed in the FAB mass spectrum of... 

The mono-cationic species [M(sdt)2]+ (sdt = stilbeneditholate M = Ni, Pd, Pt) has been observed by cyclic voltammetry (CV) at )/2 1.2 V (vs. Fc/Fc+, ferrocene/ferrocenium) (41). The [M(sdt)2]07+ couple is irreversible since the cationic species is highly reactive, which decomposes to give other radical species on the time scale of controlled potential electrolysis even at —40 °C (41). 

As a result, up to four redox waves can be observed by cyclic voltammetry. The separation is proportional to the degree of interaction, and if the interaction is small, some waves can overlap and therefore decrease the number of oxidation waves observed. For instance, three reversible oxidation waves have been observed for 2,2 -bis(tetrathiafulvalenyl) (37) [32]... 

Formation of mono-, di- and tri(cation radicals) was also observed by cyclic voltammetry of compounds 65a and 65b in dichloromethane with 0.1 M TBABF4 (scan rate 50 mV s 1). Both trications were stable in solutions at room temperature for several hours. It is interesting that the tri(cation radical) of 65b is not reactive towards oxygen, as indicated by no loss of ESR signal intensity upon purging its solution with O2. The mono-, di- and tri(cation radicals) of 65b all survive isolation and have been prepared as Ply, salts by NOPF6 oxidation of the parent compound103. 

ROP of hydrocarbon-bridged [2]ferrocenophanes yields polyferrocenylethylenes 88 Ei=E2 = C 2 R = H or Me). Due to the more insulating hydrocarbon bridge in these materials, only slight communication between the iron centers is observed by cyclic voltammetry (redox coupling of A i/2 = 90mV). Nevertheless, cooperative magnetic behavior has been reported in TCNE-oxidized materials at low temperature. 

In a recent report, we described (15) how encapsulating the YBa Cu O- pellets in an epoxy matrix effectively fills the outer pores ana diminishes the problem with large background currents. These electrodes undergo reversible electron transfers with electroactive solutes in a variety of nonaqueous solvents, as observed by cyclic voltammetry. This reversible voltammetry was used as a phenomenological method for estimating the lifetime of such electrodes, in a variety of corrosive media, based on monitoring the voltammetric response as a function of exposure time to corrosive media. 

Electrochemical impedance spectroscopy (EIS) performed at a nominal point evidenced that increases in gas diffusion limitation toward the catalytic site and activation limitation were, most of the time, preponderant to performance loss (Hou, 2007 Song, 2009 Luo, 2010 Park, 2010). However, although an active area decrease is systematically observed by cyclic voltammetry (C V) at active layers, preponderance of diffusion and activation limitations is not clearly identified. According to the literature, degradations related to freezing-thaw cycles can arise from two phenomena ... 

Electrochemical grafting of amine compounds can be easily observed by cyclic voltammetry. Figure 3.56 shows the voltammograms obtained when a GC electrode is immersed in ACN + N-Boc-ethylene diamine solntion [361]. Dnring the first scan... 

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