Single oxides

When the host is a mixed oxide, the incorporation of the chromophore is best achieved during high temperature formation from single oxides ... 

When the host is a single oxide, incorporation is best achieved during a high temperature phase transition of the host lattice such as when Ti02 goes from anatase to mtile, or during formation from carbonates or other salts. 

Notes. In the case of a single oxide (or hydroxide) existing in different allotropic states, indicated by the letters a, b, c, d, etc. the oxides are arranged in descending order of stability, i.e. in ascending order of standard chemical potentials (expressed for an identical chemical formula). 

Polynuclear transition metal cyanides such as the well-known Prussian blue and its analogues with osmium and ruthenium have been intensely studied Prussian blue films on electrodes are formed as microcrystalline materials by the electrochemical reduction of FeFe(CN)g in aqueous solutionThey show two reversible redox reactions, and due to the intense color of the single oxidation states, they appear to be candidates for electrochromic displays Ion exchange properties in the reduced state are limited to certain ions having similar ionic radii. Thus, the reversible... 

The electrosynthesis of 4-methoxybenzaldehyde (anisaldehyde) from 4-methoxy-toluene by means of direct anodic oxidation is performed on an industrial scale [69]. Via an intermediate methyl ether derivative, the corresponding diacetal is obtained, which can be hydrolyzed to the target product. The different types of products - ether, diacetal, aldehyde - correspond to three distinct single oxidation steps. 

The first report of the SERS spectrum of a species adsorbed at the electrode/ electrolyte interface was by Fleischman et al (1974) and concerned pyridine on silver. The Raman spectrum of the adsorbed pyridine was only observed after repeated oxidation/reduction cycles of the silver electrode, which resulted in a roughened surface. Initially, it was thought that the 106-fold enhancement in emission intensity arose as a result of the substantially increased surface area of the Ag and thus depended simply on the amount of adsorbate. However, Jeanmarie and Van Duync (1977) and Albrecht and Creighton (1977), independently reported that only a single oxidation/reduction cycle was required to produce an intense Raman spectrum and calculations showed that the increase in surface area could not possibly be sufficient to give the observed enhancement. 

The same analysis will hold for any metal in contact with its single oxide. In order to determine the oxygen partial pressure over the pair, it is only necessary to know the value of the free energy of the reaction at the temperature required and insert the value into the following equation ... 

Any positively charged chemical species can be considered a cation or as being in a cationic form. Some will be present as relatively simple, single-oxidation-state cations such as sodium (Na+). Others may be more complex in that they may have several oxidation states such as iron, in either the Fe2+ or Fe3+ states. Cations may also have oxygens or hydroxy groups associated with them, such as FeO+. 

As illustrated in Figure 19, the compound displays in CH2C12 solution a single oxidation process (the small return peak marked by an asterisk is due to a slight adsorption of the oxidation product at the electrode surface). Controlled potential electrolysis shows that such an oxidation is chemically reversible and involves a two-electron step.28... 

Ferrocene-based Linear Polymers. The first derivative that was studied from the electrochemical point of view was polyvinylferrocene (PVF). As illustrated in Figure 25, it displays a single oxidation process, which in some solvents is affected by problems of adsorption of the oxidation product (though not of the ideal Langmuir isotherm type discussed in Chapter 2, Section 1.6). 

It is important to note that the appearance of a single oxidation process for PVF indicates that there is no interaction between the ferrocene subunits in the polymer chain, which means that the carbon chain creates a barrier blocking the electronic communication between the ferrocenyl groups. 

As seen, it affords a single oxidation process the cyclic voltammetric profile of which is very close to that expected for the mechanism ... 

Both the complexes display, in dichloromethane solution, a single oxidation process which involves four ( ° = + 0.40 V, vj. SCE) and eight (jE °/ = -1- 0.44 V, vj. SCE) electrons, respectively. This means that no electronic communication exists among the ferrocenyl units. 

It exhibits a single oxidation process (Ea = + 0.59 V, vs. SCE) affected by some adsorption problems. These adsorption phenomena, which typically affect the electrochemical response of these derivatives, sometimes make it difficult to ascertain by controlled potential coulometry the effective number of electrons involved in the oxidation step. In this case, the (approximate) number of electrons involved per molecule of dendrimer, nd, can be roughly calculated by comparing the cyclic voltammetric responses of the dendrimer with that of the ferrocene monomer using the following empirical equation.27,40... 

As seen, these complexes also exhibit a single oxidation process involving a number of electrons equal to the number of ferrocene units. 

The complex undergoes in dichloromethane solution a partially reversible single oxidation (E° = —0.25 V, vs. SCE), assigned as a one-electron process. This result would support the access to the corresponding mixed-valent Fe(II)Fe(III) species, the partial reversibility of the process having been attributed to deprotonation of the -hydroxo group.35... 

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