Formal reduction potential,

Fig. 5a. Standard (or formal) reduction potentials of actinium and the actinide ions in acidic (pH 0) and basic (pH 14) aqueous solutions (values are in volts...

The chemistry of plutonium ions in solution has been thoroughly studied and reviewed (30,94—97). Thermodynamic properties of aqueous ions of Pu are given in Table 8 and in the Uterature (64—66). The formal reduction potentials in aqueous solutions of 1 Af HCIO or KOH at 25°C maybe summarized as follows (66,86,98—100) ... 

Table 10 Anodic shifts (mV) in the formal reduction potentials of [50]—[53] upon addition of alkali metal cations.

Table 3. Formal reduction potentials (in volts) of uranium, neptunium, plutonium and americium for 1 M perchloric add solutions at 25 °C. (F. A. Cotton and G. Wilkinson Advanced Inorganic Chemistry. Interscience Publishers 1972)...

The chemistry of the transition metals including chromium(III) with these ligands has been the subject of a recent and extensive review,788 with references to the early literature. The close relationship between the catechol (180), semiquinone (181) and quinone (182) complexes may be appreciated by considering the redox equation below (equation 44). 789 The formal reduction potentials for the chromium(III) complexes (183-186 equation 45) are +0.03, -0.47 and -0.89 V (vs. SCE in acetonitrile) respectively. 

The formal reduction potential of silver ion in DMF was found to be +0.579 0.004 V vs. SCE. The values of the stability constants of the DMF complexes of silver(I) in various solvents are given in Table 38. It was observed that the complexes were most stable in nitroethane.274... 

The solution chemistry of uranium is that of the +4 and +6 oxidation states, that is, U4+ and U02+. The formal reduction potential of uranium in aqueous solution (i.e., 1 M HC104) is... 

Table 8.1 presents estimates of the differential formation energies for Af—H(s) bonds [A(—AGbF)J at various metal electrodes.3 On the basis of these and Eq. (8.7), approximate formal reduction potentials [ ,m h3o+/w-h(s)] have been estimated for the reduction of H30+ (unit activity) at die several metal electrodes (Table 8.1). In our view direct evaluations of A(—AGBF)M H(S) via electrochemistiy will provide useful insights to metal-hydrogen bonds and metal-catalyzed hydrogenations.

TABLE 8.1 Estimates of the Differential Formation Energies for M— H(s) Bonds [A(-AGBF>] at Metal-Electrode Surfaces [M(s>], and Approximate Formal Reduction Potentials for H30+ at Metal Electrodes (E Hjo+/a/-h)... 

TABLE 9.4 Formal Reduction Potentials for Dioxygen Species in Acetonitrile [02 at 1 atm (8.1 mM>]... 

B. Formal Reduction Potentials for the 02/02 couple (molar concentrations for 02 and 02)... 

Table 20-4 Formal Reduction Potentials (V) of the Actinides for 1 M Perchloric Acid Solutions at 25°C (brackets indicate estimate)...

The formal reduction potentials of Np, Pu, and Am were given in Table 20-5 and information on the ions in Table 20-6. Solutions of the IV to VI oxidation states undergo spontaneous reduction because of their own a radiation. For Np (like U), the potentials of the four oxidation states are separated, but unlike the chemistry of U, the Np02 ion is comparatively stable. For Pu, however, the potentials are close and at 25°C in 1 M HC104 we have... 

Table 2 Formal reduction potentials for dioxygen species in acetonitrile ...

Sensitization of electrodes to light relies on the fact that an excited state is simultaneously a stronger oxidant and a stronger reductant than is the ground state. Knowledge of the sensitizer s formal reduction potentials relative to the energy levels of the conductive substrate allows a priori determination of the direction of current flow and the sensitization mechanism. It is therefore of considerable interest to quantify the energetics of the sensitizer and the electrode with respect to one another. This can be accomplished, at least in principle, by spectroscopic and/or electrochemical measurements as described below. 

The formal reduction potentials, E°, for a sensitizer, S, that are most relevant to dye sensitization correspond to the ground, reduced and excited states. The first two can be directly measured by electrochemical techniques, such as cyclic voltammetry, and often in situ at the sensitized electrode of interest [7]. The excited state reduc-... 

Sensitization and interfacial electron transfer mechanisms have been described by Gerischer [4-6]. A basic assumption is that electron transfer, like light absorption, occurs under the restriction of the Franck-Condon principle. The time-scale for interfacial electron transfer is much shorter than that for nuclear motion. This means that the energy terms for electron transfer are different from the thermodynamic formal reduction potentials described above. Gerischer considered the appropriate energy levels and derived a distribution of energy levels when the sensi-... 

There is still only the early direct measurement of the formal reduction potential for U + -l-e"- U +,-0.63lV (Sa). Standard values are less accurate, because of uncertainties in the necessary activity corrections or extrapolation values of -0.607 and -0.596 V (S6) have been estimated but a larger value of -0.52 V has been proposed as more compatible with data on the enthalpies of formation of the hydrated... 

It is usually difficult to determine or impose activities, since activation coefficients are nearly always unknown for the redox systems investigated in organic or organometallic chemistry. Thus formal reduction potentials E° are measured, when feasible, rather than... 

The influence of pH on the formal reduction potential was also examined using the spectroelectrochemical technique. The 1/2 value for MHpx at pH... 

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