One-electron redox potentials

The one electron redox potentials of 1-2 along with those of the appropriate reference compounds are presented in Table I. The redox potentials of both the porphyrins and the quinones are not altered by linking the two molecules. These potentials were used to obtain the exothermicity of the charge separation, and that of the charge recombination, -AG from... 

Steenken, S. and Neta, P., One-electron redox potentials of phenols. Hydroxy and amino-phenols and related compounds of biological interest, J. Phys. Chem., 3661, 1982. 

Fig. 34 Plot of log k versus the one-electron redox potentials E of the POMs (taken from Ref 174).

The experiments were performed under pseudo first order rate conditions. The results are gathered in Table 16, which also gives the standard potential for the first redox system of each POM. Figure 34 shows the plot of logiok as a function of the one-electron redox potentials of the POMs. A straight line is obtained with a slope of 16.4 V h... 

Radical cations can be generated by many chemical oxidizing reagents, including Brpnsted and Lewis acids, the halogens, peroxide anions or radical anions, metal ions or oxides, nitrosonium and dioxygenyl ions, stable aminium radical cations, semiconductor surfaces, and suitable zeolites. In principle, it is possible to choose a reagent with a one-electron redox potential sufficient for oxidation-reduction, and a two-electron potential insufficient for oxidation-reduction of the radical ion. 

The change in free energy (AG) for electron-transfer (ET) reactions is given by an empirical relation (Eq. 11 Ej is the excited-state energy, Eqx and E ed are the one-electron redox potentials of donor and acceptor, respectively, and is a... 

Riefler, R. G., and B. F. Smets, Enzymatic reduction of 2,4,6-dinitrotoluene and related nitroarenes Kinetics linked to one-electron redox potentials , Environ. Sci. Technol, 34, 3900-3906 (2000). 

Figure 4B. Plots of log kc, for the photoinduced electron transfer reactions from [Ru(bpy)3]2+ to organic electron acceptors (Nos. 1-16) in the absence of HC104 and acetophenone derivatives (Nos. 17-21) in the presence of HC104 (0.10 mol dm-3) in MeCN vs. the difference between the one-electron redox potentials of [Ru(bpy)3]2 + and the electron acceptors in the absence of HC104 in MeCN, [42].

Electron donor and acceptor capabilities are enhanced significantly by photoexcitation in comparison with those of the ground states. This is because one-electron redox potentials of excited states are shifted drastically... 

Bahnemann D, Asmus K-D, Willson RL (1983) Phenothiazine radical-cations electron transfer equilibria with iodide ions and the determination of one-electron redox potentials by pulse radiolysis. J Chem Soc Perkin Trans 2 1669-1673... 

Jovanovic SV, Simic MG (1986) One-electron redox potentials of purines and pyrimidines. J Phys Chem 90 974-978... 

Seidel CAM, Schulz A, Sauer MHM (1996) Nucleobase-specific quenching of fluorescent dyes. 1. Nu-cleobase one-electron redox potentials and their correlation with static and dynamic quenching efficiencies. J Phys Chem 100 5541-5553... 

Another important aspect of peroxidase reactions is the relation between the substrate one-electron redox potential and the redox potential of compound I and compound II, since this restricts the number of possible redox partners (see Chap. 4 for a detailed description). Table 6.1 reports the redox potentials of some selected peroxidases as it can be seen, the values span an interval ranging from 1.35 V for reduction of myeloperoxidase (MPO) compound I to 1.0 V for reduction of HRP compound I [13-15]. But the selection of the preferred enzyme for a given radical reaction must consider not only the complementarities in the redox potentials but also the mechanism preferred by the enzyme, since some peroxidases, such as CPO and MPO, and also LPO in some cases, react through a two-electron oxidation mechanism. 

Most phenols have one electron redox potential, which allows their oxidation by compound I and compound II to phenoxide radicals according to the following reactions ... 

As the two one-electron redox potentials involved are close to 1V, many aromatic compounds can be oxidized to a radical cation. This is a common source of free radical production during intoxication with xenobiotics [31]. The large difference in redox potential between the two couples O2/H2O2 and H2O2/H2O provides a thermodynamic driving force for H2O2 dismutation catalyzed by catalase ... 

The sensitization threshold is at half-wave potential -0.50 V of a sensitizer with displacement E1/2 to more positive region the sensitizing properties of nitroazoles are nonlinearly growing (see Table 3.43) [919], The best sensitizing properties are marked on nitroazoles, reduced in the potentials E1/2 range from -0.2 to -0.35 V. A linear dependence has been found out between one-electron redox potentials of nitroimidazoles and - log 1/R37 values (r=0.96, n=6). Parameter R37 characterizes an activity of a drug (37% of DNA X174 population survival) [919],... 

Analyses of the electrochemical data for 2-, 5-, and 4-nitroimidazoles show them to be the weakest oxidants with one-electron redox potentials (E7 ) of only -0.517 V [940], The potentials E7 for 2-nitroimidazoles and 5-nitroimidazoles vary within a range from -0.243 to 0.423 and -0.457 to -0.486 V, respectively (Table 3.47) [940, 941], A linear dependence of one-electron reduction potentials of substituted 2- and 5-nitroimidazoles on the sizes [S] is observed (Table 3.47) [940, 941],... 

Table 3.47 One-electron redox potentials and radiosensitizing properties of nitroimidazoles [941]...

One-electron redox potentials of 2-substituted l-methyl-4-nitroimidazolcs correlate with their antiparasitic activity (Entamoeba histolytica) the activity is increased with decreasing redox potentials [952],... 

Reactions of this type involve the oxidation/reduction of a reactive intermediate for which the one-electron redox potential may not be known (C02 in Eq. 5). Determination of the free energy for formation of the emissive state requires knowledge of the potentials of both ion radicals and the energy of the emitting excited state (Eq. 2). It is, in principle, possible to find approximate values for one-electron potentials of very unstable ion radicals (e.g., the C02 / potential of Eq. 5) by use of a series of chromophores with varying potentials for forming the excited state from the radical ion (varying RUB+/ potentials). 

One can then attempt to relate the free energy of the reaction (or the equilibrium constant or the redox potential) of the one-electron step to the rate of the reaction. Extensive tabulations of one-electron redox potentials have recently become available (e.g., Wardman, 1989). Often it is possible to relate rate constants to free energy parameters (AG , K, pe°) in a series of related redox reactions (e.g., oxidation of ions of transition elements with O2, H2O2, Mn02, etc.) or redox reactions involving organic compounds with var-... 

Most reviewers5 8 now argue that photosynthetic oxygen evolution results from a sequential four-step electron-transfer process in which oxidizing equivalents from chi fl+- are accumulated in a "charge-storing" complex to accomplish the concerted four-electron oxidation of two H2O molecules to one O2 molecule. The photooxidant (chi + ) and reductant (pheo O are one-electron transfer agents, and the matrix is the lipoprotein thylakoid membrane. Hence, evaluation and consideration of the one-electron redox potentials for PS 11 components within a lipoprotein matrix are necessary in order to assess the thermodynamic feasibility of proposed mechanistic sequences. 

Meisel, D., and P. Neta (1975), One-Electron Redox Potentials of Nitro Compounds and Radiosensitizers. Correlation with Spin Densities of Their Radical Anions, J. Am. Chem. Soc. 97, 5198-5203. 

Neta P, Simic MG, and Hoffman MZ, Pulse radiolysis and electron spin resonance studies of nitroaromatic radical anions. Optical absorption spectra, kinetics, and one-electron redox potentials, J. Phys. Chem., 80, 2018, 1976. 

Whereas much of the underlying mechanisms for the effects of radiation on materials were outlined using steady state radiation sources, the advent of pulse radiolysis on the heels of flash photolysis opened a window into direct observation of the intermediates. One of the early discoveries utilizing pulse radiolysis was the spectrophotometric detection of the hydrated electron by Boag and Hart (35,36). Since then thousands of rate constants, absorption spectra, one-electron redox potentials and radical yields have been collected using the pulse radiolysis technique. The Radiation Chemistry Data Center at the University of Notre Dame accumulates this information and posts it (at www.rcdc.nd.edu/) for the scientific community to use. They cover the reactions of the primary radicals of water and many organic radicals and inorganic intermediates. 

Aromatic compounds reversible one-electron redox potentials, 496 Arsenates, tetraphenyl-gravimetry, 534 Arsenic, pentaphenyl-stereochcmisiry, 40 Arsenic tribromide stereochemistry, 36 Arsenic trichloride stereochemistry, 36 Arsenic trifluoride stereochemistry, 36 Arsenic trihalidcs stereochemistry, 36 Arsenic triiodide stereochemistry, 36 Arsine, ethylmethylphenyl-complexes inversion, 199... 

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