Acetonitrile electron transfer rate

Fig. 5. Plot of apparent electron self exchange rate constants kf P, derived from polymer De values for films containing the indicated metals, mixed valent states, and ligands, all in acetonitrile, using Equation 2, vs. literature heterogeneous electron transfer rate constants k° for the corresponding monomers in nitrile solvents. See Ref. 6 for details. (Reproduced from Ref. 6. Copyright 1987 American Chemical Society.)...

After all, the released cation-radical reacts with oxygen according to Scheme 5.23. This reaction was performed in acetonitrile, a solvent of high polarity. For solvents of moderate polarities, the addition of salts, that is, electrolytes increases their polarity (Thompson and Simon 1993). With increased solvent polarity, the electron-transfer rates also increase (Scheme 5.24). 

Fig. 4. Back electron transfer rates in photogenerated radical ion pairs in acetonitrile. In all cases cyanoanthracenes served as electron acceptors in their excited states, (a) Methylated benzene derivatives [60b] as donors (one-ring compounds), V = 11.5 cm"1, As = 1.63 eV. (b) Methylated biphenyls or naphthalenes [60b] as donors (two-ring compounds), V = 8.5 cm-1, /, = 1.48 eV. (c) Methylated phenanthrenes [60b] as donors (three-ring compounds) V = 8.0 cm-1, Xs = 1.40 eV. (dl Diphenylbutadienes [61] as donors, V = 8 cm-, X, = 1.55 eV. In all cases X, = 0.25 eV and V= 1500 cm-1...

Fig. 5. Back electron transfer rates in photogenerated radical ion pairs in acetonitrile (a) 9,10-Dicyanoanthracene in its excited state served as the acceptor. Aryl, alkyl, methoxy and amino benzene derivatives as well as aliphatic amines served as donors [62] (V = 23 cm-1, 2, = 0.97 eV, Aj = 0.64 eV). (b) Perylene, pyrene, benzperylene, and aromatic amines served as donors. Tetracyanoethylene (TCNE), pyromellitic dianhydride (PMDA), phthalic anhydride (PA), maleic anhydride, pyrene and perylene served as electron acceptors [63], Various combinations of donors or acceptors were excited (V = 20 cm , As = 1.45 eV, A, = 0.07 eV). The parabolas drawn are different from those offered in the original analysis. The parameters that were used were selected to emphasize the similarity to Fig. 4 (in all cases v = 1500 cm-1)...

In contrast to the cobalt-based system, small amounts of H2 and no CO are produced when nickel cyclam or other saturated 14-membered tetraazamacrocycles (L) in Figure 3 are used to replace the cobalt complex in the above system [22]. Flash photolysis studies indicate that the electron-transfer rate constant (kn) for the reaction of the />-terphenyl radical anion with Nil (cyclam)2 is 4.3 x 10 M s. However, when CO2 is added to the solution, the decay of the TP anion becomes slower Flash photolysis studies of the acetonitrile solutions... 

Mac, M., Wirz, J., Deriving Intrinsic Electron transfer Rates from Nonlinear Stern Volmer Dependencies for Fluorescence Quenching of Aromatic Molecules by Inorganic Anions in Acetonitrile, Chem. Phys. Lett. 1993, 211, 20 26. 

First-order electron-transfer rate constant k > in acetonitrile as a function of the donor-acceptor distance R for a variety of the free energy change A O. 

The electrochemical oxidation of ferrocene and amphiphilic ferrocenes, 2- and 5-(ferrocenylcarboxy)dodecyltrimethylammonium nitrates (2-Fc and 5-Fc, respectively), were investigated in a bicontinuous microemulsion containing CTAC, -tetradecane, pentanol, and water [83]. The electron transfer rates for ferrocene, 2-Fc, and 5-Fc in microemulsions were an order of magnitude slower than in acetonitrile, possibly due to partial inhibition by microemulsion components adsorbed on the electrode [5,6]. The rates of electron transfer of 2-Fc and 5-Fc were only two-fold smaller than that of ferrocene, in contrast to 10-fold (2-Fc) and 100-fold (5-Fc) smaller in CTAB micelles [84]. These results indicate an increased disorder and mobility at the electrode/fluid interface in the CTAC microemulsion compared to CTAB micellar system [83]. 

Figure 9.17 Distance-dependence of in some donor-acceptor molecules. Plots of log( et) edge-to-edge distances in a variety of linked donor-acceptor systems, (a) Forward(D) and reverse (x) electron-transfer rate constants for zinc porphyrin-anthraquinone compounds in butyronitrile. (b) Forward ( ) and reverse (x) electron-transfer rate constants for dimethoxynaphthalene-dicyanoethylene compounds in benzene, compared with the forward rate constants for three anthracene-dimethylaniline systems (V) and four analogous pyrene-dimethylaniline molecules (-I-), all in acetonitrile. From J.S. Connolly and J.R. Bolton, in Ref. [21,e, p. 322].

Aromatic diazo compounds can be reduced in water via a radical process (Scheme 11.5).108 The reduction mechanism of arenediazo-nium salts by hydroquinone was studied in detail.109 Arenediazonium tetrafluoroborate salts undergo facile electron-transfer reactions with hydroquinone in aqueous phosphate-buffered solution containing the hydrogen donor solvent acetonitrile. Reaction rates are first order in a... 

The reductive cleavage of iodobenzene and 3-methyliodobenzene was studied by cyclic voltammetry in both DMF and acetonitrile at 21 and 56 °C at different scan rates and has shown that there is a transition between stepwise and concerted mechanisms at lower scan rates. 1-Iodonaphthalene undergoes a stepwise reductive cleavage with mixed kinetic control by electron transfer and follow-up bond breaking, whatever the scan rate. ... 

Temperature and pressure effects on rate constants for [Fe(phen)3] +/[Fe(phen)3] + electron transfer in water and in acetonitrile have yielded activation parameters AF was discussed in relation to possible nonadiabaticity and solvation contributions. Solvation effects on AF° for [Fe(diimine)3] " " " " half-cells, related diimine/cyanide ternary systems (diimine = phen, bipy), and also [Fe(CN)6] and Fe aq/Fe aq, have been assessed. Initial state-transition state analyses for base hydrolysis and for peroxodisulfate oxidation for [Fe(diimine)3] +, [Fe(tsb)2] ", [Fe(cage)] " " in DMSO-water mixtures suggest that base hydrolysis is generally controlled by hydroxide (de)hydration, but that in peroxodisulfate oxidation solvation changes for both reactants are significant in determining the overall reactivity pattern. ... 

The fates of the radical ion pairs produced upon electron transfer depends on the nature of their production. As already mentioned, the Bp DMA" com formed from irradiation of the ground-state CT complex. Bp - DMA, is suggested by Mataga and co-workers [24] to decay only by febet, on a timescale of 85 ps. Diffusional separation to solvent separated radical ion pairs or proton transfer within Bp -DMA com are not kinetically competitive. The triplet CRIP Bp -I- DMA" ip has two decay pathways that occur on the picosecond timescale. The first process is proton transfer, fept, to generate a triplet radical pair, BpH-l- DMA ] (Scheme 2.3). In acetonitrile, this occurs with a rate constant of fept of 1.3 x 10 s [43]. The second process leading to the decay of the CRIP is diffusional separation to the SSRIP, kips, which occurs with a rate constant of 5 x 10 s (Scheme 2.3) [43]. Thus the efficiency of the... 

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