Electron transfer classical Marcus theory

The higher rate of the reverse electron transfer in the dimer radical cations than in the monomer radicals was explained by classical Marcus theory as follows [52,53]. The -AG° values for the reverse electron transfer from NS and DCS to TPB were estimated as 1.69 and 1.61 eV from the redox potentials, respectively. The reduction potential of the dimer radical cation should be less negative by 0.65 and 0.59 V than that of the radical monomer radicals due to the stabilization energy. The -AG° values for the reverse electron transfer from the dimer radical cation to TPB were thus estimated to be 1.04 and 1.02 eV for (NS+ -NS ) and (DCS+ -DCS ), respectively [68],... 

The total reorganization energy >. in classical Marcus theory was estimated by the method described below. A plot of the maximum of the IPCT band in solution (T op) against the driving force of electron transfer within the contact... 

To fully understand the relaxation pathways for photoinduced charge-transfer reactions in solutions we need to take solvent effects into account. For that reason it is necessary to recall some basic principles of the classical Marcus Theory for electron-transfer reactions in solution. 

Thus, classical Marcus theory predicts an electron transfer rate that has a Gaussian dependence on the free energy of the reaction (Marcus, 1956 Marcus and Sutin, 1985). 

The self-exchange electron-transfer (SEET) process, in which a radical is trapped by the parent molecule, has been studied using the intersecting-state model (ISM). Absolute rate constants of SEET for a number organic molecules from ISM show a significant improvement over classical Marcus theory in the ability to predict experimental SEET values. A combination of Marcus theory and the Rips and Jortner approach was apphed to the estimation of the amount of charge transferred in the intramolecular ET reactions of isodisubstituted aromatic compounds. ... 

We now turn to the hierarchy of electron-transfer rate theories that have developed since the 1950s, starting with classical Marcus theory of homogeneous reactions and the development of eq. 4.4. In later sections we shall consider theories of nonadiabatic ET, which allow the identification and evaluation of the prefactor A in eq. 4.4, and also electrochemical ET, which differs from homogeneous reactions in that an electronic conductor is one of the reactants . 

In classical Marcus theory (see below), the parameters that determine the rate of an electron transfer process between a donor and an acceptor are the... 

Figure 9.6 Pressure-effect on rates of some self-exchange electron-transfer reactions between metal ions comparison of observed volumes of activation with values calculated from classical Marcus theory for adiabatic reactions. The plot shows calculated and observed AP values (cm mol ) at mid-range of pressure (100 MPa, except 70 MPa for Fe(H20)g ) for adiabatic (filled symbols) and nonadiabatic (open circles) self-exchange in couples with rigid ligands. Solvents (o, ) water ( ) CD3CN (A) (CD3)2CO (V) CD3OD. Key (A,B) (C,D) Cu(dmp)2 (E-G) Ru(hfac)j (H) Fe(C5H5)2 (I-K) Mn(CN-t-Bu)g ...

One of the most exciting developments in the field of electron transfer has been the experimental verification of the classical Marcus theory [326,327], which predicts a decrease in the rate constant for the electron transfer as the exothermicity of the electron fransferring process increases. As it turns out, this so-called Marcus inverted region occurs frequently for photo-... 

Most of the redox proteins have their active centre deeply buried inside the protein matrix which slows down or sometimes insulates the transfer of electrons from protein to the electrode. As per the classical Marcus theory for the monolayer redox couple [Eq. (1)] [16, 43, 44], A et decreases exponentially with the distance of electron transfer, d, where is the electron transfer rate constant at the distance of closest contact do. ... 

Figure 2.1 (Plate 2.1) shows a classification of the processes that we consider they aU involve interaction of the reactants both with the solvent and with the metal electrode. In simple outer sphere electron transfer, the reactant is separated from the electrode by at least one layer of solvent hence, the interaction with the metal is comparatively weak. This is the realm of the classical theories of Marcus [1956], Hush [1958], Levich [1970], and German and Dogonadze [1974]. Outer sphere transfer can also involve the breaking of a bond (Fig. 2. lb), although the reactant is not in direct contact with the metal. In inner sphere processes (Fig. 2. Ic, d) the reactant is in contact with the electrode depending on the electronic structure of the system, the electronic interaction can be weak or strong. Naturally, catalysis involves a strong...

A well defined theory of chemical reactions is required before analyzing solvent effects on this special type of solute. The transition state theory has had an enormous influence in the development of modern chemistry [32-37]. Quantum mechanical theories that go beyond the classical statistical mechanics theory of absolute rate have been developed by several authors [36,38,39], However, there are still compelling motivations to formulate an alternate approach to the quantum theory that goes beyond a theory of reaction rates. In this paper, a particular theory of chemical reactions is elaborated. In this theoretical scheme, solvent effects at the thermodynamic and quantum mechanical level can be treated with a fair degree of generality. The theory can be related to modern versions of the Marcus theory of electron transfer [19,40,41] but there is no... 

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