Ground State Electron Transfer

In total, the situation is less favorable in terms of quantum yields than in the preceding case. Indeed, even if the cleavage rate constant is large enough to overcome back electron transfer from the ion pair (kc k act), the maximal value of the quantum yield is 1/(1 + P), which would reach unity only in the unlikely case where the ground-state electron transfer was entirely non-adiabatic (H = 0). 

The title system in AN forms a homogeneous solution. The generation of NO cation takes place. As known, NO is a remarkable, diverse reagent not only for nitrosation and nitration but also for oxidation. Kochi et al. (1973) christened a new general mechanism oxidative aromatic substitution to describe aromatic snbstitntion reactions (Kochi 1990, Bosch and Kochi 1994). This mechanism incorporates ground-state electron transfer before the substitution step (see also Skokov and Wheeler 1999). 

The reader is also referred to the innovative nonphotochemical electron transfer studies of Weaver et al. [147], These authors have been exploring dynamical solvent effects on ground state self-exchange kinetics for or-ganometallic compounds. This work has explored many aspects of solvent control on intermediate barrier electron transfer reactions, including the effect on a distribution of solvation times. The experimental C(t) data on various solvents have been incorporated into the theoretical modeling of the ground state electron transfer reactions studied by Weaver et al. [147]. 

The possibility of a thermally activated electron transfer from an anion to an acceptor is not always excluded. As explained by Bordwell [106], this will of course depend on the oxidation potential of the anion or on its related basicity and this author has shown that the electron transfer reactivity of carbanions rapidly decreases with a decrease of basicity. It is thus possible that among the dark SRN1 reactions some of them are activated by an initial ground state electron transfer from the anion to the accepting substrate. 

With a donor molecule of low ionization energy and an acceptor of high electron affinity, electron transfer may occur even in the ground state of the complex. When the differences in electron affinity are not pronounced, a structure without bond predominates in the ground state. Electron transfer can be considerably boosted by excitation, by a photon for example. A strong polarization of the donor-acceptor complex occurs [292], leading to its dissociation to radical ions in a solvent of suitable polarity. When a convenient monomer (e. g. A-vinylcarbazole [293], styrene [294], a-methylsty-rene [295], etc.) acts as donor, it can be polymerized by the generated radical ions. 

Potential Energy Surfaces for Ground-State Electron Transfer, Relation to Photochemistry Nonadiabatic Chemistry... 

B. Ground State Electron Transfer Reactions by Pulse Radiolysis... 

In both cases the electron transfer process took place on a sub millisecond time scale. Removal of the voltage resulted in rapid return to the starting state. This is the first time that reverse electron transfer has been activated by voltages applied directly from an external electric source. This demonstration shows the feasibility of electric field induced reverse electron transfer, and holds promise as an unusually flexible alternative for pulse activation of ground state electron transfer. 

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