The new theory of electron transfer. Thermodynamic potential profiles in the inverted and superverted regions |
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Authors: | Stephen Fletcher |
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Institution: | (1) Department of Chemistry, Loughborough University, Ashby Road, Loughborough, Leicestershire, LE11 3TU, UK |
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Abstract: | In a previous paper (S Fletcher, J Solid State Electrochem 11:965, 2007) a non-Marcus theory of electron transfer was developed, with results applicable to the normal region of thermodynamic
driving forces. In the present paper, the theory is extended to highly exergonic reactions (the inverted region) and to highly
endergonic reactions (the superverted region). The results are presented mathematically and in the form of Gibbs energy profiles
plotted against a charge fluctuation reaction coordinate. The new theory utilizes the concept of donor and acceptor “supermolecules,”
which consist of conventional donor and acceptor species plus their associated ionic atmospheres. The key findings are as
follows. (1) In the inverted region, donor supermolecules are positively charged both before and after the electron transfer
event. (2) In the normal region, donor supermolecules change polarity from negative to positive during the electron transfer
event. (3) In the superverted region, the donor supermolecule is negatively charged both before and after the electron transfer
event. This overall pattern of events makes it possible for polar solvents to catalyse electron transfer in the inverted and
superverted regions. Because this new effect is predicted only by the present theory and not by the Marcus theory, it provides
a clear means of distinguishing between them. |
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Keywords: | Marcus theory Electron transfer theory Reorganization energy Inverted region Superverted region Exergonic reactions |
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