Some 20 rate constants of highly exergonic thermal electron-transfer reactions between reduced metal-polypyridine complexes and radical cations of aromatic molecules have been measured by laser and flash photolysis techniques. The rate constant values remain at diffusion-controlled levels up to free energy changes of -58 kcal/mol. Such exergonicity values are more than twice the value at which the classical Marcus theory, under the most favorable assumption, predicts the onset of the inverted behavior to occur. In the reactions studied, the energetics of the products (which are molecules in their standard oxidation states) is well-known, and the formation of electronically excited states can be very safely ruled out. Among the possible reasons for the failure to observe the inverted behavior, quantum effects (nuclear tunneling) are believed to play the major role in these systems. Measurements of the yields of formation of the reactants in the flash photolysis experiments also point toward the lack of any inverted behavior in these reactions. © 1984 American Chemical Society.

Experimental investigation of highly exergonic outer-sphere electron-transfer reactions

INDELLI, Maria Teresa;SCANDOLA, Franco
1984

Abstract

Some 20 rate constants of highly exergonic thermal electron-transfer reactions between reduced metal-polypyridine complexes and radical cations of aromatic molecules have been measured by laser and flash photolysis techniques. The rate constant values remain at diffusion-controlled levels up to free energy changes of -58 kcal/mol. Such exergonicity values are more than twice the value at which the classical Marcus theory, under the most favorable assumption, predicts the onset of the inverted behavior to occur. In the reactions studied, the energetics of the products (which are molecules in their standard oxidation states) is well-known, and the formation of electronically excited states can be very safely ruled out. Among the possible reasons for the failure to observe the inverted behavior, quantum effects (nuclear tunneling) are believed to play the major role in these systems. Measurements of the yields of formation of the reactants in the flash photolysis experiments also point toward the lack of any inverted behavior in these reactions. © 1984 American Chemical Society.
1984
Indelli, Maria Teresa; R., Ballardini; Scandola, Franco
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11392/1683890
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