Noncontinuum solvent effects upon the intrinsic free-energy barrier for electron-transfer reactions

Joseph T Hupp, Michael J. Weaver

Research output: Contribution to journalArticle

49 Citations (Scopus)

Abstract

A phenomenological electrochemical approach is outlined by which "noncontinuum" contributions to the outer-shell intrinsic barrier to electron transfer, ΔG*os, resulting from specific reactant-solvent interactions can be estimated from the measured dependence of the formal potential upon the molecular and structural properties of the solvent. A simplified derivation, based on electrochemical half-reactions, of the conventional dielectric continuum expression is given in order to clarify the physical origins of the outer-shell intrinsic barrier and to identify likely additional noncontinuum components. Numerical calculations for ammine and other redox couples involving specific ligand-solvent interactions indicate that the noncontinuum contributions to ΔG*os for both homogeneous and electrochemical exchange reactions can be surprisingly small (typically ≲1-2 kcal mol-1) even when the thermodynamics of ion solvation are in severe disagreement with the dielectric continuum (Born) predictions. An additional noncontinuum component associated with vibrational distortions of outer-shell solvent may be significant for multicharged aquo complexes and other reactants engaging in strong ligand-solvent hydrogen bonding.

Original languageEnglish
Pages (from-to)1601-1608
Number of pages8
JournalJournal of Physical Chemistry
Volume89
Issue number9
Publication statusPublished - 1985

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Energy barriers
Free energy
electron transfer
free energy
Electrons
Ligands
ammines
continuums
ligands
molecular properties
Solvation
solvation
Structural properties
Hydrogen bonds
derivation
interactions
Thermodynamics
Ions
thermodynamics
hydrogen

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Noncontinuum solvent effects upon the intrinsic free-energy barrier for electron-transfer reactions. / Hupp, Joseph T; Weaver, Michael J.

In: Journal of Physical Chemistry, Vol. 89, No. 9, 1985, p. 1601-1608.

Research output: Contribution to journalArticle

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