Abstract
Estimates of the reaction zone thickness over which electron tunneling can effectively occur for the outer-sphere electrochemical reduction of some Cr(III) complexes are obtained by comparing the observed work-corrected rate constants with unimolecular rate constants for the electroreduction of structurally similar surface-bound Cr(III) reactants. Effective reaction zone thicknesses of ca. 0.1-0.3 and ca. 5 Å are obtained for outer-sphere electron transfer with Cr(III) reactants containing predominantly aquo or ammine ligands, respectively. This indicates that the former reactions are marginally nonadiabatic whereas the latter are decidedly adiabatic at their respective planes of closest approach. These findings are compatible with the greater reactant-electrode separation distances previously noted for Cr(III) aquo relative to ammine complexes resulting from the more extensive hydration sheath surrounding the former reactants. Comparisons with recent calculates performed for some outer-sphere homogeneous reactions suggest that efficient electron tunneling takes place over roughly comparable distances at metal-electrolyte interfaces and in bulk solution.
| Original language | English |
|---|---|
| Pages (from-to) | 1463-1467 |
| Number of pages | 5 |
| Journal | Journal of Physical Chemistry |
| Volume | 88 |
| Issue number | 8 |
| Publication status | Published - 1984 |
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- Physical and Theoretical Chemistry
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Experimental estimate of the electron-tunneling distance for some outer-sphere electrochemical reactions. / Hupp, Joseph T; Weaver, Michael J.
In: Journal of Physical Chemistry, Vol. 88, No. 8, 1984, p. 1463-1467.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Experimental estimate of the electron-tunneling distance for some outer-sphere electrochemical reactions
AU - Hupp, Joseph T
AU - Weaver, Michael J.
PY - 1984
Y1 - 1984
N2 - Estimates of the reaction zone thickness over which electron tunneling can effectively occur for the outer-sphere electrochemical reduction of some Cr(III) complexes are obtained by comparing the observed work-corrected rate constants with unimolecular rate constants for the electroreduction of structurally similar surface-bound Cr(III) reactants. Effective reaction zone thicknesses of ca. 0.1-0.3 and ca. 5 Å are obtained for outer-sphere electron transfer with Cr(III) reactants containing predominantly aquo or ammine ligands, respectively. This indicates that the former reactions are marginally nonadiabatic whereas the latter are decidedly adiabatic at their respective planes of closest approach. These findings are compatible with the greater reactant-electrode separation distances previously noted for Cr(III) aquo relative to ammine complexes resulting from the more extensive hydration sheath surrounding the former reactants. Comparisons with recent calculates performed for some outer-sphere homogeneous reactions suggest that efficient electron tunneling takes place over roughly comparable distances at metal-electrolyte interfaces and in bulk solution.
AB - Estimates of the reaction zone thickness over which electron tunneling can effectively occur for the outer-sphere electrochemical reduction of some Cr(III) complexes are obtained by comparing the observed work-corrected rate constants with unimolecular rate constants for the electroreduction of structurally similar surface-bound Cr(III) reactants. Effective reaction zone thicknesses of ca. 0.1-0.3 and ca. 5 Å are obtained for outer-sphere electron transfer with Cr(III) reactants containing predominantly aquo or ammine ligands, respectively. This indicates that the former reactions are marginally nonadiabatic whereas the latter are decidedly adiabatic at their respective planes of closest approach. These findings are compatible with the greater reactant-electrode separation distances previously noted for Cr(III) aquo relative to ammine complexes resulting from the more extensive hydration sheath surrounding the former reactants. Comparisons with recent calculates performed for some outer-sphere homogeneous reactions suggest that efficient electron tunneling takes place over roughly comparable distances at metal-electrolyte interfaces and in bulk solution.
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M3 - Article
VL - 88
SP - 1463
EP - 1467
JO - Journal of Physical Chemistry
JF - Journal of Physical Chemistry
SN - 0022-3654
IS - 8
ER -