Mechanistic studies of electron exchange kinetics using ab initio
The rate constant for the aqueous Fe/sup 2 +/-Fe/sup 3 +/ electron exchange reaction is calculated as k/sub ex/= ..integral..4..pi..r/sup 2/g(r)k/sub el/(r)dr, where k/sub el/ is the first-order rate constant for outer-sphere exchange when the Fe complexes are separated by r and g(r) is the pair distribution function for the reacting inner sphere complexes. A simple primitive model is employed for g(r) and the effective contact distance (r/sub min/) is taken as 5.5 A, the value at which the staggered face-to-face configuration of the orthohedral complexes achieves van der waals contact (via the water hydrogen atoms). The electronic coupling information implicit in k/sub el/(r) is obtained from large scale ab initio molecular orbital calculations carried out for the diabatic states of the reactive ion pair. The calculated rate constant, k/sub ex/, and associated activation parameters are in good agreement with experimental data extrapolated to zero ionic strength and correspond to a mechanism dominated by direct Fe-Fe overlap and characterized by a modest degree of nuclear tunnelling and non-adiabatic character.
- Research Organization:
- Brookhaven National Lab., Upton, NY (USA)
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 6406799
- Report Number(s):
- BNL-29896; CONF-8106139-2; ON: DE81026096
- Resource Relation:
- Conference: Symposium on inorganic reaction mechanisms, Detroit, MI, USA, 10 Jun 1981
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
IRON COMPLEXES
ELECTRON EXCHANGE
ACTIVATION ENERGY
AQUEOUS SOLUTIONS
CHEMICAL REACTION KINETICS
QUANTUM MECHANICS
COMPLEXES
DISPERSIONS
ELECTRON TRANSFER
ENERGY
KINETICS
MECHANICS
MIXTURES
REACTION KINETICS
SOLUTIONS
TRANSITION ELEMENT COMPLEXES
640300* - Atomic
Molecular & Chemical Physics
400201 - Chemical & Physicochemical Properties