Accession Number:

ADA210206

Title:

The Role of Solvent Dynamics in Electron Transfer: Electrochemical Exchange Kinetics of Cobalt Clathrochelates as a Probe of Reactant Vibrational Effects

Descriptive Note:

Technical rept. no. 81, 1 Oct 1987-30 Jun 1989

Corporate Author:

PURDUE UNIV LAFAYETTE IN DEPT OF CHEMISTRY

Report Date:

1989-07-01

Pagination or Media Count:

9.0

Abstract:

Rate constants for electrochemical exchange, kex, have been measured for the cobalt clathrochelate couples Codmg 3 BF 20 and Codmg 3 BC4H9 20 dmgdouble deprotonated dimethylglyoxime at gold and mercury electrodes in six solvents so to ascertain if the solvent relaxation dynamics provide a significant contribution to the solvent-dependent reaction rates. Unlike most systems examined previously with regard to solvent dynamical effects, a substantial component of the activation barrier for the cobalt clathrochelate couples is associated with inner-shell reactant vibrational distortions in addition to outer-shell solvent reorganization. The solvents examined, acetonitrile, acetone, methylene chloride, benzonitrile, nitrobenzene, and propylene carbonate, were chosen so to provide large up to ca. 30 fold variations in the frequency of overdamped solvent relaxation, os. The relative barrier-crossing frequencies, n, extracted from the kex values by correcting for the solvent-dependent activation barriers show a marked dependence upon indicating that overdamped solvent relaxation contributes significantly to the barrier-crossing frequency for these systems. Reprints.

Subject Categories:

  • Physical Chemistry

Distribution Statement:

APPROVED FOR PUBLIC RELEASE