Dynamic Solvent Effects on Electron Transfer Rates in the Inverted Regime: Ultrafast Studies on the Betaines
Abstract
Transient pump-probe measurements have been made on Betaine-30, the solvent polarity probe. Betaine-30 is composed of organic donor and acceptor groups. The transient data has been analyzed to measure k sub et the electron transfer (et) rate constant, in polar solvents for this inverted regime et. The observed rate constant, in various polar solvents is as much as a factor of 100, 000 larger than is predicted by the standard, classical, implementation of the theory of Sumi and Marcus, using Kjaer and Ulstrup's estimates for necessary parameters. In contrast, a quantum treatment of the vibrational modes by Jortner and Bixon, which includes the dynamic solvent effect, predicts that the rate should be approximately k sub et, JB=1/< tau sub s>. This is close to the experimental results in typical polar aprotic solvents. The kinetic behavior of Betaine-30 in slowly relaxing solvents is shown to be in the 'diffusionless limit' of the hybrid, generalized Sumi-Marcus/Jortner-Bixon picture.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 06, 1991
- Accession Number
- ADA235884
Entities
People
- Eva Akesson
- Gilbert C. Walker
- Paul F. Barbara
Organizations
- University of Minnesota