Solvent Relaxation in Electron-Transfer Reactions: Comparisons between Barrier-Crossing Dynamics in Water and Polar Aprotic Media
Abstract
Rate constants, k sub ex, for electron self exchange of three metallocene redox couples, carboxymethyl (cobaltocenium-cobaltocene) CpCO2Me2) 2Co+o, hydroxymethyl (ferrocenium-ferrocene) (Cp (dot) CpCH2OH)Fe+/o, and trimethylaminomethyl (ferrocenium-ferrocene) (Cp (dot) CpCH2NMe3)Fe2+/2, obtained using proton NMR line broadening, are utilized along with optical electron-transfer energies for the mixed-valence biferrocenylacetylene cation to obtain solvent-dependent frequencies, (Kappa sub el)(n sub n), in water relative to those in methanol and six aprotic solvents. While (Kappa sub el)(n sub n) for the ferrocene couples is insensitive to the solvent, indicative of nonadiabatic behavior (K sub el < 1), K sub el (n sub n) vn for the cobaltocene couple is responsive to the solvent dynamics. While rapid barrier-crossing dynamics are obtained in water, comparable to acetonitrile, acetone, and nitromethane, the influence of high-frequency relaxation components in water is less marked than for methanol. Keywords: Nuclear: Magnetic resonance: Metallocene redox couples: Line broadening: Biferrocenylacetylene cation: Aprotic solvents: Solvent dynamics: Mixed valence.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1989
- Accession Number
- ADA210212
Entities
People
- George E. Mcmanis
- Michael J. Weaver
- Roger M. Nielson
Organizations
- Purdue University