title: Long Range Proton-Coupled Electron Transfer Reactions of Bis(imidazole) Iron Tetraphenylporphyrins Linked to Benzoates.
abstract: Concerted proton-electron transfer (CPET) reactions in iron carboxy-tetraphenylporphyrin complexes have been investigated using both experimental and theoretical methods. Synthetic heme models abstract H+and e-from the hydroxylamine TEMPOH or an ascorbate derivative, and the kinetics of the TEMPOH reaction indicate concerted transfer of H+and e-. Phenylene linker domains vary the electron donor/acceptor separation by approximately 4 Å. The rate data and extensive molecular simulations show that the electronic coupling decay constant (β) depends on conformational flexibility and solvation associated with the linker domain. Our best estimate of β is 0.23 ± 0.07 Å-1, a value that is near the low end of the range (0.2-0.5 Å-1) established for electron transfer reactions involving related linkers. This is the first analysis of β for a CPET reaction.
authors.affiliation: University of Washington, Department of Chemistry, Box 351700 Seattle, WA 91195-1700 ; California Institute of Technology, Department of Chemistry, 1200 E. California Blvd. Pasadena, CA 91125.
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Warren
authors.forename: Artur R
authors.initials: AR
authors.lastname: Menzeleev
authors.forename: Joshua S
authors.initials: JS
authors.lastname: Kretchmer
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Miller
authors.forename: Harry B
authors.initials: HB
authors.lastname: Gray
authors.forename: James M
authors.initials: JM
authors.lastname: Mayer
keywords: Proton-coupled electron transfer; concerted proton-electron transfer; distance dependence; electronic coupling; molecular dynamics