title: Electron-transfer processes in metal-free tetraferrocenylporphyrin. Understanding internal interactions to access mixed-valence States potentially useful for quantum cellular automata.
abstract: Redox properties of H(2)TFcP [TFcP(2-) = 5,10,15,20-tetraferrocenylporphyrin(2-)] were investigated using cyclic voltammetry, differential pulse voltammetry, and square-wave voltammetry methods in a large variety of solvents and electrolytes. When DMF, THF, and MeCN were used with TBAP as the supporting electrolyte, the first oxidation wave was assigned to a single four-electron oxidation process reflecting simultaneous oxidation of all iron(II) centers into iron(III) centers in H(2)TFcP. When an o-DCB (1,2-dichlorobenzene)/TBAP combination was used in electrochemical experiments, four ferrocene substituents underwent two very diffuse, "two-electron" stepwise oxidations. The use of a weakly coordinating TFAB ([NBu(4)][B(C(6)F(5))(4)]) electrolyte in o-DCB or DCM results in four single-electron oxidation processes for ferrocene substituents in which the first and second single-electron waves have a relatively large separation, while the second, third, and fourth oxidation processes are more closely spaced; similar results were observed when a DCM/TBAP system and an imidazolium cation-based ionic liquid ((bmim)Tf(2)N = N-butyl-N'-methylimidazolium bis(trifluoromethanesulfonyl)imide) were used. Spectroelectrochemical oxidation of H(2)TFcP in o-DCB or DCM with TFAB as the supporting electrolyte allowed for characterization of the mixed-valence [H(2)TFcP](+), [H(2)TFcP](2+), and [H(2)TFcP](3+) compounds by UV-vis spectroscopy in addition to the "all-Fe(III)" [H(2)TFcP](4+). The chemical oxidation of H(2)TFcP was tested using a variety of oxidants which resulted in formation of mixed-valence [H(2)TFcP](+) and [H(2)TFcP](2+) as well as [H(2)TFcP](4+), which were characterized by UV-vis-NIR, MCD, IR, Mossbauer, and XPS spectroscopy. The intervalence-charge-transfer bands observed in the near-IR region in [H(2)TFcP](+) and [H(2)TFcP](2+) complexes were analyzed using Hush formalism and found to be of class II (in Robin-Day classification) character with localized ferrous and ferric centers. Class II behavior of [H(2)TFcP](+) and [H(2)TFcP](2+) complexes was further confirmed by Mossbauer, IR, and XPS data.
authors.affiliation: Department of Chemistry & Biochemistry, University of Minnesota-Duluth, Duluth, Minnesota 55812, USA. vnemykin@d.umn.edu
authors.forename: Victor N
authors.initials: VN
authors.lastname: Nemykin
authors.forename: Gregory T
authors.initials: GT
authors.lastname: Rohde
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Barrett
authors.forename: Ryan G
authors.initials: RG
authors.lastname: Hadt
authors.forename: Claudia
authors.initials: C
authors.lastname: Bizzarri
authors.forename: Pierluca
authors.initials: P
authors.lastname: Galloni
authors.forename: Barbara
authors.initials: B
authors.lastname: Floris
authors.forename: Israel
authors.initials: I
authors.lastname: Nowik
authors.forename: Rolfe H
authors.initials: RH
authors.lastname: Herber
authors.forename: Andrea G
authors.initials: AG
authors.lastname: Marrani
authors.forename: Robertino
authors.initials: R
authors.lastname: Zanoni
authors.forename: Nikolay M
authors.initials: NM
authors.lastname: Loim