Electron-Transfer Processes in Metal-Free Tetraferrocenylporphyrin. Understanding Internal Interactions To Access Mixed-Valence States Potentially Useful for Quantum Cellular Automata

Redox properties of H(2)TFcP [TFcP(2-) = 5,10,15,20-tetraferrocenylporphyrin(2-)I 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 substituent underwent two very diffuse, two-electron stepwise oxidations. The use of a weakly coordinating TFAB ([NBu4][B(C6F5)(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 result were observed when a DCM/TBAP system and an imidazolium cation-based ionic liquid ((bmim)Tf2N = 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-Fell(III) [H(2)TFcP](4+,) [H(2)TFcp](2+). 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