Electron-transfer processes in 3,4-diferrocenylpyrroles: Insight into a missing piece of the polyferrocenyl-containing pyrroles family

Wil R. Goetsch, Pavlo Solntsev, Casey Van Stappen, Anatolii A. Purchel, Semen V. Dudkin, Victor N. Nemykin

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Abstract

3,4-Diiodo-1-(triisopropylsilyl)-1H-pyrrole (1), 3,4-diferrocenyl-1- (triisopropylsilyl)-1H-pyrrole (2), and 3,4-diferrocenyl-1H-pyrrole (3) were prepared and characterized using spectroscopic methods and X-ray crystallography. UV-vis spectra of 2 and 3 were correlated with their density functional theory (DFT)-calculated electronic structures as well as theoretically predicted by the time-dependent (TD) DFT-calculations vertical excitation energies. Redox properties of 2 and 3 were investigated using cyclic voltammetry, differential pulse voltammetry, and spectroelectrochemical approaches. Ferrocene-centered oxidation processes in 2 and 3 were found to be separated by ∼180 and ∼300 mV in DCM/TBAP and DCM/(NBu 4)[B(C6F5)4] systems, respectively. Stepwise spectroelectrochemical oxidation of 2 and 3 allowed us to obtain spectroscopic signatures of the mixed-valence [2]+ and [3] + cations. Hush analysis of the intervalence charge-transfer band in [2]+ and [3]+ is suggestive of class II (in Robin and Day classification) mixed-valence behavior. Electronic structures of neutral and spin-localized/delocalized single-electron oxidized mixed-valence cations of 2,5-di-, 3,4-di-, and 2,3,4,5-tetraferrocenylpyrroles were investigated by DFT calculations to resolve current uncertainties regarding the first oxidation process of tetraferrocenylpyrrole.

Original languageEnglish (US)
Pages (from-to)145-157
Number of pages13
JournalOrganometallics
Volume33
Issue number1
DOIs
StatePublished - Jan 13 2014

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