Electron-Transfer Processes in 3,4-Diferrocenylpyrroles: Insight into a Missing Piece of the Polyferrocenyl-Containing Pyrroles Family

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• 作者：Wil R. Goetsch ; Pavlo V. Solntsev ; Casey Van Stappen ; Anatolii A. Purchel ; Semen V. Dudkin ; Victor N. Nemykin
• 刊名：Organometallics
• 出版年：2014
• 出版时间：January 13, 2014
• 年：2014
• 卷：33
• 期：1
• 页码：145-157
• 全文大小：674K
• ISSN：1520-6041

文摘

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鈥搗is 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/(NBu₄)[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.