Experimental and Theoretical Study of the n‐Doped Successive Polyanions of Oligocruciform Molecular Wires: Up to Five Units of Charge |
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Authors: | Dr Abdelaziz Al Ouahabi Dr Paul Baxter Dr Claude Mathis Maxime Bernard Dr Bertrand Vileno Dr Jean‐Paul Gisselbrecht Prof Philippe Turek Dr Jean‐Marie Mouesca Dr Sylvie Choua |
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Institution: | 1. Institut Charles Sadron, CNRS, UPR 22, 23 rue du Loess, 67034 Strasbourg (France);2. Institut de Chimie (UMR 7177), Université de Strasbourg, 4 rue Blaise Pascal, CS 90032, 67081 Strasbourg Cedex (France);3. CEA Grenoble, INAC/SCIB, UMR‐E3 (CEA UJF), 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France) |
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Abstract: | The electronic structure of polyanions of sterically encumbered triisopropylsilyl‐substituted linear and cyclic oligo(phenyleneethynylene)s ( M onomer, T rimer, P entamer, and Tr iangle) is investigated by electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR), and UV/Vis–near‐infrared (NIR) spectroscopies, cyclic voltammetry, and theoretical calculations (DFT). Increasing anion orders are generated sequentially in vacuo at room temperature by chemical reaction with potassium metal up to the pentaanion. The relevance of these compounds acting as electron reservoirs is thus demonstrated. Even‐order anions are EPR silent, whereas the odd species exhibit different signatures, which are identified after comparison of the measured hyperfine couplings by ENDOR spectroscopy with those predicted by DFT calculations. With increasing size of the oligomers the electron spin density is first distributed over the backbone carbon atoms for the monoanions, and then further localized at the outer phenyl rings for the trianion species. Examination of the UV/Vis‐NIR spectra indicates that the monoanions ( T.? , P.? ) exhibit two transitions in the Vis‐NIR region, whereas a strong absorption in the IR region is solely observed for higher reduced states. Electronic transitions of the neutral monoanions and trianions are redshifted with increasing oligomer size, whereas for a given oligomer a blueshift is observed upon increasing the charge, which suggests a localization of the spin density. |
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Keywords: | density functional calculations electronic structure ENDOR spectroscopy EPR spectroscopy polyanions |
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