title: Experimental and theoretical study of the n-doped successive polyanions of oligocruciform molecular wires: up to five units of charge.
abstract: The electronic structure of polyanions of sterically encumbered triisopropylsilyl-substituted linear and cyclic oligo(phenyleneethynylene)s (Monomer, Trimer, Pentamer, and Triangle) 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.
authors: Institut Charles Sadron, CNRS, UPR 22, 23 rue du Loess, 67034 Strasbourg, France.
authors: Abdelaziz
authors: A
authors: Al Ouahabi
authors: Paul
authors: P
authors: Baxter
authors: Claude
authors: C
authors: Mathis
authors: Maxime
authors: M
authors: Bernard
authors: Bertrand
authors: B
authors: Vileno
authors: Jean-Paul
authors: JP
authors: Gisselbrecht
authors: Philippe
authors: P
authors: Turek
authors: Jean-Marie
authors: JM
authors: Mouesca
authors: Sylvie
authors: S
authors: Choua