El Hadj Elandaloussi

Control of the bandgap of conducting polymers by rigidification of the π-conjugated system

Rigidification of E-1,2(2,2′-dithienylethylene) by bridging the thiophene rings with the central double bond leads to a ca. 0.40 eV decrease of the bandgap of the resulting conducting polymer.

Effects of Structural Factors on the π‐Dimerization and/or Disproportionation of the Cation Radical of Extended TTF Containing Thiophene‐Based π‐Conjugated Spacers

The electrochemical and chemical oxidation of extended TTF 4 and 5 are analysed by cyclic voltammetry, Visible/NIR and ESR spectroscopies, and the X-ray structures of the new salts 5 x BF(4)(CH(2)Cl(2)) and 4 x ClO(4)(THF)(1/2) are presented. The effects of structural factors on the pi-dimerization or the disproportionation reaction of the cation radical are shown. The oxidation of compound 4 presents the successive formation of stable cation radical and dication species both in dichloromethane (DCM) and in a CH(3)CN/THF mixture. In contrast, for compound 5, the stability of the oxidation states strongly depends on the nature of the solvent. In DCM, the oxidation of 5 proceeds by two close one-electron transfers while in CH(3)CN/THF the dication is directly formed via a two-electron process. The X-ray structures of the two salts reveal the formation of pi-dimers of cation radical. While the dimer (5(2))(2+) is due mainly to pi-pi interactions between the conjugating spacer, the multiplication of the sulfur atoms in compound 4 contributes to stabilize the dimer by the combined effects of S-S and pi-pi interactions. Visible/NIR and ESR experiments confirm the higher tendency of 4(+)(.) to dimerize with the occurrence of dimer and monomer in solution, while for 5(+)(.) only the monomer is detected in DCM. On the other hand, by dissolution of 5 x BF(4)(CH(2)Cl(2)) in CH(3)CN, only the neutral and the dicationic states of compounds 5 are observed owing to the disproportionation reaction.

Oligo(furan-2,5-diylvinylene)s as π-conjugating spacers in linearly extended hybrid tetrathiafulvalene analogues

The synthesis of a new series of push–push systems based on furan-2,5-diylvinylene oligomers end-capped with l,3-dithiol-2-ylidene electron-releasing groups is described. 1H NMR spectroscopy and X-ray diffraction reveal that the molecules adopt a planar conformation stabilized by strong intramolecular interactions. Electronic absorption spectroscopy indicates that the effective conjugation length increases steadily with the length of the π-conjugated system without any evidence of saturation. Analysis of electrochemical behaviour by cyclic voltammetry shows that, whereas all compounds are easily oxidized into stable dications, with extension of the conjugation length the oxidation process progressively evolves from two successive one-electron steps to a single step two-electron transfer.

SOLUBLE THIENYLENEVINYLENE OLIGOMERS END-CAPPED WITH 1,3-DITHIOLE-2-YLIDENE GROUPS

Abstract The synthesis of thienylenevinylene oligomers end-capped with 1,3-dithiole-2-ylidene is described. CV analysis shows that these compounds can be oxidized up to their tetracationic state within a narrow potential window

A cation radical salt of an extended tetrathiafulvalene analogue with a difurylethylene spacer

The X-ray structure of a single crystal of the neutral donor 1b and its electrocrystallized cation radical salt, 1b·ClO4, have been analysed. Both the neutral and the oxidized states adopt a syn conformation stabilized by strong intramolecular interactions that allow the preservation of a planar conformation during the oxidation of 1b.

Extensively π-conjugated solubleoligothienylenevinylenes

Soluble oligothienylenevinylenes are synthesized; the longest oligomers exhibit small bandgaps and can be oxidized to the dication by a two-electron transfer.