title: Effects of structural factors on the pi-dimerization and/or disproportionation of the cation radical of extended TTF containing thiophene-based pi-conjugated spacers.
abstract: 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.
authors.affiliation: Ingénierie Moléculaire et Matériaux Organiques, CNRS UMR 6501, Université d'Angers 2 Bd Lavoisier, 49045 Angers, France. pierre.frere@univ-angers.fr
authors.forename: Pierre
authors.initials: P
authors.lastname: Frère
authors.forename: Magali
authors.initials: M
authors.lastname: Allain
authors.forename: El Hadj
authors.initials: el H
authors.lastname: Elandaloussi
authors.forename: Eric
authors.initials: E
authors.lastname: Levillain
authors.forename: François-Xavier
authors.initials: FX
authors.lastname: Sauvage
authors.forename: Amédée
authors.initials: A
authors.lastname: Riou
authors.forename: Jean
authors.initials: J
authors.lastname: Roncali