title: Propeller-shaped fused oligothiophenes: a remarkable effect of the topology of sulfur atoms on columnar stacking.
abstract: Propeller-shaped regioisomers of fused oligothiophenes F9T(endo), F9T(anti), and F9T(exo) were successfully synthesized. DFT calculations indicated that their core parts are distorted from planarity due to intramolecular steric repulsions involving large sulfur atoms. In contrast with soft crystalline F9T(anti) and F9T(exo), F9T(endo) self-assembles into a hexagonal columnar liquid crystal (Col(h) LC), displaying a clear X-ray diffraction (XRD) due to its stacked π-conjugated core. In each LC column, well-organized intermolecular S-S contacts are developed triple-helically along the columnar axis with a helical pitch of 4.04 nm. Among LC semiconductors reported to date, Col(h) LC F9T(endo) displays a top-class charge-carrier mobility (0.18 cm(2) V(-1) s(-1)) with a distinct ambipolar character featuring well-balanced hole and electron mobilities. A thin film, prepared by mixing F9T(endo) with soluble fullerene PCBM, shows a photovoltaic response, when the fullerene content is large enough to compensate a small absorptivity of F9T(endo) for visible light.
authors.affiliation: School of Engineering, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Qi
authors.initials: Q
authors.lastname: Xiao
authors.forename: Tsuneaki
authors.initials: T
authors.lastname: Sakurai
authors.forename: Takahiro
authors.initials: T
authors.lastname: Fukino
authors.forename: Kouki
authors.initials: K
authors.lastname: Akaike
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Honsho
authors.forename: Akinori
authors.initials: A
authors.lastname: Saeki
authors.forename: Shu
authors.initials: S
authors.lastname: Seki
authors.forename: Kenichi
authors.initials: K
authors.lastname: Kato
authors.forename: Masaki
authors.initials: M
authors.lastname: Takata
authors.forename: Takuzo
authors.initials: T
authors.lastname: Aida