Ambipolar Organic Field-Effect Transistors Based on Indigo Derivatives

In order to improve the ambipolar performance of indigo-based semiconductors, we have investigated halogen-substituted (1 - 4) and phenyl-substituted (5) indigo derivatives at the 5-position. We show that introduction of iodine atoms, namely 5,5'-diiodoindigo (4), leads to the strong halogen-halogen interaction (iodine-iodine interaction) that gives a significant effect on the molecular packing. Thanks to the supramolecular network coming from the extra iodine-iodine interaction, the molecules are arranged approximately perpendicular to the substrate in the thin film. This results in remarkable transistor performance of the maximum hole and electron mobilities (µh/µe) = 0.42/0.85 cm2V–1s–1, which are one of the highest among small-molecule ambipolar organic transistors. Furthermore, introducing phenyl groups, 5 improves the transistor performances up to the maximum mobilities µh/µe = 0.56/0.95 cm2V–1s–1. We have found that the phenyl groups destroy the standard molecular packing of indigo to achieve a unique structure that is a hybrid of the herringbone and brickwork structures

fosB Grene Products Trigger Cell Proliferation and Morphological Alteration with an Increased Expression of a Novel Processed Form of Galectin-1 in the Rat 3Y1 Embryo Cell Line

In this study, we established rat 3Y1 embryo cell lines expressing FosB and AFosB as fusion proteins (ER-FosB, ER-AFosB) with the ligand-binding domain of human estrogen receptor (ER). The binding of estrogen to the fusion proteins resulted in their nuclear translocation. After estrogen administration, exponentially growing cells expressing ERAFosB, and to a lesser extent ER-FosB, underwent morphological alteration from the flat fibroblastic shape to an extended bipolar shape, and ceased proliferating. Such morphological alteration was also induced in quiescent cells expressing ER-AFosB and ER-FosB after one round of cell division triggered by estrogen administration. The cells expressing ER-AFosB changed shape frequently, and the content of F-actin in the cytoplasm detected by binding of Alexa 488-phalloidin significantly decreased after the morphological alteration. By two-dimensional gel electrophoresis analysis of cellular proteins from the cells expressing ER-AFosB, we identified several proteins whose expression either increased or decreased after estrogen administration. Two of these proteins were identified from their amino acid sequences as novel processed form of galectin-1

Dihedral-Angle Dependence of Intermolecular Transfer Integrals in BEDT-BDT-Based Radical-Cation Salts with θ-Type Molecular Arrangements

We report the structural and physical properties of a new organic Mott insulator (BEDT-BDT)AsF6 (BEDT-BDT: benzo[1,2-g:4,5-g′]bis(thieno[2,3-b][1,4dithiin). This AsF6 salt has the same structure as the PF6 salt. Although the anions are disordered, the donor molecules form a θ-type arrangement. The temperature dependence of the resistivity exhibits semiconducting behavior. The static magnetic susceptibility follows Curie–Weiss law over a wide temperature range; however, below 25 K, the magnetic susceptibility is in agreement with a one-dimensional chain model with the exchange coupling J = 7.4 K. No structural phase transition was observed down to 93 K. At 270 K, the Fermi surface calculated by the tight-binding approximation is a two-dimensional cylinder; however, it is significantly distorted at 93 K. This is because the dihedral angles between the BEDT-BDT molecules become larger due to lattice shrinkage at low temperatures, which results in a smaller transfer integral (t1) along the stack direction. This slight change in the dihedral angle gives rise to a significant change in the electronic structure of the AsF6 salt. Radical-cation salts using BEDT-BDT, in which the highest occupied molecular orbital does not have a dominant sign throughout the molecule, are sensitive to slight differences in the overlap between the molecules, and their electronic structures are more variable than those of conventional θ-type conductors

Charge-Transfer Complexes of Benzothienobenzothiophene with Tetracyanoquinodimethane and the n‑Channel Organic Field-Effect Transistors

n-Channel organic transistors with excellent air stability are realized on the basis of charge-transfer complexes, (BTBT)­(TCNQ), (BTBT)­(F₂TCNQ), (BSBS)­(F₂TCNQ), and (BTBT)­(F₄TCNQ), where BTBT is benzothieno­[3,2-<i>b</i>]­benzo­thiophene, BSBS is benzo­seleno­[3,2-<i>b</i>]­benzo­selenophene, and F_<i>n</i>TCNQ (<i>n</i> = 0, 2, and 4) are fluorinated 7,7,8,8-tetracyanoquinodimethanes. These complexes consist of mixed stacks of essentially neutral molecules, and the transistors are air stable even after several-month storage in ambient conditions