We describe a new synthetic route to the benzothieno[3,2-b] benzothiophene (BTBT) substructure featuring two consecutive thiophene-annulation reactions from o-ethynyl-thioanisole substrates and arylsulfenyl chloride reagents that can be easily derived from arylthiols. The method is particularly suitable for the synthesis of unsymmetrical derivatives, e.g., benzothieno[3,2-b]naphtho[2,3-b]thiophene, benzothieno[3,2-b] anthra[2,3-b]thiophene, and naphtho[3,2-b]thieno[3,2-b]anthra[2,3-b]thiophene, a selenium-containing derivative, benzothieno[3,2-b]benzoselenophene. It also allows us to access largely π-extended derivatives with two BTBT substructures, e.g., bisbenzothieno[2,3-d:2′,3′-d′]benzo[1, 2-b:4,5-b′]dithiophene and bisbenzothieno[2,3-d:2′,3′- d′]naphtho[2,3-b:6,7-b′]dithiophene (BBTNDT). It should be emphasized that these new BTBT derivatives are otherwise difficult to be synthesized. In addition, since various substrates and reagents, o-ethynyl-thioanisoles and arylthiols, respectively, can be combined, the method can be regarded as a versatile tool for the development of thienoacene-based organic semiconductors in this class. Among the newly synthesized materials, highly π-extended BBTNDT afforded very high mobility (>5 cm2 V-1 s-1) in its vapor-deposited organic field-effect transistors (OFETs), which is among the highest for unsubstituted acene- or thienoacenes-based organic semiconductors. In fact, the structural analyses of BBTNDT both in the single crystal and thin-film state indicated that an interactive two-dimensional molecular array is realized in the solid state, which rationalize the higher carrier mobility in the BBTNDT-based OFETs.
ASJC Scopus subject areas
- Colloid and Surface Chemistry