Consecutive Thiophene-Annulation Approach to π-Extended Thienoacene-Based Organic Semiconductors with 1Benzothieno3,2-b1benzothiophene (BTBT) Substructure

We describe a new synthetic route to the 1benzothieno3,2-b1benzothiophene (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., 1benzothieno3,2-bnaphtho2,3-bthiophene, 1benzothieno3,2-banthra2,3-bthiophene, and naphtho3,2-bthieno3,2-banthra2,3-bthiophene, a selenium-containing derivative, 1benzothieno3,2-b1benzoselenophene. It also allows us to access largely π-extended derivatives with two BTBT substructures, e.g., bis1benzothieno2,3-d:2',3'-d'benzo1,2-b:4,5-b'dithiophene and bis1benzothieno2,3-d:2',3'-d'naphtho2,3-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 cm(2) 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.