Crystal Engineering of Dibenzothiophenothieno3,2-bthiophene (DBTTT) Isomers for Organic Field-Effect Transistors

Three thiophene ring-terminated benzothieno3,2-bbenzothiophene (BTBT) derivatives, C-C6-DBTTT, C-C12-DBTTT, and L-C12-DBTTT, were designed and synthesized, differing in the isomerization of alkyl chain position as well as aromatic core construction. A study of crystal structure and electronic properties combined with a theoretical investigation was performed to understand the structure–property relationships for the application of these molecules in organic field-effect transistors (OFETs). Different crystal packing structures were observed for these three isomers by single-crystal X-ray diffraction as a result of a crystal engineering molecular design approach. The highest charge-carrier mobility was observed for the isomer with a collinear core, L-C12-DBTTT. Preliminary results demonstrated a promising hole mobility of 2.44 cm2 V–1 s–1, despite the polymorphism observed in ambient conditions.