Simple synthesis of alkyl derivatives of tetrathienoacene and their application in organic field-effect transistors

Friedel–Crafts acylation of tetrathienoacene (TTA) followed by a reduction reaction resulting in various octyl-substituted TTA derivatives is described for the first time. Varying conditions of the acylation reaction allowed control over the formation of mono- or diketones, which were further reduced to mono- or dialkyls. It was shown that an alkyl group can be introduced either in α, β, or both positions of TTA in a controllable way. Optical, thermal, electrochemical and semiconducting properties of the mono and dioctyl substituted derivatives of TTA are presented. Small and wide-angle diffraction investigations made it possible to attribute the P2 monoclinic crystal structure for C8-TTA-C8 and mesophase existence for C8-TTA at room temperature. Top-contact bottom gate OFETs with a C8-TTA-C8 active layer fabricated by vacuum deposition or solution processing showed similar characteristics pointing out its good processability.