Two dodecyl-substituted angular anthradithiophene isomers (C12-α-ADT and C12-β-ADT) were synthesized and systematically characterized to investigate the influence of the thiophene-fusion pattern on their molecular packing and charge-transport properties. C12-α-ADT displays a uniform π-conjugation distribution, and its inward-directed S atoms enable symmetric S···H interactions between π-cores and favor a layered π-slipped packing. Unlike C12-α-ADT, C12-β-ADT exhibits more localized aromaticity, and its outward-directed S atoms disfavor close π-core contacts, resulting in an interdigitated alkyl-chain-π-core packing without π–π overlap. In addition, C12-α-ADT and C12-β-ADT films both form ordered layered structures via a blade coating. C12-α-ADT exhibits consistent molecular packing between its film and single crystal, yielding a mobility of 1.88 cm2 V–1 s–1, whereas C12-β-ADT undergoes orientation reconstruction, showing a film orientation distinctly different from that of its single crystal and poorer crystallinity, resulting in a much lower mobility of 0.18 cm2 V–1 s–1. This study reveals that the thiophene-fusion pattern plays critical roles in tuning molecular π-conjugation and packing, film-formability, and carrier transport, offering useful guidelines for designing high-performance thienoacene-based semiconductors.
Yang et al. (Tue,) studied this question.