Regioisomeric Control of Charge Transport Properties in Fluoranthene-Fused 12-Ring Heteroarenes

Heteroarene-based organic semiconductors (OSCs) have emerged as promising material candidates for large-area, flexible electronic and photonic devices due to their favorable π-conjugation systems and tunable optoelectronic properties. However, their development is still hindered by synthetic and design challenges, in particular, the limited access to highly polycyclic heteroarenes with tunable properties and the unexplored effects of topological isomerism. Here, we have successfully synthesized three regioisomeric thienoacenes (BTFA4-6) by fusing a dicyanofluoranthene unit, which have an identical 12-fused ring composition but different molecular topologies with [a] or [c]-fusion and syn or anti-CN substitution. We demonstrate that solution-processable BTFA4-6 exhibits topology-dependent charge transport properties by fabricating organic field-effect transistors. BTFA4 with [a]-fusion and syn-CN substitution and BTFA6 with [c]-fusion and syn-CN substitution show only typical n-type semiconducting behavior, with electron mobilities of 3.91 × 10^-4 and 1.58 × 10^-5 cm² V^-1 s^-1, respectively, while BTFA5 with [a]-fusion and anti-CN substitution achieves electron-dominated ambipolar behavior, with an increase in electron mobility (3.45 × 10^-2 cm² V^-1 s^-1) by 2 orders of magnitude and a hole mobility of 4.31 × 10^-3 cm² V^-1 s^-1. Therefore, this work establishes that regioisomeric molecular engineering is a powerful tool for manipulating the charge transport properties of heteroarene-based OSCs.