BN-Acene Ladder with Enhanced Charge Transport for Organic Field-Effect Transistors.

The in-depth research on the charge transport properties of BN-embedded polycyclic aromatic hydrocarbons (BN-PAHs) still lags far behind studies of their emitting properties. Herein, we report the successfully synthesis of novel ladder-type BN-PAHs (BCNL1 and BCNL2) featuring a highly ordered BC3N2 acene unit, achieved via a nitrogen-directed tandem C-H borylation. Single-crystal X-ray diffraction analysis unambiguously revealed their unique and compact herringbone packing structures. Micro-sized single-crystalline organic field-effect transistors (OFETs) demonstrated that an enhanced charge transport capability, with BCNL2 achieving a hole mobility of up to 0.62 cm2 V-1 s-1-three orders of magnitude higher than that of BCNL1 (μh max=6 × 10-4 cm2 V-1 s-1), ranking among the highest values for BN-PAHs-based OFETs. Detailed calculations attribute this significant enhancement in the hole mobility to the marked reduction in reorganization energy (λ) of BCNL2, resulting from the five-membered pyrrole ring annulation and molecular skeleton elongation. This work provides insight into molecular design principles for potential BN-PAHs in optoelectronic applications.