Periphery Fusion Strategy of a Carbazole-Based Macrocycle toward Coplanar N-Heterocycloarene for High-Mobility Single-Crystal Transistors.

Abstract

Designing (hetero)cycloarenes through the modifications of the π-topology and molecular packing of organic semiconductors has recently garnered considerable attention. However, their applications as an organic active layer in field-effect transistors are very limited, and the obtained hole carrier mobilities are less than 1 cm² V^-1 s^-1 . In this work, a novel alkyl-substituted coplanar N-heterocycloarene (FM-C4) containing four carbazole units is successfully synthesized in crystalline form. As compared to the corresponding single-bond-linked carbazole-based macrocycle M-C4, it is found that the periphery fusion strategy greatly changes the electronic structures, energy levels, photophysical properties, host-guest interactions with fullerenes, and molecular crystal stacking motifs. In particular, the fully fused N-heterocycloarene FM-C4 exhibits a herringbone packing structure with an unusual long-range π-π overlap distance as low as 3.19 Å, whereas the single crystal of M-C4 demonstrates no π-π interactions. As a consequence, FM-C4 in single-crystal transistors displays the highest hole mobility of 2.06 cm² V^-1 s^-1 , significantly outperforming M-C4 and all the reported (hetero)cycloarenes and suggesting the high potential of (hetero)cycloarenes for organic electronic applications.