Open-Shell Effects on Optoelectronic Properties: Antiambipolar Charge Transport and Anti-Kasha Doublet Emission from a N-Substituted Bisphenalenyl.

By stabilizing unpaired spin in the ground state, open-shell π-conjugated molecules can achieve optoelectronic properties that are inaccessible to closed-shell compounds. Here, we report the synthesis and characterization of a N-substituted, bisphenalenyl π-radical cation [3(OTf)] that shows antiambipolar charge transport and fluorescence via anti-Kasha doublet emission. 3(OTf) produces a red emission (634-659 nm) by radiative decay from β-LUMO to β-SOMO, based on density functional theory and configuration interaction singles calculations, and records one of the highest photostabilities (t1/2 = 9.5 × 104 s) among fluorescent radicals. Characterization of 3(OTf)-based field-effect transistors reveals that the observed electrical conductivity (σRT ≤ 1.3 × 10-2 S/cm) is enabled by hole and electron transport (μe/μh ≤ 5.70 × 10-5 cm2 V-1 s-1) that is most efficient in the absence of gating, which represents the first example of antiambipolarity in a molecular material.