An unconventional route to an ambipolar azaheterocycle and its in situ generated radical anion

Abstract

Herein we report the synthesis, characterization and application of an azaheterocycle 4 obtained via an unprecedented C–N coupling. The neutral azaheterocycle undergoes one-electron reduction to form an air-stable radical anion in situ, which provides added benefit towards operational stability of the device during n-type charge transport. The unusual stability of this radical anion is due to the fact that the fused cyclopentane ring upon reduction forms aromatic cyclopentadienyl anion, and the negative charge delocalizes over the nearly planar azaheterocycle core. The present azaheterocycle can be considered as a mimic of a fullerene fragment, which shows balanced ambipolar charge transport in space charge limited current (SCLC) devices with moderate hole (μ_h) and electron (μ_e) mobilities (μ_h = 2.96 × 10⁻³ cm² V⁻¹ s⁻¹ and μ_e = 1.11 × 10⁻⁴ cm² V⁻¹ s⁻¹). Theoretical studies such as nucleus independent chemical shifts (NICS) calculations, anisotropy of the induced current density (ACID) plots, spin density mapping and anisotropic mobility calculations were performed to corroborate the experimental findings.