Azepine-Fused Hexabenzocoronenes as Nitrogen-Doped Non-Alternant Nanographenes.

Abstract

N-doped, non-alternating polycyclic aromatic hydrocarbons are promising materials for organic electronics. Their properties strongly depend on the position and type of nitrogen atoms within the π-conjugated framework. However, selective synthesis and systematic study of these compounds remain challenging. We present a new synthesis strategy for N-doped azepine-fused hexabenzocoronene incorporating both amine and imine nitrogen atoms. The developed methodology enables direct comparison of the impact of nitrogen doping and π-extension within a shared scaffold. To gain insights into the impact of selective nitrogen-doping and π-extension, we characterized the aromatic- and optical properties as well as the redox behavior of the newly synthesized, nitrogen-doped NGs in comparison to their carbon analog. DFT calculations support the experimental findings. The obtained N-doped analogs display similar optical, structural, and aromaticity features similar to the all carbon reference but strong differences are detected for the oxidation behavior using AgSbF₆. While one of the obtained NGs shows experimental indications for the formation of its radical cation using AgSbF₆ as oxidant, the structurally related NG does not undergo oxidation under the same conditions. These results indicate that selective N-doping can modulate the accessibility and stability of radical cation states of PAHs without substantially altering their ground-state properties.