Tri-N-annulated hexarylene: an approach to well-defined graphene nanoribbons with large dipoles

We report a highly efficient synthetic methodology toward tri-N-annulated hexarylenes from easily available N-annulated perylenes, which is favored by the oxidative ring fusion driven by DDQ/Sc(OTf)(3). To assist the characterization of the new compounds, quantum-chemical calculations of structural and spectroscopic properties have been carried out for three oligomers of N-annulated rylenes. It is shown that tri-N-annulated hexarylene dyes display remarkably large dipole moments likely associated with the formation of H aggregates, as suggested by the marked concentration dependence of the measured UV-vis spectra. It is suggested that the combination of pi-pi stacking interactions and dipole-dipole interactions may favor the formation of highly ordered supramolecular structures, resulting in enhanced charge carrier mobilities.