Franceschini, M., Crosta, M., Ferreira, R. R., Poletto, D., Demitri, N., Zobel, J. P., González, L., and Bonifazi, D.
J. Am. Chem. Soc. 2022, 144, 47, 21470-21484
Here, we report the synthesis of BN-doped graphenoid nanoribbons, in which peripheral carbon atoms at the zigzag edges have been selectively replaced by boron and nitrogen atoms as BN and NBN motifs. This includes high-yielding ring closure key steps that, through N-directed borylation reaction using solely BBr3, allow the planarization of meta-oligoarylenyl precursors, through the formation of B–N and B–C bonds, to give ter-, quater-, quinque-, and sexi-arylenyl nanoribbons. X-ray single-crystal diffraction studies confirmed the formation of the BN and NBN motifs and the zigzag-edged topology of the regularly doped ribbons. Steady-state absorption and emission investigations at room temperature showed a systematic bathochromic shift of the UV–vis absorption and emission envelopes upon elongation of the oligoarylenyl backbone, with the nanoribbon emission featuring a TADF component. All derivatives displayed phosphorescence at 77 K. Electrochemical studies showed that the π-extension of the peri-acenoacene framework provokes a lowering of the first oxidative event (from 0.83 to 0.40 V), making these nanoribbons optimal candidates to engineer p-type organic semiconductors.