B₂,N₄-Doped Heptacenes: Ambipolar Charge-Transfer Compounds with Deep LUMO Levels

Abstract

The B 2 ,N 4 -doped heptacene H4 in which two N,N′dihydrophenazine units are linked by two BMes bridges (Mes = mesityl) was synthesized via fourfold Buchwald−Hartwig coupling between 2,3,6,7-tetrachloro-9,10-dimesityl-9,10-dihydro-9,10-diboraanthracene and o-phenylenediamine (tBuXPhos-Pd-G3, DBU/NaOTf, 2-MeTHF, 50 °C, 16 h). Upon exposure to ambient air, H4 is oxidized to its N,N′-dihydro form H2; further oxidation with MnO 2 furnishes the di(phenazine) derivative H0.Stirring under a blanket of H 2 in the presence of Pd/C hydrogenates H0 back to H2 and ultimately H4. Yellow-colored H0 is a remarkably good electron acceptor with a LUMO-energy level of −3.9 eV; upon irradiation with a 405 nm LED in the presence of THF or 1,4-cyclohexadiene, H0 accepts two H atoms to furnish H2. One-electron reduction of H0 yields the isolable radical-anion salt Li[H0] (lithium naphthalenide, THF, −30 °C to rt). The ambipolar compounds H2 and H4 possess a navy blue and deep purple color, respectively, due to charge-transfer interactions from the electron-rich N,N′-dihydrophenazine donor(s) to the electron-accepting B 2 C 4 core.

BN‐Isosteres of Nonacene with Antiaromatic B2C4 and N2C4 Heterocycles: Synthesis and Strong Luminescence**

“…During the preparation of this manuscript, Wagner et al. reported the synthesis of B 2 N 4 ‐doped heptacenes containing the similar B 2 C 4 and N 2 C 4 rings but with different numbers of boron and nitrogen atoms [12] . The antiaromaticity of such heterocycles and the redox reactivities of the novel B 2 N 4 ‐doped heptacenes have been systematically investigated.…”

Optimizing stability through conformational locking and ring fusion modulation in organic semiconductors

“…1–8 Incorporation of heteroatoms into a conjugated ladder framework leads to the formation of heteroacenes. These moieties are synthesized through various ring-closure strategies, 7 including stepwise ladderization, 9 heteroannulation, 5,10,11 reductive cyclization, 11–14 oxidative cyclization, 15 acid catalysed condensation, 8 B,N-embedding, 16,17 and imide bridge installation. 18 Incorporation of electron-withdrawing groups ( e.g.…”