12b,24b-Diborahexabenzo[a,c,fg,l,n,qr]pentacene: A Low-LUMO Boron-Doped Polycyclic Aromatic Hydrocarbon.

Abstract

Herein we devise and execute a new synthesis of a pristine boron‐doped nanographene. Our target boron‐doped nanographene was designed based on DFT calculations to possess a low LUMO energy level and a narrow band gap derived from its precise geometry and B‐doping arrangement. Our synthesis of this target, a doubly B‐doped hexabenzopentacene (B 2 ‐HBP), employs six net C−H borylations of an alkene, comprising consecutive hydroboration/electrophilic borylation/dehydrogenation and BBr3/AlCl3/2,6‐dichloropyridine‐mediated C−H borylation steps. As predicted by our calculations, B 2 ‐HBP absorbs strongly in the visible region and emits in the NIR up to 1150 nm in o‐dichlorobenzene solutions. Furthermore, B 2 ‐HBP possesses a very low LUMO level, showing two reversible reductions at −1.00 V and −1.17 V vs. Fc+/Fc. Our methodology is surprisingly selective despite its implementation of unfunctionalized precursors and offers a new approach to the synthesis of pristine B‐doped polycyclic aromatic hydrocarbons.