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 CÀ H borylations of an alkene, comprising consecutive hydroboration/electrophilic borylation/dehydrogenation and BBr 3 /AlCl 3 /2,6-dichloropyridine-mediated CÀ 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 À 1.00 V and À 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.

Structure and Electronics of a Series of CAAC-Stabilized Diboron-Doped Acenes from 1,4-Diboranaphthalene to 6,13-Diborapentacene

“…Boron doping of PAHs has been shown to decrease their HOMO–LUMO (H–L) gap significantly, mainly through the participation of the empty boron p z orbital in the LUMO and often more efficiently than the extension of the PAH framework itself. , Stable dihydrodiboraacenes, i.e., n -acenes in which two CR units (R = anionic substituent) have been replaced by isosteric (but not isoelectronic) BR units, have been prepared up to n = 9 from simple precursors through Si–B metathesis and/or C–H borylation reactions and show strong luminescence or emission in the near-IR region. − Air-stable 9,10-dihydro-9,10-diboraanthracene (9,10-R 2 -DHDBA) derivatives, in particular, have shown great promise in OLED applications. − …”

Progress of Polycyclic Boron-Doped Molecular Carbons

“…This group further devised and executed a new synthesis for BMCs based on the above strategy. 18c The consecutive hydroboration/electrophilic borylation/dehydrogenation and BBr 3 /AlCl 3 /2,6-dichloropyridine-mediated C–H borylation steps afforded the BMC 24 . The single-crystal structure of 24 shows a moderately planar π-surface and thus exhibits 1D columnar π-stacking with an intermolecular packing distance of 3.4 Å.…”

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

“…4,30 Thus, H0 has an ideal design to qualify as a "deep LUMO material" [E(LUMO) < 3.0 eV] 31 as they are in high demand for a wide range of applications. 32,33 We will show that H0 can be reduced not only by injection of one electron to furnish the thoroughly characterized radical anion [H0] •− but also by single or double addition of H 2 across its phenazine sites to form H2 and H4 (our nomenclature refers to the number of H atoms that are attached to the N sites in our B 2 ,N 4 -heptacenes). The sequence H0/H2/H4 is chemically fully reversible and takes the system from an A−A−A to a D−A−A and finally a D−A−D triad with fundamentally different optoelectronic behaviors (D: π-electron donor; A: π-electron acceptor).…”