Two BN Isosteres of Anthracene: Synthesis and Characterization

Abstract

The synthesis of two parental BN anthracenes, 1 and 2, was developed, and their electronic structure and reactivity behavior were characterized in direct comparison with all-carbon anthracene. Gas-phase UV-photoelecton spectroscopy studies revealed the following HOMO energy trend: anthracene, -7.4 eV; BN anthracene 1, -7.7 eV; bis-BN anthracene 2, -8.0 eV. The λmax of the lower energy band in the UV-vis absorption spectrum is as follows: anthracene, 356 nm; BN anthracene 1, 359 nm; bis-BN anthracene 2, 357 nm. Thus, although the HOMO is stabilized with increasing BN incorporation, the HOMO-LUMO band gap remains unchanged across the anthracene series. The emission λmax values for the three investigated anthracene compounds are at 403 nm. The pKa values of the N-H proton for BN anthracene 1 and bis-BN anthracene 2 were determined to be approximately 26. BN anthracenes 1 and 2 do not undergo heat- or light-induced cycloaddition reactions or Friedel-Crafts acylations. Electrophilic bromination of BN anthracene 1 with Br2, however, occurs regioselectively at the 9-position. The reactivity behavior and regioselectivity of bromination of BN anthracenes are consistent with the electronic structure of these compounds; i.e., (1) the lower HOMO energy levels for BN anthracenes stabilize the molecules against cycloaddition and Friedel-Crafts reactions, and (2) the HOMO orbital coefficients are consistent with the observed bromination regioselectivity. Overall, this work demonstrates that BN/CC isosterism can be used as a molecular design strategy to stabilize the HOMO of acene-type structures while the optical band gap is maintained.

Pristine and BN doped graphyne derivatives for UV light protection

“…Their study demonstrated that the HOMO energy level shows a decreasing trend with increasing BN unit for BN isoteres of antracene and increasing trend with increasing BN unit for BN substituted tolan . More interestingly, the replacement of one unit of CC by BN shifts the toward higher wavelengths (lower energy) but replacement of all carbon atoms of benzene by alternative arrangement of boron and nitrogen (borazine) shifts the toward lower wavelength (higher energy). Hexagonal boron nitride (h‐BN) forms various structurally analogous to carbon allotropes.…”

Synthesis and Characterization of 1,2‐Azaborine‐Containing Phosphine Ligands: A Comparative Electronic Structure Analysis

“…The syntheses of 1 and 2 are illustrated in Scheme . Treatment of the known azaborine precursor 3 [6c] with the corresponding potassium di(aryl)phosphide [generated in situ from potassium hydride and di(aryl)phosphine] furnished the desired products 1 and 2 in 73 and 79 % yield, respectively.…”

“…Research in our group explores the fundamental properties and applications of 1,2‐dihydro‐1,2‐azaborines (henceforth referred to as azaborines), which are arene isosteres that have a C=C unit replaced with an isoelectronic B–N unit . The resulting aromatic boron(B)‐nitrogen(N) heterocycles have structures similar to their all‐carbon analogues but different electronic properties due to the introduction of a polarized B–N bond . The inherent differences between C–C and B–N bonds make the substitution of an azaborine moiety into classic all‐carbon arene systems interesting from a synthetic and fundamental point‐of‐view.…”

“…However, no all‐carbon‐containing, direct structural analogues exist with which to compare these B–P‐bond‐containing ligands. On the other hand, the structural similarity between 1,2‐azaborine and benzene will allow us to directly compare the properties of the azaborine‐containing phosphine ligand with those of its carbonaceous counterpart . Herein, we report the synthesis of two azaborine‐containing phosphine ligands, a BN analogue of tri‐ o ‐tolylphosphine (compound 1 ) and a BN analogue of diphenyl( o ‐tolyl)phosphine (compound 2 ).…”

Optoelectronic properties of higher acenes, their BN analogue and substituted derivatives

“…BN substitution of carbon based materials is frequently used procedure for obtaining materials with improved physico-chemical properties. This procedure is also known as BN/CC isosterism and means replacement of a C]C unit with the isosteric BeN unit [18,19] After dealing with interesting curved organic molecule, sumanene [45e49], in this work we decided to investigate the optoelectronic properties of planar organic structures -higher acenes which consist of linearly fused benzene rings (ranging 5 to 10, from pentacene to decacene), their BN analogues and hybrid structures obtained by BN substitution of higher acenes. Namely, we calculated oxidation and reduction potentials (OP and RP respectively) and electron and hole reorganization energies (ERE and HRE respectively).…”