BNB-doped phenalenyls – aromaticity switch upon one-electron reduction

Abstract

Fully aromatic, luminescent, and highly robust BNB-doped phenalenyls have been prepared, which are isoelectronic to the phenalenyl cation. B-Fluoromesityl-substitution leads to fluorescence in an extremely narrow range and significant increase...

Dithiophene‐Fused Oxadiborepins and Azadiborepins: A New Class of Highly Fluorescent Heteroaromatics

“…The twist angles between the thiophene rings are 7.00(10) (5 Tip ) and 11.4(2)8 ( 7 tively. The B À N bond lengths in 7 Tip are 1.434( 5) and 1.445 (5) , which is in the same range with those in derivatives of H [14,15] and typical BN aromatics, [10] but shorter than in F (1.463(1) ) [12] and G (1.46 ). [13] The UV-vis absorption spectra for 5 Tip , 6 Tip , 7 Tip , 5 FMes , and 6 FMes in CH 2 Cl 2 display one structured low-energy band each with a maximum at 366-376 nm (Figure 3 a, Table 1).…”

“…Computations on this species showed that its BN‐containing rings are nonaromatic, while aromatic character is confined to the three peripheral carbonaceous rings (also here, the two B ‐Mes groups induce some distortion of the PAH plane). Wagner's group and ours independently explored the BNB‐doped phenalenyl system H , wherein such steric stress is effectively prevented [14, 15] . Via in‐depth theoretical studies using nucleus‐independent chemical shift (NICS) scans and anisotropy of the induced current density (ACID) calculations, we showed that the B 2 NC 3 ‐ring in H is slightly aromatic [15] …”

“…Wagner's group and ours independently explored the BNB‐doped phenalenyl system H , wherein such steric stress is effectively prevented [14, 15] . Via in‐depth theoretical studies using nucleus‐independent chemical shift (NICS) scans and anisotropy of the induced current density (ACID) calculations, we showed that the B 2 NC 3 ‐ring in H is slightly aromatic [15] …”

“…Replacing one or more C=C pairs in mono‐ or polycyclic aromatic hydrocarbons (PAHs) by their isoelectronic and isosteric B=N units has brought about a wide range of novel heteroaromatic compounds, many of which show intriguing properties and functions [10, 11] . Surprisingly, PAHs comprising 3‐center 2‐π‐electron B‐N‐B moieties have been explored rather scarcely thus far [12–15] . Zeng et al.…”

“…[10,11] Surprisingly, PAHs comprising 3-center 2-pelectron B-N-B moieties have been explored rather scarcely thus far. [12][13][14][15] Zeng et al recently presented the BNB-phenalenyl analogue F. [12] Steric congestion between the two Bbonded phenyl groups causes significant distortion of its [3,2c:2',3'-e][1,2,7]azadiborepin (B), and dithieno [3,2-c:2',3'-e]-[1,2,7]oxadiborepin building blocks (C); the parent 1,2,7-azadiborepin (D) and borepin (E) ring systems; BNB-doped PAHs (F-H), and oxadiborepin-containing PAHs (I and J).…”