BNB-Doped Phenalenyls: Modular Synthesis, Optoelectronic Properties, and One-Electron Reduction

Abstract

A highly modular synthesis of BNB- and BOB-doped phenalenyls is presented. Treatment of the 1,8-naphthalenediyl-bridged boronic acid anhydride 1 with LiAlH4/Me3SiCl afforded the corresponding 1,8-naphthalenediyl-supported diborane(6) 2, which served as the starting material for all subsequent transformations. Upon addition of MesMgBr/Me3SiCl, 2 was readily converted to the tetraorganyl diborane(6) 5. The further heteroatoms were finally introduced through the reaction of 2 with (Me3Si)2NR′ or 5 with H2NR′ or H2O (R′ = H, Me, p-Tol). A helically twisted, fully BNB-embedded PAH 11 was prepared by combining 2 with a dibrominated m-terphenylamine, followed by a Grignard-mediated double ring-closure reaction. All compounds devoid of B–H bonds show favorable optoelectronic properties, such as luminescence and reversible reduction behavior. In the case of the BNB-phenalenyl 7 (BMes, NMe), the radical-anion salt K­[7 •] was generated through chemical reduction with K metal and characterized by EPR spectroscopy. K­[7 •] is not long-term stable in a THF/c-hexane solution, but abstracts an H atom with formation of the diamagnetic BNB-doped 1H-phenalene K­[7H].

Switching between mono and doubly reduced odd alternant hydrocarbon: designing a redox catalyst

“…Furthermore, this observation of PLY ring dearomatization clearly indicates that the (-CH=CH-) alkene fragment of PLY transforms into alkane (-CH 2 -CH 2 -) fragment upon two electron reduction and addition of 2 H + (from HCl). It may be noted that hydrogen atom abstraction by mono-reduced B-N-B embedded PLY radical has been reported by Wagner and coworkers very recently 37 and the dearomatization of PLY radical by abstraction of a hydride (H + +2e -) has been demonstrated earlier 24 . Such conclusion was also supported by our isotope labelling experiment with DCl and by characterizing the deuterium incorporated product (see SI, Figures S17-21).…”

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)° ( 7 Tip ), respectively. The B−N bond lengths in 7 Tip are 1.434(5) and 1.445(5) Å, 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) Å) [12] and G (1.46 Å) [13] …”

“…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]…”

One tool to bring them all: Au-catalyzed synthesis of B,O- and B,N-doped PAHs from boronic and borinic acids

“…115 In contrast to the selective diborylation of 9, the corresponding reaction between carbonaceous perylene and 2.2 equiv. of B2pin2 furnished a mixture of mono-(11), di-(three isomers, 12a-c), tri-(13), and tetraborylated (14) products (Scheme 5). While the perylenes carrying different numbers of Bpin substituents have been separated by HPLC, it has been found impossible to separate 12a-c. On the other hand, the 2,5,8,11-tetraborylated perylene 14, which does not (yet) have a (B,O)2-analogue, was accessible in 83% yield by using 4.4 equiv.…”

“…2 By varying the positions, 3 orientations, and number of -B=N + units within the molecular framework, a greatly expanded structural and chemical space becomes accessible. [4][5][6][7][8][9][10][11][12][13][14][15] In addition, breaking the symmetry of a molecular scaffold through the introduction of a -B=N + unit often allows late-stage functionalizations with higher regioselectivities than in the case of the parent PAH. 16 Because of these appealing features, considerable research efforts are currently being made to develop novel B,N-PAHs.…”