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

• Published in: Journal of the American Chemical Society Vol. 142; no. 25; pp. 11072 - 11083
• Main Authors: Scholz, Alexander S, Massoth, Julian G, Bursch, Markus, Mewes, Jan-M, Hetzke, Thilo, Wolf, Bernd, Bolte, Michael, Lerner, Hans-Wolfram, Grimme, Stefan, Wagner, Matthias
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 24.06.2020; Amer Chemical Soc
• Subjects: anhydrides; aromatic amines; boronic acids; chemical bonding; chemical reduction; Chemistry; Chemistry, Multidisciplinary; electron paramagnetic resonance spectroscopy; luminescence; Physical Sciences; polycyclic aromatic hydrocarbons; potassium; Science & Technology; PHYSICAL-PROPERTIES; B-N; ANALOGS; HOST MATERIALS; C-C; OPTICAL-PROPERTIES; CHEMISTRY; GRAPHENE; BORON-NITRIDE; CRYSTAL
• ISSN: 0002-7863; 1520-5126; 1520-5126
• DOI: 10.1021/jacs.0c03118

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].