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

A highly modular synthesis of BNB- and BOB-doped phenalenyls is presented. Treatment of the 1,8-naphthalenediyl-bridged boronic acid anhydride with LiAlH/MeSiCl afforded the corresponding 1,8-naphthalenediyl-supported diborane(6) , which served as the starting material for all subsequent transformations. Upon addition of MesMgBr/MeSiCl, was readily converted to the tetraorganyl diborane(6) . The further heteroatoms were finally introduced through the reaction of with (MeSi)NR' or with HNR' or HO (R' = H, Me, -Tol). A helically twisted, fully BNB-embedded PAH was prepared by combining with a dibrominated -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 (BMes, NMe), the radical-anion salt K[] was generated through chemical reduction with K metal and characterized by EPR spectroscopy. K[] is not long-term stable in a THF/-hexane solution, but abstracts an H atom with formation of the diamagnetic BNB-doped 1-phenalene K[H].