PUB - Publikationen an der Universität Bielefeld

Reaction of 1,4-bis(dibromoboryl) benzene (1a) with 2 equiv. of the diazabutadiene (BuN)-Bu-t = CH - CH= (NBu)-Bu-t and subsequent reduction of the obtained bis(1,3,2-diazaborolium) salt 2a with sodium amalgam afforded the 1,4-bis(1,3,2-diazaborolyl) benzene 3a. Similary, 1,3-bis(dibromoboryl) benzene (1b), 1,3,5-tris(dibromoboryl) benzene (1c) and 4,4'-bis(dibromoboryl) biphenyl (1d) were converted into compounds 3b, 3c and 3d which contain two or three diazaborolyl substituents at the arene core. Treatment of precursors 1a, b, d with two equiv. or 1c with three equiv. of N,N'-di-tert-butylethane-1,2-diamine in the presence of an excess of NEt3 gave rise to the diazaborolidine derivatives 4a-4d. Reaction of 1,3-bis(diiodoboryl) benzene 1e with two equivalents of N,N'-dimethylethane-1,2-diamine in the presence of NEt3 furnished the corresponding 1,3-bis(diazaborolidinyl) benzene 4e. The novel compounds were characterized by elemental analyses and spectroscopy (H-1, C-13, B-11 NMR, MS). The molecular structures of 3c, 4a and 4e were eludicated by X-ray-diffraction analyses. In addition to this, the oxidative cyclovoltammograms and blue emission spectra of these novel compounds were discussed. Here, the electronic communication between boron heterocycles on the different spacer-units and the luminescence of the oligo-diazaborolylarenes were of interest.