PUB - Publikationen an der Universität Bielefeld

The reaction of the N-lithiated 3,6-di-tert-butylcarbazole with fluorodimesitylborane afforded the N-carbazolyl-functionalized dimesitylborane 1 as a colorless solid in 70% yield. [4-(3,6-Di-tert-butylcarbazol-9-yl) phenyl]dimesitylborane (2) was synthesized in 59% yield by the lithiation of N-(4-bromophenyl)-3,6-di-tert-butylcarbazole and the subsequent treatment of the organolithium compound with fluorodimesitylborane. Synthesis of yellow crystalline [5-(carbazol-9-yl)-2-thienyl]dimesitylborane 3 was effected in 66% yield by the lithiation of 3,6-di-tert-butyl-N-(2-thienyl)carbazole and the subsequent reaction with fluorodimesitylborane. Coupling of N-(4-bromophenyl)-3,6-di-tert-butylcarbazole and 2-bromo-1,3-diethyl-1,3,2-benzodiazaborole with magnesium metal in boiling THF in the presence of lithium chloride led to the formation of the functionalized benzodiazaborole 5 as a colorless solid in 68% yield. Compounds 1-3 and 5 were characterized by elemental analyses, IR and NMR spectroscopy ((1)H, (11)B, (13)C) and mass spectrometry. The molecular structures of 1 and 3 were elucidated by X-ray diffraction analyses. The borylated systems show intense blue luminescence. The spectroscopic results were reproduced by TD-DFT calculations at the [B3LYP/6-311G(d,p)] level of theory. Thus, it was discovered that the LUMOs of 1-3 are located on the vacant 2p(z) orbital of the boron atom with contributions of the pi* orbital of the phenyl (in 2) or thiophene (in 3) unit, whereas the HOMOs are mainly represented by the carbazolyl unit.