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Issue 30, 2013
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C,C′-Bis(benzodiazaborolyl)dicarba-closo-dodecaboranes: Synthesis, structures, photophysics and electrochemistry

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Abstract

Six new C,C′-bis(benzodiazaborolyl)dicarba-closo-dodecaboranes, 1,A-R2-1,A-C2B10H10, where R represents the group 2-(1,3-Et2-1,3,2-N2BC6H4) or 2-(1,3-Ph2-1,3,2-N2BC6H4) and A is 2, 7 or 12, were synthesized from o-, m-, and p-dicarbadodecaboranes (carboranes) by lithiation and subsequent treatment with the respective 2-bromo-1,3,2-benzodiazaboroles. UV-visible and fluorescence spectra of all carboranes display low energy charge transfer emissions. While such emissions with Stokes shifts between 17 330 and 21 290 cm−1 are typical for C,C′-bis(aryl)-ortho-carboranes, the observed low-energy emissions with Stokes shifts between 8320 and 15 170 cm−1 for the meta- and para-isomers are unusual as high-energy emissions are typical for meta- and para-dicarbadodecaboranes. Fluorescence quantum yields (ϕF) for the novel 1,7- and 1,12-bis(benzodiazaborolyl)-carboranes depend on the substituents at the nitrogen atoms of the heterocycle. Thus, the para-carborane with N-ethyl substituents 1,12-(1′,3′-Et2-1′,3′,2′-N2BC6H4)2-1,12-C2B10H10 has a ϕF value of 41% in cyclohexane solution and only of 9% in the solid state, whereas the analogous 1,12-(1′,3′-Ph2-1′,3′,2′-N2BC6H4)2-1,12-C2B10H10 shows quantum yields of 3% in cyclohexane solution and 72% in the solid state. X-ray crystallographic, computational and cyclic voltammetry studies for these carboranes are also presented.

Graphical abstract: C,C′-Bis(benzodiazaborolyl)dicarba-closo-dodecaboranes: Synthesis, structures, photophysics and electrochemistry

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Publication details

The article was received on 06 May 2013, accepted on 05 Jun 2013 and first published on 24 Jun 2013


Article type: Paper
DOI: 10.1039/C3DT51125A
Citation: Dalton Trans., 2013,42, 10982-10996

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    C,C′-Bis(benzodiazaborolyl)dicarba-closo-dodecaboranes: Synthesis, structures, photophysics and electrochemistry

    L. Weber, J. Kahlert, R. Brockhinke, L. Böhling, J. Halama, A. Brockhinke, H. Stammler, B. Neumann, C. Nervi, R. A. Harder and M. A. Fox, Dalton Trans., 2013, 42, 10982
    DOI: 10.1039/C3DT51125A

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