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

Weber, L.; Kahlert, J.; Brockhinke, R.; Böhling, L.; Halama, J.; Brockhinke, A.; Stammler, H.-J.; Neumann, B.; Nervi, C.; Harder, R.A.; Fox, M.A.

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 17330 and 21290 cm−1 are typical for C,C′-bis(aryl)-ortho-carboranes, the observed low-energy emissions with Stokes shifts between 8320 and 15170 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.

Citation

Weber, L., Kahlert, J., Brockhinke, R., Böhling, L., Halama, J., Brockhinke, A., …Fox, M. (2013). C,C′-Bis(benzodiazaborolyl)dicarba-closo-dodecaboranes: Synthesis, structures, photophysics and electrochemistry. Dalton Transactions, 42(30), 10982-10996. https://doi.org/10.1039/c3dt51125a

• Journal Article Type: Article
• Acceptance Date: Jun 5, 2013
• Publication Date: Aug 14, 2013
• Deposit Date: May 27, 2014
• Publicly Available Date: Jul 15, 2014
• Journal: Dalton Transactions
• Print ISSN: 1477-9226
• Electronic ISSN: 1477-9234
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 42
• Issue: 30
• Pages: 10982-10996
• DOI: https://doi.org/10.1039/c3dt51125a
• Public URL: https://durham-repository.worktribe.com/output/1431007