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A combined experimental and theoretical study on the isomers of 2,3,4,5-tetracarba-nido-hexaborane(6) derivatives and their photophysical properties

journal contribution
posted on 2023-06-08, 18:19 authored by Holger Braunschweig, Sundargopal Ghosh, J Oscar C Jimenez-Halla, Johannes H Klein, Christoph Lambert, Krzysztof Radacki, Andreas Steffen, Alfredo VargasAlfredo Vargas, Johannes Wahler
Building upon our ongoing studies on the high-yield synthetic route to 2,3,4,5-tetracarba-1,6-nido hexaborane derivative 5, we continue to explore the chemistry of this system to isolate a range of perphenylated C4B2-type carborane isomers. As a result, the photolysis of 5 for an elongated period yielded 6, which exhibits an intense luminescence upon excitation with a UV lamp (?ex = 366 nm). In contrast, the conversion of 5 under thermal conditions (microwave heating) generated the isomer 7, which does not show any luminescence. The structural disparity among the three isomers 5-7 is the position of the butadiene moiety with respect to the C4B2-carborane cage as deduced from single-crystal X-ray diffraction analyses. In an attempt to generate the classical structural motif of 5, an equimolar amount of KOtBu was added to a THF solution of 5, immediately providing the boratacyclopentadiene derivative 8 in good yield. The observed rearrangement reactions were further investigated by quantum chemical calculations in order to suggest a plausible reaction pathway. According to the DFT calculations, the energetically favored reaction mechanism most likely involves tricyclic transition states and classical intermediate structures. In addition, the fluorescence emission properties of 6 were investigated in solution as well as in the solid state.

History

Publication status

  • Published

Journal

Chemistry - A European Journal

ISSN

1521-3765

Publisher

WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Issue

1

Volume

21

Page range

210-218

Department affiliated with

  • Chemistry Publications

Full text available

  • No

Peer reviewed?

  • Yes

Legacy Posted Date

2014-10-29

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