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

Braunschweig, Holger, Ghosh, Sundargopal, Jimenez-Halla, J Oscar C, Klein, Johannes H, Lambert, Christoph, Radacki, Krzysztof, Steffen, Andreas, Vargas, Alfredo and Wahler, Johannes (2015) A combined experimental and theoretical study on the isomers of 2,3,4,5-tetracarba-nido-hexaborane(6) derivatives and their photophysical properties. Chemistry - A European Journal, 21 (1). pp. 210-218. ISSN 1521-3765

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Abstract

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 (λex = 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.

Item Type: Article
Schools and Departments: School of Life Sciences > Chemistry
Subjects: Q Science > QD Chemistry
Depositing User: Alfredo Vargas
Date Deposited: 29 Oct 2014 17:20
Last Modified: 19 Feb 2015 15:28
URI: http://sro.sussex.ac.uk/id/eprint/49945
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