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Fluorescent carborane-vinylstilbene functionalised octasilsesquioxanes: synthesis, structural, thermal and photophysical properties

Abstract

A new set of four different fluorescent boron-rich hybrids based on an octasilsesquioxane core (T8) are presented herein. The syntheses have been carried out starting from styrene-containing ortho- and meta-carboranes and an adequately substituted octasilsesquixane derivative (p-BrStyrenylOS) via Heck coupling reaction. The carborane clusters are attached to the T8 core through para-substituted stilbene spacers, which act as the main electronic donor of the molecule and as a result are responsible for the photoluminescence properties of the hybrids. These have been assessed in DCM solution, concluding that the presence of the carborane clusters plays a key role in the increase of the fluorescence emission displayed by the hybrids. A comparative study of different substituents (H, Me or Ph) linked to the adjacent carbon atom of the ortho-cluster revealed that the unsubstituted o-carborane derivative (POSS-H) has a much higher quantum yield in solution (F = 59%) than its two counterparts. Besides, a comparison between two hybrids containing phenyl-substituted ortho- (POSS-Ph) and meta-carborane (POSS-mPh), demonstrated a significant higher emission enhancement by the latter, backing the results we have previously reported for similar systems. In solid state, the emission is largely quenched in all cases (F = 4 to 7%) as well as bathochromically shifted due to considerable intermolecular interactions. Finally, the thermal resistances of these hybrids were tested by TGA under inert atmosphere, unveiling weight losses as low as 15.8 % and proving that the attachment of the carborane moieties to the T8 core outstandingly improves the thermal stability of the final POSS.

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Publication details

The article was received on 24 Jul 2017, accepted on 09 Sep 2017 and first published on 12 Sep 2017


Article type: Paper
DOI: 10.1039/C7TC03319B
Citation: J. Mater. Chem. C, 2017, Accepted Manuscript
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    Fluorescent carborane-vinylstilbene functionalised octasilsesquioxanes: synthesis, structural, thermal and photophysical properties

    J. Cabrera-González, A. Ferrer‐Ugalde, S. Bhattacharyya, M. Chaari, F. Teixidor, J. Gierschner and R. Nunez, J. Mater. Chem. C, 2017, Accepted Manuscript , DOI: 10.1039/C7TC03319B

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