Carborane-stilbene dyads: the influence of substituents and cluster isomers on photoluminescence properties
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Publication date
2016
Authors
Juárez-Pérez, E. J.
Teixidor, F.
Pérez-Inestrosa, E.
Montenegro, J. M.
Sillanpää, R.
Haukkad, M.
Núñez, R.
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Publisher
Royal Society of Chemistry
Citation
Ferrer-Ugalde A, Cabrera-González J, Juárez-Pérez EJ, Teixidor F, Pérez-Inestrosa E, Montenegro JM, et al. Carborane–stilbene dyads: the influence of substituents and cluster isomers on photoluminescence properties. Dalton Trans 2017;46:2091–104. https://doi.org/10.1039/C6DT04003A.
Abstract
Two novel styrene-containing meta-carborane derivatives substituted at the second carbon cluster atom (Cc) with either a methyl (Me) or a phenyl (Ph) group are introduced herein along with a new set of stilbene-containing ortho- (o-) and meta- (m-) carborane dyads. The latter set of compounds have been prepared from styrene-containing carborane derivatives via a Heck coupling reaction. High regioselectivity has been achieved for these compounds by using a combination of palladium complexes [Pd2(dba)3]/[Pd(t-Bu3P)2] as a catalytic system, yielding exclusively E isomers. All compounds have been fully characterised and the crystal structures of seven of them were analysed by X-ray diffraction. The absorption spectra of these compounds are similar to those of their respective fluorophore groups (styrene or stilbene), showing a very small influence of the substituent (Me or Ph) linked to the second Cc atom or the cluster isomer (o- or m-). On the other hand, fluorescence spectroscopy revealed high emission intensities for Me-o-carborane derivatives, whereas their Ph-o-carborane analogues evidenced an almost total lack of fluorescence, confirming the significant role of the substituent bound to the adjacent Cc in o-carboranes. In contrast, all the m-carborane derivatives display similar photoluminescence (PL) behavior regardless of the substituent attached to the second Cc, demonstrating its small influence on emission properties. Additionally, m-carborane derivatives are significantly more fluorescent than their o-counterparts, reaching quantum yield values as high as 30.2%. Regarding solid state emission, only stilbene-containing Ph-o-carborane derivatives, which showed very low fluorescence in solution, exhibited notable PL emission in films attributed to aggregation-induced emission. DFT calculations were performed to successfully complement the photoluminescence studies, supporting the experimentally observed photophysical behavior of the styrene and stilbene-containing carborane derivatives. In conclusion, in this work it is proved that it is possible to tailor the PL properties of carborane-stilbene dyads by changing the Cc substituent and the carborane isomer.