title: Carborane-stilbene dyads: the influence of substituents and cluster isomers on photoluminescence properties.
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 Ccatom 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 Ccin 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 Ccsubstituent and the carborane isomer.
authors.affiliation: Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus U.A.B., 08193, Bellaterra, Barcelona, Spain. rosario@icmab.es.
authors.forename: A
authors.initials: A
authors.lastname: Ferrer-Ugalde
authors.affiliation: Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus U.A.B., 08193, Bellaterra, Barcelona, Spain. rosario@icmab.es.
authors.forename: J
authors.initials: J
authors.lastname: Cabrera-González
authors.affiliation: Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus U.A.B., 08193, Bellaterra, Barcelona, Spain. rosario@icmab.es.
authors.forename: E J
authors.initials: EJ
authors.lastname: Juárez-Pérez
authors.affiliation: Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus U.A.B., 08193, Bellaterra, Barcelona, Spain. rosario@icmab.es.
authors.forename: F
authors.initials: F
authors.lastname: Teixidor
authors.affiliation: Universidad de Málaga, IBIMA, Department of Organic Chemistry, 29071-Malaga, Spain and Andalusian Centre for Nanomedicine and Biotechnology-BIONAND, Parque Tecnológico de Andalucía, 29590-Málaga, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Pérez-Inestrosa
authors.affiliation: Universidad de Málaga, IBIMA, Department of Organic Chemistry, 29071-Malaga, Spain and Andalusian Centre for Nanomedicine and Biotechnology-BIONAND, Parque Tecnológico de Andalucía, 29590-Málaga, Spain.
authors.forename: J M
authors.initials: JM
authors.lastname: Montenegro
authors.affiliation: Department of Chemistry, University of Jyväskylä, FIN-40014, Jyväskylä, Finland.
authors.forename: R
authors.identifier: http://orcid.org/0000-0003-4582-5148
authors.initials: R
authors.lastname: Sillanpää
authors.affiliation: Department of Chemistry, University of Jyväskylä, FIN-40014, Jyväskylä, Finland.
authors.forename: M
authors.initials: M
authors.lastname: Haukka
authors.affiliation: Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus U.A.B., 08193, Bellaterra, Barcelona, Spain. rosario@icmab.es.
authors.forename: R
authors.initials: R
authors.lastname: Núñez