DOI: 10.1002/chem.201302493 Synthesis, Characterization, and Thermal Behavior of Carboranyl–Styrene Decorated Octasilsesquioxanes: Influence of the Carborane Clusters on Photoluminescence Albert Ferrer-Ugalde, Emilio JosØ Juµrez-PØrez, Francesc Teixidor, Clara ViÇas, and Rosario NfflÇez* [a] Introduction Cubic silsesquioxanes (SSQs or POSS) are organic–inorgan- ic hybrid materials that consist of a nanometer-sized silox- ane cube (diameter ca. 0.5 nm) with eight Si atoms at the vertices, connected through O atoms along the edges, and can be functionalized by various organic pendant groups. POSS hydride can undergo hydrosilylation reactions with double bonds, whereas vinyl–POSS can undergo hydrosilyla- tion reactions with Si  H containing species, catalyzed by Pt 0 . Likewise, vinyl–POSS can be functionalized by hydro- bromination, Heck reactions, radical reactions, and more re- cently, by cross-metathesis, among others. [1] While the inor- ganic core provides mechanical stiffness and thermal stabili- ty, the pendant organic groups provide solubility in organic solvents and enable solution processing. Additionally, the in- troduction of different functional groups can enhance ther- mal stability and mechanical, optical, and electrical proper- ties. The interest in silsesquioxanes comes from the robust nature and ease of synthesis of these compounds, compared with that of more traditional organic molecules, [2] and also from the ability of these POSS compounds to be functional- ized for particular applications. [3] By varying the composi- tion and length of the pendant organic groups, one can tune the structure and properties of these POSS-based materials, which can be applied in a range of technologies, including hydrogen storage materials, encapsulants for drug delivery, porous media for trapping pollutants and other condensates, and functional coatings for scratch resistance or diffusion barriers. [4] Most recently, POSS derivatives have been used in electronic materials and in photonic materials as plat- forms for multiple components in organic light-emitting device (OLED) structures. [5] Abstract: Novel polyhedral oligomeric silsesquioxanes (POSS) or octasilses- quioxanes with carboranyl–styrene fragments attached to each corner are described. These compounds have been synthesized by olefin-metathesis reac- tions between octavinylsilsesquioxane and carboranyl–styrene compounds that possess different substituents (Ph, Me, or H). In all cases, these reactions, which were catalyzed by the Grubbs catalyst, are highly regioselective and yield exclusively the E isomers. The ex- istence of the carborane cage in the POSS structure induces a remarkable thermal stability in these compounds. After combustion at 1000 8C, these car- boranyl–POSS compounds exhibit a mass loss lower than 10%. The UV/ Vis absorption data of these carboran- yl–POSS compounds shows a slight bathochromic shift with respect to the carboranyl–styrene monomers, with an absorption maximum around 262 nm. Nevertheless, important differences in the emission spectra of the carboranyl– POSS compounds with regard to their carboranyl–styrene precursors are ob- served; the phenyl-o-carborane-con- taining POSS compound exhibits the highest fluorescence intensity (F F = 44 %), whereas for the POSS com- pound bearing the methyl substituent, and for the unsubstituted o-carborane clusters, the fluorescence intensity is much lower (F F = 9 and 2 %, respec- tively). This is precisely the reverse of what occurs with the monomers, in which the unsubstituted o-carboranyl– styrene compound exhibits the highest F F, and a quenching of the fluores- cence is observed in the phenyl-o-car- boranyl–styrene compound. In addi- tion, a large red shift of around 100 nm is observed for the POSS compounds with respect to their precursors. These experimental results can only be ac- counted for by the spatial ordering in- duced by the POSS core that eases in- teractions, which otherwise would not occur. These results have been con- firmed by time-dependent density func- tional theory (TDDFT) calculations that exclude a photoinduced electron transfer (PET) process in the POSS compounds. Keywords: boron cluster · carbor- anes · cluster compounds. · octasil- sesquioxanes · photoluminescence · styrene [a] A. Ferrer-Ugalde, E.J. Juµrez-PØrez, F. Teixidor, C. ViÇas, Dr. R. NfflÇez Institut de Cincia de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, 08193, Bellaterra (Barcelona) (Spain) Fax: (+ 34) 93-5805729 E-mail: rosario@icmab.es Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201302493. Chem. Eur. J. 2013, 19, 17021 – 17030  2013 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim 17021 FULL PAPER