Person:
Cabrera González, Justo Enrique

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First Name
Justo Enrique
Last Name
Cabrera González
URI
https://hdl.handle.net/20.500.14352/84486
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Químicas
Department
Química Orgánica
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2015 - 20203
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Author: Viñas, Clara × Item Type: Publication ×

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Now showing 1 - 3 of 3
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    High-Boron-Content Porphyrin-Cored Aryl Ether Dendrimers: Controlled Synthesis, Characterization, and Photophysical Properties
    (Inorganic Chemistry, 2015) Cabrera González, Justo Enrique; Xochitiotzi-Flores, Elba; Viñas, Clara; Teixidor, Francesc; García-Ortega, Héctor; Farfán, Noberto; Santillan, Rosa; Parella, Teodor; Núñez, Rosario
    The synthesis and characterization of a set of poly(aryl ether) dendrimers with tetraphenylporphyrin as the core and 4, 8, 16, or 32 closo-carborane clusters are described. A regioselective hydrosilylation reaction on the allyl-terminated functions with carboranylsilanes in the presence of Karstedt's catalyst leads to different generations of boron-enriched dendrimers. This versatile approach allows the incorporation of a large number of boron atoms in the dendrimers' periphery. Translational diffusion coefficients (D) determined by DOSY NMR experiments permit estimation of the hydrodynamic radius (RH) and molecular size for each dendrimer. Furthermore, a notable correlation between D and the molecular weight (MW) is found and can be used to predict their overall size and folding properties. The UV vis and emission behavior are not largely affected by the functionalization, therefore implying that the presence of carboranes does not alter their photoluminescence properties.
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    Photoluminescence in Carborane–Stilbene Triads: A Structural, Spectroscopic, and Computational Study
    (Chemistry - a European journal, 2016) Cabrera González, Justo Enrique; Viñas, Clara; Haukka, Matti; Bhattacharyya, Santanu; Gierschner, Johannes; Núñez, Rosario
    A set of triads in which o- and m-carborane clusters are bonded to two stilbene units through Ccluster−CH2 bonds was synthesized, and their structures were confirmed by X-ray diffraction. A study on the influence of the o- and m- isomers on the absorption and photoluminescence properties of the stilbene units in solution revealed no charge-transfer contributions in the lowest excited state, as confirmed by (TD)DFT calculations. The presence of one or two B−I groups in m-carborane derivatives does not affect the emission properties of the stilbenes in solution, probably due to the rather large distance between the iodo substituents and the fluorophore. Nevertheless, a significant redshift of the photoluminescence (PL) emission maximum in the solid state (thin films and powder samples) compared to solution was observed; this can be traced back to PL sensitization, most probably due to more densely packed stilbene moieties. Remarkably, the PL absolute quantum yields of powder samples are significantly higher than those in solution, and this was attributed to the restricted environment and the aforementioned sensitization. Thus, the bonding of the carborane clusters to two stilbene units preserves their PL behavior in solution, but produces significant changes in the solid state. Furthermore, iodinated species can be considered to be promising precursors for theranostic agents in which both imaging and therapeutic functions could possibly be combined.
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    Blue Emitting Star-Shaped and Octasilsesquioxane-Based Polyanions Bearing Boron Clusters. Photophysical and Thermal Properties
    (Molecules, 2020) Cabrera González, Justo Enrique; Chaari, Mahdi; Teixidor, Francesc; Viñas, Clara; Núñez, Rosario
    High boron content systems were prepared by the peripheral functionalisation of 1,3,5-triphenylbenzene (TPB) and octavinylsilsesquioxane (OVS) with two different anionic boron clusters: closo-dodecaborate (B12) and cobaltabisdicarbollide (COSAN). TPB was successfully decorated with three cluster units by an oxonium ring-opening reaction, while OVS was bonded to eight clusters by catalysed metathesis cross-coupling. The resulting compounds were spectroscopically characterised, and their solution-state photophysical properties analysed. For TPB, the presence of COSAN dramatically quenches the fluorescence emission (λem = 369 nm; ΦF = 0.8%), while B12-substituted TPB shows an appreciable emission efficiency (λem = 394 nm; ΦF = 12.8%). For octasilsesquioxanes, the presence of either COSAN or B12 seems to be responsible for ∼80 nm bathochromic shift with respect to the core emission, but both cases show low emission fluorescence (ΦF = 1.4–1.8%). In addition, a remarkable improvement of the thermal stability of OVS was observed after its functionalisation with these boron clusters.