Person:
Cabrera González, Justo Enrique

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

Identifiers

Full item page

Search Results

Now showing 1 - 10 of 10

Highly Dispersible and Stable Anionic Boron Cluster-Graphene Oxide Nanohybrids
(Chemistry - A European Journal, 2016) Cabrera González, Justo Enrique
An efficient process to produce boron cluster-graphene oxide nanohybrids that are highly dispersible in water and organic solvents is established for the first time. Dispersions of these nanohybrid materials in water were extraordinarily stable after one month. Characterization of hybrids after grafting of appropriate cobaltabisdicarbollide and closo-dodecaborate derivatives onto the surface of graphene oxide (GO) was done by FT-IR, XPS, and UV/Vis. Thermogravimetric analysis (TGA) clearly shows a higher thermal stability for the modified-GO nanohybrids compared to the parent GO. Of particular note, elemental mapping by energy-filtered transmission electron microscopy (EFTEM) reveals that a uniform decoration of the graphene oxide surface with the boron clusters is achieved under the reported conditions. Therefore, the resulting nanohybrid systems show exceptional physico-chemical and thermal properties, paving the way for an enhanced processability and further expanding the range of application for graphene-based materials.
Redox-active metallacarborane-decorated octasilsesquioxanes. Electrochemical and thermal properties
(Inorganic Chemistry, 2016) Cabrera González, Justo Enrique; Sanchez-Arderiu, Víctor; Viñas, Clara; Parella, Teodor; Teixidor, Francesc; Nuñez, Rosario
Polyanionic and electroactive hybrids based on octasilsesquioxanes bearing metallacarborane units are developed. They show remarkable solubility in organic solvents and outstanding thermal stability. The metallacarboranes act as independent units simultaneously undergoing the reversible redox process.
Tetrakis{[(p-dodecacarboranyl)methyl]stilbenyl}ethylene:A Luminescent Tetraphenylethylene (TPE) Core System
(European Journal of Inorganic Chemistry, 2017) Cabrera González, Justo Enrique
The synthesis and spectroscopic characterization of the first set of tetrakis{[(p-dodecacarboranyl)methyl]stilbenyl}ethylenes (TDSE), substituted either with a methyl or a phenyl group in the 2-position (Ccluster) of the ortho-carborane, are described. The complex absorption properties are elucidated by TD-DFT calculations, stressing the importance of through-bond conjugation. Enhanced conjugation and restriction of the conformational space are identified as the main factors for boosted luminescence properties in solution, compared with the tetraphenylethylene (TPE) core, effectively reducing internal conversion (IC). IC is further reduced when aggregate suspensions of our compounds are formed in water, providing highly luminescent materials of quasi-isolated (very weakly interacting) emitters.
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.
Organotin dyes bearing anionic boron clusters as cell-staining fluorescent probes
(Chemistry – A European Journal, 2018) Cabrera González, Justo Enrique
Within the cell nucleus, in the nucleoli, ribosomal RNAs are synthesized and participate in several biological processes. To better understand nucleoli-related processes, their visualization is often required, for which specific markers are needed. Herein, we report the design of novel fluorescent organotin compounds derived from 4-hydroxy-N′-((2-hydroxynaphthalen-1-yl)methylene)benzohydrazide and their cytoplasm and nucleoli staining of B16F10 cells in vitro. Tin compounds bearing an aliphatic carbon chain (-C12H25) and an electron-donating group (-OH) were prepared, and the latter could be derivatized to bear the boron cluster anions [B12H12]2− and [3,3′-Co(1,2-C2B9H11)2]− (COSAN). All of the conjugates have been fully characterized and their luminescence properties have been assessed. In general, they show good quantum yields in solution (24–49 %), those for the COSAN derivatives being lower. Remarkably, the linking of [B12H12]2− and COSAN to the complexes made them more soluble, without being detrimental to their luminescence properties. Living B16F10 cells were treated with all of the compounds to determine their fluorescence staining properties; the compounds bearing the aliphatic chain showed a reduced staining capacity due to the formation of aggregates. Notably, the complexes bearing different boron clusters showed different staining effects; those bearing [B12H12]2− showed extraordinary staining of the nucleoli and cytoplasm, whereas those bearing COSAN were only detected in the cytoplasm. The remarkable fluorescence staining properties shown by these organotin compounds make them excellent candidates for fluorescence bioimaging in vitro.
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.
Multinuclear Ru(II) and Ir(III) decorated tetraphenylporphyrins as efficient PDT agents
(Biomaterials Science, 2019) Cabrera González, Justo Enrique
Two novel porphyrin-core systems were prepared by Sonogashira cross-coupling of the terminal alkyne groups of meso-tetra(4-ethynylphenyl)porphyrin-Zn(ii) (P-1) with halogenated Ru(ii)- or Ir(iii)-phenanthroline complexes. The resulting compounds (P-Ru and P-Ir) were spectroscopically characterised and their photophysical properties were investigated (λem 625, 665 nm; τT 339.6 μs (P-Ru) and λem 530, 612, 664 nm; τT 396.6 μs (P-Ir)). Nanosecond time-resolved transient absorption studies were used to explore the 3MLCT nature of the triplet excited states, and the singlet oxygen quantum yields were determined (ΦΔ 44.8 (P-Ru), 33.2 (P-Ir)%). The subcellular uptake of P-Ru and P-Ir and their application as photosensitisers (PS) in photodynamic therapy (PDT) were explored due to their solution photophysics and absence of dark toxicity. Upon irradiation (λexc = 620-630 nm; 10 min; 33 J cm-2), both P-Ru and P-Ir killed 90% of SKBR-3 cells at 1 μM. Notably P-Ru induced a 77% decrease in cell viability at only 0.25 μM.
Carborane-stilbene dyads: the influence of substituents and cluster isomers on photoluminescence properties
(Dalton Transactions, 2016) Cabrera González, Justo Enrique; Juárez-Pérez, E. J.; Teixidor, F.; Pérez-Inestrosa, E.; Montenegro, J. M.; Sillanpää, R.; Haukkad, M.; Núñez, R.
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.
Fluorescent carborane-vinylstilbene functionalised octasilsesquioxanes: Synthesis, structural, thermal and photophysical properties
(Journal of Materials Chemistry C, 2017) Cabrera González, Justo Enrique
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 (ΦF = 59%) than its two counterparts. Besides, a comparison between two hybrids containing phenyl-substituted ortho- (POSS-Ph) and meta-carborane (POSS-mPh), demonstrated a significantly higher emission enhancement by the latter, backing the results we have previously reported for similar systems. In the solid state, the emission is largely quenched in all cases (ΦF = 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 an 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.
Synthesis and self-assembly of a carboranecontaining ABC triblock terpolymer: morphology control on a dual-stimuli responsive system
(Polymer Chemistry, 2019) Fernáncez Alvarez, Roberto; Hlavatovicová, Eva; Rodzén, Krzysztof; Strachota, Adam; Kereïche, Sami; Matejicek, Pavel; Cabrera González, Justo Enrique; Núñez, Rosario; Uchman, Mariusz
Amphiphilic triblock terpolymers have attractive applications in the preparation of nanoparticles with controlled morphology. An additional level of morphology control can be provided by reactive blocks, whose interactions with the solvent vary under different stimuli. In this work, we synthesized a triblock terpolymer (poly(acrylic acid)-b-poly(4-hydroxystyrene)-b-poly{1-[4-(1-methyl-1,2-dicarba-closo-dodecaborane-2-yl methyl)-phenyl]ethylene}) (PAA-b-PHS-b-PSC) containing carboranes as pendant groups by reversible addition fragmentation chain transfer (RAFT) polymerization and subsequently studied its behavior in aqueous solution. Once the nanoparticles were formed, the solubility of the second and third blocks was changed via pH and CsF reactions, respectively. The resulting micelles work as an ON/OFF system, using changes in fluorescence intensity at different pH values.