Investigación

URI permanente para esta comunidadhttps://hdl.handle.net/11441/10690

Esta comunidad enfocada en la investigación recoge artículos, capítulos de libros, libros, ponencias y datos fuentes de investigación.

This research-focused community collects articles, book chapters, books, presentations and research source data.

Examinar

Mostrando 1 - 8 de 8

A Dynamic Kinetic Asymmetric Heck Reaction for the Simultaneous Generation of Central and Axial Chirality
(American Chemical Society, 2018) Carmona, José A.; Hornillos, Valentín; Ramírez López, Pedro; Ros Lao, Abel; Iglesias Sigüenza, Francisco Javier; Gómez-Bengoa, Enrique; Fernández Fernández, Rosario Fátima; Lassaletta Simón, José María; Universidad de Sevilla. Departamento de Química orgánica
A highly diastereo- and enantioselective, scalable Pd-catalyzed dynamic kinetic asymmetric Heck reaction of heterobiaryl sulfonates with electron-rich olefins is described. The coupling of 2,3-dihydrofuran or N-boc protected 2,3-dihydropyrrole with a variety of quinoline, quinazoline, phthalazine, and picoline derivatives takes place with simultaneous installation of central and axial chirality, reaching excellent diastereo- and enantiomeric excesses when in situ formed [Pd0/DM-BINAP] was used as the catalyst, with loadings reduced down to 2 mol % in large scale reactions. The coupling of acyclic, electron-rich alkenes can also be performed using a [Pd0/Josiphos ligand] to obtain axially chiral heterobiaryl α-substituted alkenes in high yields and enantioselectivities. Products from Boc-protected 2,3-dihydropyrrole can be easily transformed into N,N ligands or appealing axially chiral, bifunctional proline-type organocatalysts. Computational studies suggest that a β-hydride elimination is the stereocontrolling step, in agreement with the observed stereochemical outcome of the reaction.
A New Microchip Design. A Versatile Combination of Electromembrane Extraction and Liquid-Phase Microextraction in a Single Chip Device
(American Chemical Society, 2018-08-09) Ramos Payán, María Dolores; Santigosa, Elia; Fernández Torres, Rut; Bello López, Miguel Ángel; Universidad de Sevilla. Departamento de Química Analítica; Ministerio de Educación y Ciencia (MEC). España
For thefirst time, a novel and versatile microfluidic device wasdeveloped to achieve the possibility of combining different extraction principlesusing a miniaturized approach for the extraction of different classes of analytes.This novel microchip is composed of a sandwich of three poly(methylmethacrylate) (PMMA) layers. Four channels allowed the combination ofelectromembrane extraction (EME) and liquid-phase microextraction (LPME) inthree different ways: (I) EME and LPME, (II) EME and EME, or (III) LPME andLPME. The microchip can be used either (a) using a common acceptor phase (forboth extractions) for the simultaneous extraction of drugs from different nature in asingle step, or (b) a common sample solution (for both extractions) and twoacceptor solutions for simultaneous drug separation. In this work, the performanceof this novel microchip was demonstrated by simultaneous integration of EME andLPME using a common acceptor phase for both extractions. This configurationreduces the time of analysis allowing direct analysis in a single chip. The microchip was tested for extracting two different classesof analytes:fivefluoroquinolones and four parabens as model analytes. All effective variables were optimized for EME andLPME. Under the optimized conditions, the reusable microchip enables simultaneousμ-EME/LPME with extractionefficiencies over 77% in only 8 min extraction and sample volume consumption lower than 40μL. The optimized procedure wassuccessfully applied to urine samples obtaining recoveries over 90% for all analytes.
Cobalt metal-organic framework based on layered double nanosheets for enhanced electrocatalytic water oxidation in neutral media
(American Chemical Society, 2020) Gutiérrez Tarriño, Silvia; Olloqui Sariego, José Luis; Calvente Pacheco, Juan José; Mínguez Espallargas, Guillermo; Rey, Fernando; Corma, Avelino; Oña Burgos, Pascual; Universidad de Sevilla. Departamento de Química Física
A new cobalt metal-organic framework (2D-Co-MOF) based on well-defined layered double cores that are strongly connected by intermolecular bonds has been developed. Its 3D structure is held together by π-π stacking interactions between the labile pyridine ligands of the nanosheets. In aqueous solution, the axial pyridine ligands are exchanged by water molecules, producing a delamination of the material, where the individual double nanosheets preserve their structure. The original 3D layered structure can be restored by a solvothermal process with pyridine, so that the material shows a "memory effect"during the delamination-pillarization process. Electrochemical activation of a 2D-Co-MOF@Nafion-modified graphite electrode in aqueous solution improves the ionic migration and electron transfer across the film and promotes the formation of the electrocatalytically active cobalt species for the oxygen evolution reaction (OER). The so-activated 2D-Co-MOF@Nafion composite exhibits an outstanding electrocatalytic performance for the OER at neutral pH, with a TOF value (0.034 s-1 at an overpotential of 400 mV) and robustness superior to those reported for similar electrocatalysts under similar conditions. The particular topology of the delaminated nanosheets, with quite distant cobalt centers, precludes the direct coupling between the electrocatalytically active centers of the same sheet. On the other hand, the increase in ionic migration across the film during the electrochemical activation stage rules out the intersheet coupling between active cobalt centers, as this scenario would impair electrolyte permeation. Altogether, the most plausible mechanism for the O-O bond formation is the water nucleophilic attack to single Co(IV)-oxo or Co(III)-oxyl centers. Its high electrochemical efficiency suggests that the presence of nitrogen-containing aromatic equatorial ligands facilitates the water nucleophilic attack, as in the case of the highly efficient cobalt porphyrins.
Dynamic Kinetic Resolution of Hetero biaryl Ketones by Zinc- Catalyzed Asymmetr ic Hydrosil ylation
(Wiley, 2018) Hornillos, Valentín; Carmona, José A.; Ros Lao, Abel; Iglesias Sigüenza, Francisco Javier; López Serrano, Joaquín; Fernández Fernández, Rosario Fátima; Lassaletta, José M.; Universidad de Sevilla. Departamento de Química orgánica; Universidad de Sevilla. Departamento de Química Inorgánica
Adiastereo- and highly enantioselective dynamic kinetic resolution (DKR) of configurationally labile hetero- biaryl ketones is described. The DKR proceeds by zinc- catalyze dhydrosilylation of the carbonyl group ,thus leading to secondary alcohols bearing axial and central chirality .The strategy relies on the labilization of the stereogenic axis that takes place thanks to aLewis acid–base interaction between anitrogen atom in the heterocycle and the ketone carbonyl group .The synthetic utility of the methodology is demonstrated through stereospecific transformations into either N,N-ligands or appealing axially chiral, bifunctional thiourea organocata- lysts.
Enantio- and Diastereoselective Nucleophilic Addition of N-tert-Butylhydrazones to Isoquinolinium Ions through Anion-Binding Catalysis
(Wiley-Blackwell, 2021) Matador Martínez, Esteban; Iglesias Sigüenza, Francisco Javier; Monge Fernández, David; Merino, Pedro; Fernández Fernández, Rosario Fátima; Lassaletta, J. M.; Universidad de Sevilla. Departamento de Química orgánica; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; Gobierno de Aragón; Junta de Andalucía
A highly enantio- and diastereoselective thiourea-catalyzed dearomatization of isoquinolines employing N-tert-butylhydrazones as neutral α-azo carbanions and masked acyl anion equivalents has been developed. Experimental and computational data supports the generation of highly ordered complexes wherein the chloride behaves as a template for the catalyst, the hydrazone reagent, and the isoquinolinium cation, providing excellent stereocontrol in the formation of two contiguous stereogenic centers. The ensuing selective and high-yielding transformations provide appealing dihydroisoquinoline derivatives.
Spin-state-dependent electrical conductivity in single-walled carbon nanotubes encapsulating spin-crossover molecules
(Springer Nature, 2021) Villalva, Julia; Develioglu, Aysegul; Montenegro Pohlhammer, Nicolás; Sánchez de Armas, María Rocío; Gamonal, Arturo; Rial, Eduardo; García Hernández, Mar; Ruiz González, Luisa; Sánchez Costa, José; Jiménez Calzado, Carmen; Pérez, Emilio M.; Burzuri, Enrique; Universidad de Sevilla. Departamento de Química Física; Marie Skłodowska-Curie Actions (MSCA); Programa de Atracción del Talento Investigador. Comunidad de Madrid; Ministerio de Economia, Industria y Competitividad (MINECO). España; Consejo Europeo de Investigación (ERC); Comunidad Autónoma de Madrid; NANOMAGCOST
Spin crossover (SCO) molecules are promising nanoscale magnetic switches due to their ability to modify their spin state under several stimuli. However, SCO systems face several bottlenecks when downscaling into nanoscale spintronic devices: their instability at the nanoscale, their insulating character and the lack of control when positioning nanocrystals in nanodevices. Here we show the encapsulation of robust Fe-based SCO molecules within the 1D cavities of single-walled carbon nanotubes (SWCNT). We find that the SCO mechanism endures encapsulation and positioning of individual heterostructures in nanoscale transistors. The SCO switch in the guest molecules triggers a large conductance bistability through the host SWCNT. Moreover, the SCO transition shifts to higher temperatures and displays hysteresis cycles, and thus memory effect, not present in crystalline samples. Our results demonstrate how encapsulation in SWCNTs provides the backbone for the readout and positioning of SCO molecules into nanodevices, and can also help to tune their magnetic properties at the nanoscale.
Targeted and untargeted metabolomic analysis of Procambarus clarkii exposed to a “chemical cocktail” of heavy metals and diclofenac
(Elsevier, 2022-04) Rodríguez-Moro, Gema; Román Hidalgo, Cristina; Ramírez-Acosta, Sara; Aranda Merino, Noemí; Gómez Ariza, José Luis; Abril Díaz, Nieves; Bello López, Miguel Ángel; Fernández Torres, Rut; García Barrera, Tamara; Universidad de Sevilla. Departamento de Química Analítica; Universidad de Sevilla. FQM291: Análisis Químico; Universidad de Sevilla. FQM-141 Análisis Medioambiental y Bioanálisis
Water pollution poses an important problem, but limited information is available about the joined effects of xenobiotics of different chemical groups to evaluate the real biological response. Procambarus clarkii (P. clarkii) has been demonstrated to be a good bioindicator for assessing the quality of aquatic ecosystems. In this work, we studied the bioaccumulation of cadmium (Cd), arsenic (As) and diclofenac (DCF) in different tissues of P. clarkii during 21 days after the exposure to a “chemical cocktail” of As, Cd and DCF, and until 28 days considering a depuration period. In addition, a combined untargeted and targeted metabolomic analysis was carried out to delve the metabolic impairments caused as well as the metabolization of DCF. Our results indicate that As and Cd were mainly accumulated in the hepatopancreas followed by gills and finally abdominal muscle. As and Cd show a general trend to increase the concentration throughout the exposure experience, while a decrease in the concentration of these elements is observed after 7 days of the depuration process. This is also the case in the abdominal muscle for Cd, but not for As and DCF, which increased the concentration in this tissue in the depuration phase. The hepatopancreas showed the greatest number of metabolic pathways affected. Thus, we observed a crucial bioaccumulation of xenobiotics and impairments of metabolites in different tissues. This is the first study combining the exposure to metals and pharmaceutically active compounds in P. clarkii by untargeted metabolomics including the biotransformation of DCF.
Unraveling the role of chemical composition in the lattice thermal conductivity of oxychalcogenides as thermoelectric materials
(Royal Society of Chemistry, 2022-06) Blancas, Ernesto J.; Plata Ramos, José Javier; Santana, Julia; Lemus Prieto, Felipe; Márquez Cruz, Antonio Marcial; Fernández Sanz, Javier; Universidad de Sevilla. Departamento de Química Física; Ministerio de Ciencia e Innovación (MICIN). España; Red Española de Supercomputación (RES); Fundación Computación y Tecnologías Avanzadas de Extremadura (COMPUTAEX)
Oxychalcogenides represent a large chemical space with potential application as thermoelectric materials due to their low thermal conductivity. However, the nature of this behaviour is still under debate. Understanding the origin of the anharmonicity of these materials is key to developing models that improves the efficiency of thermoelectric materials. In this work, we combine machine learning with first principles calculations to explore oxychalcogenides materials. Machine learning not only accelerates the prediction of the lattice thermal conductivity for large chemical spaces with high accuracy, but also catalyzes the development of design principles to discover new thermoelectric materials. Using this approach, lattice thermal conductivity has been directly connected to the effect of each species in the material, using atomic projections of the scattering rates. The role of the monovalent atom and the lone pair electron for the trivalent cation are discussed in detail. Based on this knowledge, it is possible to connect complex properties such as lattice thermal conductivity with a more manageable synthetic variable such as chemical composition. Using this strategy, we propose promising new oxychalcogenides such as BiOAgSe, which subsequently has been confirmed as having ultra-low lattice thermal conductivity and BiOAg0.5Cu0.5Se which presents a lower κl and promising properties for thermoelectricity.

Examinar

Examinando Investigación por Premio "Premio Anual Publicación Científica Destacada de la US. Facultad de Química"