Mostrando recursos 1 - 20 de 296

  1. Planarity vs. Non-Planarity in the Electronic Communication of TCAQ-Based Push-Pull Chromophores

    García, Raúl; Calbo, Joaquín; Viruela, Rafael; Herranz, Maria Ángeles; Ortí, Enrique; Martín, Nazario
    Donor-acceptor alkynes, endowed with 11,11,12,12-tetracyano-9,10-anthraquinodimethane (TCAQ) and N,N-dimethylaniline (DMA) units, have been further functionalized by a [2+2] tetracyanoethylene (TCNE) cycloaddition followed by a subsequent retroelectrocyclization to form distorted non-planar molecular structures with 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) bridge ligands. Comprehensive spectroscopic, electrochemical, and computational studies have been carried out to compare the electronic communication in these planar (alkyne) and nonplanar (with TCBD units) TCAQ-based push-pull chromophores. Cyclic voltammetry and UV-Vis absorption measurements confirm a noticeable electronic communication between the TCAQ and DMA units regardless the quasi-orthogonal arrangement of the two dicyanovinyl halves of the TCBD groups, which partially hinder the electronic communication. The...

  2. Química de polienos : desarrollo de nuevas estrategias sintéticas en tándem dirigidas a la obtención de scaffolds policíclicos

    Riveira, Martín Jorge
    Las reacciones dominó constituyen una rama fascinante de la química orgánica. Estas han sido definidas como procesos en los que están involucrados dos o más transformaciones de formación o fragmentación de enlaces, que ocurren bajo las mismas condiciones de reacción, sin el agregado de reactivos o catalizadores, y en los cuales cada etapa de reacción es consecuencia directa de la funcionalidad creada en la anterior. Esencialmente, las reacciones dominó generan complejidad molecular de manera eficiente, son simples, selectivas y por sobre todo, la principal ventaja en su empleo se relaciona con la gran reducción de costos y efectos adversos sobre...

  3. Impacto de reacciones de halogenación sobre la composición y las actividades biológicas de mezclas complejas naturales

    García, Paula
    Un paso limitante en la búsqueda de nuevas drogas es el acceso a bibliotecas de compuestos con propiedades biológicas interesantes. Los productos naturales (PNs) han sido muy valiosos como plataforma validada biológicamente por contener esqueletos moleculares que presentan dichas cualidades. Una metodología que utiliza a los PNs como punto de partida para la generación de compuestos con potencial actividad biológica es la Diversificación Química de Extractos. La misma apunta a producir cambios en las estructuras químicas de los componentes de extractos naturales a través de reacciones químicas seleccionadas. Estos cambios consisten en la introducción de grupos funcionales o de elementos atípicamente...

  4. Unique pharmacological properties of serotoninergic G-protein coupled receptors from cestodes

    Camicia, Federico; Celentano, Ana M.; Johns, Malcolm E.; Chan, John D.; Maldonado, Lucas; Vaca, Hugo; Siervi, Nicolás Di; Kamenetzky, Laura; Gamo Albero, Ana María; Ortega Gutiérrez, Silvia; Martín Fontecha, María del Mar; Davio, Carlos; Marchant, Jonathan S.; Rosenzvit, Mara C.
    Background: Cestodes are a diverse group of parasites, some of them being agents of neglected diseases. In cestodes, little is known about the functional properties of G protein coupled receptors (GPCRs) which have proved to be highly druggable targets in other organisms. Notably, serotoninergic G-protein coupled receptors (5-HT GPCRs) play major roles in key functions like movement, development and reproduction in parasites. Methodology/Principal findings: Three 5-HT GPCRs from Echinococcus granulosus and Mesocestoides corti were cloned, sequenced, bioinformatically analyzed and functionally characterized. Multiple sequence alignment with other GPCRs showed the presence of seven transmembrane segments and conserved motifs but interesting differences were...

  5. Heterogeneous catalysis: understanding the fundamentals for catalyst design

    Corma Canós, Avelino
    [EN] Taking the chemoselective hydrogenation of substituted nitroaromatics as a base case, it will be shown that it is possible to design improved and new catalysts by attacking the problem in a multidisciplinary way. By combining molecular modeling with in situ operando spectroscopy, and with micro-kinetic and isotopic studies, it is possible to determine how and where on the catalysts the reactant molecules interact. Then, materials synthesis methods can be applied to prepare catalysts with the desired surface active sites and their selective interaction with the reactants.

  6. Autoria criativa: explorando jogos por meio de atividades autônomas na elaboração conceitual em química orgânica no ensino médio

    Scholl, Felipe Elemar
    Este trabalho se propõe a analisar a criatividade estimulada pela produção autoral. Para atingir tal propósito, empregou-se uma Unidade de Aprendizagem, como método alternativo ao ensino tradicional, relacionada ao conteúdo de funções orgânicas. Teve por público-alvo duas turmas de terceiro ano do ensino médio de uma escola da região metropolitana da capital do Rio Grande do Sul. Para que esse objetivo fosse atingido, a investigação foi desempenhada seguindo o fio norteador da Unidade de Aprendizagem, possibilitando o encadeamento dos conteúdos e conceitos, dentro da qual foram empregados jogos em sala de aula. Foram criados alguns jogos envolvendo compostos orgânicos. Analisam-se...

  7. Experiencia en el uso del aula virtual para el proceso de enseñanza y aprendizaje de sustitución por radicales libres

    Ferrer, Liliana; Videla, María S.; Ohanian, Gabriela; Sebök, Alejandra
    Es indiscutible que estamos asistiendo a un cambio sustancial en la manera en que el estudiante construye el saber y los docentes debemos ser partícipes de esa construcción. El aprendizaje centrado en la actividad del alumno y el empleo de las nuevas tecnologías de información y comunicación son los dos ejes del mejoramiento de la calidad de la enseñanza universitaria actual. Se presenta una experiencia de uso de TIC cuyo objetivo es lograr que los estudiantes mejoren su rendimiento académico mediante una propuesta que promueve el aprendizaje significativo del contenido Sustitución por Radicales Libres, en la asignatura Química Orgánica de...

  8. Multinuclear silver(I) XPhos complexes with cyclooctatetraene: photochemical C-C bond cleavage of acetonitrile and cyanide bridged Ag cluster formation

    Grirrane ., Abdessamad; Alvarez-González, Eleuterio; Albero-Sancho, Josep; García Gómez, Hermenegildo; Corma Canós, Avelino
    [EN] Cationic mono-, di-, tri-and tetra-nuclear silver complexes with Buchwald-type phosphane (XPhos) and cyclooctatetraene (COT) have been synthesized and characterized. Formation of [(XPhos-Ag) n(COT)][SbF6](n) (n = 1 and 2) complexes was confirmed by single-crystal X-ray crystallography and multinuclear NMR spectroscopy. Variable-temperature NMR spectroscopy in CD2Cl2 solution shows the fluxionality of the COT ring in the mono-Ag(I) XPhos complex. Fluxionality of COT was also confirmed in the case of the di-Ag(I) XPhos complex by solid-state and solution P-31 NMR spectroscopy. The C-C bond cleavage of coordinated acetonitrile [XPhos-Ag(I)-NCCH3] resulting in cyanide bridged Ag cluster formation [(XPhos-Ag)(2)(mu-CN)(n)(mu-Ag)(n-1)] (n = 1, 2, 3...

  9. Grafenos como carbocatalizadores y soporte de nanopartículas metálicas orientadas.

    Esteve Adell, Iván
    A lo largo de los últimos años, el grafeno ha despertado un gran interés entre la comunidad científica debido las numerosas aplicaciones que ha encontrado dentro del campo de las industrias electrónica, informática y automovilística, así como en ciencia de los materiales. Dadas las extraordinarias propiedades físico-químicas que presenta el grafeno, se pueden desarrollar materiales con altas conductividades y durezas, además de propiedades interesantes en muchos campos de investigación. El empleo de grafeno como soporte o como catalizador sostenible libre de metales, está siendo un tema de interés en muchos grupos de investigación actualmente. Teniendo en cuenta la tendencia al...

  10. La Química Verde, ¿una herramienta para enfrentar los problemas ambientales? Análisis de sus propuestas y bases teórico-epistemológicas a través de las publicaciones científicas

    Huergo, Juliana
    A partir de la consideración del Ambiente como un Sistema Complejo, cualquier intento de abordar la crisis ambiental en la que se encuentra nuestro planeta debe partir de diálogos de saberes, no sólo disciplinares sino también populares, acordando en posicionamientos éticos. Por esta razón, en este trabajo de tesis nos proponemos realizar un estudio para intentar discernir si la Química Verde, como propuesta científica, se aboca a la resolución de los problemas ambientales desde esta perspectiva. El objetivo general es describir la evolución de dicha propuesta en el período que va desde 2008 a 2015 y caracterizar su discurso a...

  11. Tratamento de efluentes da indústria de conservas de peixe por coagulação-floculação com diferentes coagulantes

    Cristovão, Raquel; Martins, Ramiro; Loureiro, José; Boaventura, Rui
    Os principais problemas ambientais das indústrias de conservas de peixe são o elevado consumo de água e o elevado conteúdo de matéria orgânica, óleos e gorduras e sais nos seus efluentes. Cada vez mais há uma necessidade de se considerar o tratamento deste tipo de efluentes de forma a que estes cumpram os requisitos de qualidade ditados pela legislação. Assim, este trabalho tem como objectivo o estudo do tratamento primário de efluentes da indústria de conservas de peixe através de um tratamento por coagulação-floculação química. Para tal, testaram-se quatro coagulantes diferentes (um orgânico e três inorgânicos) e várias concentrações de cada um deles (100, 200 e 400 mg/L), de forma a...

  12. Synthesis and structure of polymorph B of zeolite Beta

    Corma Canós, Avelino; Moliner Marin, Manuel; Cantin Sanz, Angel; Díaz Cabañas, Mª José; Jorda Moret, Jose Luis; Zhang, Daliang; Sun, Junliang; Jansson, Kjell; Hovmoller, Sven; Zou, Xiaodong
    [EN] It was found that either polymorph B or polymorph C of zeolite beta can be obtained from the same structure directing agent: 4,4-dimethyl-4-azonia-tricyclo[5.2.2.0(2,6)] undec-8-ene hydroxide. The synthesis occurs through a consecutive process where polymorph B is first formed and then transformed into polymorph C. It is possible to produce a zeolite highly enriched in polymorph B, provided that the transformation of this phase into polymorph C is slowed down up to the point where polymorph C is only detected at trace levels. The structure of polymorph B was determined for the first time by electron crystallography with SAED and...

  13. Sustainability integration in luxury fashion supply chains : An empirical investigation of leather and textiles in Italy

    Karaosman, Hakan
    La presente tesis doctoral explora en qué medida las sostenibilidades ambiental y social se integran en las cadenas de suministro de las marcas de moda de lujo que producen textiles (ropa) y zapatos de cuero en Italia. En primer lugar, se realizó una revisión sistemática de la literatura para categorizar las prácticas de sostenibilidad ambiental y social implementadas en las operaciones de moda y abordadas en la literatura existente. Posteriormente, desde un punto de vista de resource-based view o visión basada en recursos naturales, se optó por un método de estudio de casos múltiples al cubrir diez empresas ubicadas en...

  14. High-silica nanocrystalline Beta zeolites: efficient synthesis and catalytic application

    Martinez Franco, Raquel; Paris-Carrizo, Cecilia Gertrudis; MARTÍNEZ ARMERO, MARTA EVELIA; Martínez, Cristina; Moliner Marin, Manuel; Corma Canós, Avelino
    [EN] An efficient synthesis methodology to obtain homogeneous nanosized high-silica Beta zeolites ( 10¿20 nm) with high solid yields (above 95%) using simple alkyl-substituted flexible dicationic OSDAs is described. These dicationic OSDAs allow the synthesis of nanosized Beta zeolites with different Si/Al ratios (15¿30) in alkaline and fluoride media, resulting in nanocrystalline materials with different physicochemical properties. These nanosized Beta zeolites show better catalytic behavior towards the industrially-relevant alkylation of benzene with propylene to obtain cumene compared with other commercially available nanosized Beta zeolites.

  15. Valoursul SA - Estação de Tratamento e Valorização Orgânica

    Cardoso, Joaquim Carlos Balasteiro
    No âmbito da dissertação de Mestrado, tendo tido a opção e possibilidade de tal., foi realizado um estágio curricular, tendo uma duração de um ano curricular, cerca de 1500 horas. O estágio foi realizado na Empresa Valorsul – Valorização e Tratamento de Resíduos Sólidos das Regiões de Lisboa e do Oeste, sendo a empresa responsável pelo tratamento e valorização das cerca de 950 mil toneladas de resíduos urbanos produzidos, por ano, em 19 Municípios da Grande Lisboa e da Região Oeste. O estágio foi realizado numa das Unidades da Empresa – Estação de Tratamento e Valorização Orgânica (ETVO), sita na Serra...

  16. Multivalent Glycosylated Nanostructures for Ebola Virus Infection

    Illescas, Beatriz M.; Rojo, Javier; Delgado, Rafael; Martín, Nazario
    The infection of humans by lethal pathogens such as Ebola and other related viruses has not been properly addressed so far. In this context, a relevant question arises: what can chemistry do in the search for new strategies and approaches to solve this emergent problem? Although initially a variety of known chemical compounds – for other purposes – have been disappointingly tested against Ebola virus infection, more recently, specific molecules have been prepared. In this Perspective, we present a new approach directed to the design of efficient entry inhibitors to minimize the development of resistance by viral mutations. In particular,...

  17. Maleimide and Cyclooctyne-Based Hexakis-Adducts of Fullerene: Multivalent Scaffolds for Copper-Free Click Chemistry on Fullerenes

    Ramos Soriano, Javier; Reina, José J.; Illescas, Beatriz M.; Rojo, Javier; Martín, Nazario
    The synthesis of multivalent systems based on hexakisadducts of [60]fullerene employing a biocompatible copper-free click chemistry strategy has been accomplished. A symmetric hexakis-adduct of fullerene bearing 12 maleimide units (3) is reported, and it has been employed to carry out the thiol-maleimide Michael addition. To achieve orthogonal click addition, an asymmetric derivative bearing one maleimide and 10 cyclooctynes has been synthesized. The sequential and one-pot transformations of the two clickable groups have been explored, finding the best results in the case of the one-pot experiment. This route has been used to obtain a biocompatible hexakis-adduct appended with two different biomolecules,...

  18. Antiviral Activity of Self‐Assembled Glycodendro[60]fullerene Monoadducts

    Muñoz, Antonio; Illescas, Beatriz M.; Luczkowiak, Joanna; Lasala, Fátima; Ribeiro Viana, Renato; Rojo, Javier; Delgado, Rafael; Martín, Nazario
    A series of amphiphilic glycodendro[60]fullerene monoadducts were efficiently synthesized using the CuAAC “click chemistry” approach. These glycodendrofullerenes can self‐assemble in aqueous media, in a process favoured through π‐ π interactions between the [60]fullerene moieties. This aggregation process leads to big and well‐defined compact micelles with a uniform size and spherical‐shape. The supramolecular aggregate was characterized using electronic microscopy (SEM and TEM), light scattering methods (DLS) and X‐ray methodologies (SAXS and XRD). The antiviral efficiency of these aggregates has been tested in an experimental infection assay using Ebola virus glycoprotein (EboGP) pseudotyped viral particles on Jurkat cells overexpressing DC‐SIGN and it...

  19. A C60‐aryne building block: Synthesis of a hybrid all‐carbon nanostructure

    García, D.; Rodríguez Perez, Laura; Herranz, M.Angeles; Peña, D.; Guitián, E.; Bailey, S.; Al-Galiby, Q.; Noori, M.; Lambert, C.J.; Pérez, D.; Martín, Nazario
    The synthesis of a [60]fullerene‐benzyne building block and its further chemical cycloaddition reaction with graphene has resulted in a new all‐carbon hybrid material which has been characterized by TGA, FTIR and Raman spectroscopies, XPS as well as AFM and TEM. Based on computational studies, the formation of both [2+2] and [4+2] cycloadducts on the graphene surface is feasible.

  20. Non-covalent graphene nanobuds from mono- and tripodal binding motifs

    Garrido, Marina; Calbo, Joaquín; Rodríguez Perez, Laura; Aragó, Juan; Ortí, Enrique; Herranz, M.Angeles; Martín, Nazario
    Graphene nanobuds were prepared via the non-covalent anchoring of C60-based molecules endowed with one or three pyrene units. TGA, FTIR, UV-Vis and TEM investigations confirmed the nanohybrids formation. For the two molecular derivatives, striking differences were determined in their interaction with graphene or carbon surfaces by Raman, cyclic voltammetry and molecular mechanics calculations, revealing the important role of pyrene adsorption in the electronic properties of the nanohybrids.

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