Ruthenium molecular complexes immobilized on graphene as active catalysts for the synthesis of carboxylic acids from alcohol dehydrogenation

Ruthenium complexes containing N-heterocyclic carbene ligands functionalized with different polyaromatic groups (pentafluorophenyl, anthracene, and pyrene) are immobilized onto the surface of reduced graphene oxide. The hybrid materials composed of organometallic complexes and graphene are obtained in a single-step process. The hybrid materials are efficient catalysts for the synthesis of carboxylic acids from the dehydrogenation of alcohols in aqueous media. The catalytic materials can be recycled up to ten times without significant loss of activity. The catalytic activity of the pyrene derivative, Pyr-Ru (3) is enhanced when the ruthenium complex is anchored onto the surface of graphene. The carbonaceous material limits the degradation of the ruthenium complex resulting in increased activity and requiring lower catalyst loadings. The catalytic process of the pyrene hybrid material is heterogeneous in nature due to the strong interaction between the pyrene and graphene. The catalytic process of the anthracene and pentafluorophenyl hybrid materials is governed by the so-called ‘boomerang effect’. The ruthenium molecular complex is released from and returned to the graphene surface during the catalytic reaction. Mechanistic insight has been obtained experimentally and theoretically. The energy profile suggests that the rate-determining step is the water nucleophilic attack to a coordinated aldehyde complex to form a gem-diolate complex.The authors thank the financial support from MINECO (CTQ2015-69153-C2-2-R and CTQ2015- 67461-P), Generalitat Valenciana (AICO/2015/039), Universitat Jaume I (P1.1B2015-09) and Universidad de Zaragoza (UZ2014-CIE-01)

síntesis de complejos organometálicos orientados a la activación dell nitrógeno molecular

El trabajo de fin de grado que aquí se presenta tiene como objetivo científico fundamental la preparación de sistemas organometálicos de molibdeno estabilizados por ligandos bidentados de tipo carbeno N-heterocíclico. Este objetivo requiere de una serie de pasos que se han ido cumplimentando sucesivamente. En primer lugar se han preparado las sales orgánicas de tipo bis-imidazolio que sirven de precursores para los ligandos deseados. Así, se ha desarrollado la síntesis de bromuro y hexafluoruro de N-mesitil-N’-2-piridil-imidazolio y también de dibromuro de 1,1’-metilen-3,3’-bis-(mesitil)-imidazolio. Ambos sustratos han sido obtenidos a través de reacciones de tipo SN2 entre 2-bromo-piridina y dibromometano, respectivamente, con N-mesitil-imidazol. El tratamiento posterior de dichas especies con una base no nucleófila permite su deprotonación y generación de las correspondientes especies de tipo piridina-carbeno y bis-carbeno. A continuación se han estudiado vías de acceso a nuevas especies de molibdeno estabilizadas por los citados ligandos, por generación in-situ de los dos sustratos carbeno N-heterocíclico y tratamiento, en condiciones de activación térmica, con hexacarbonil-molibdeno. Así, la primera reacción ha dado lugar al derivado tetracarbonil-2-C,N-(N-mesitil-N’-2-piridil-imidazol-2-ilideno)molibdeno (0), resultado del desplazamiento en el centro metálico de dos ligandos carbonilo por el ligando bidentado. Sin embargo, la segunda reacción ha generado el derivado tetracarbonil-bis(1-N-(N-mesitil-imidazol))molibdeno (0), que se forma previa degradación del sustrato bis-carbeno al imidazol de partida. De acuerdo con ello, este último complejo se puede obtener alternativamente por reacción directa del hexacarbonil-molibdeno con N-mesitil-imidazol en condiciones de activación térmica

Iridium complexes catalysed the selective dehydrogenation of glucose to gluconic acid in water

[EN] We describe an unprecedented catalytic dehydrogenation of glucose by homogeneous catalysts. Iridium(iii) complexes containing the fragment [Cp*Ir(NHC)](2+) (NHC = N-heterocyclic carbene ligand) are shown to be very active and highly selective catalysts for the dehydrogenation of glucose to gluconic acid and molecular hydrogen. Glucose is converted to gluconic acid at a catalyst loading of 2 mol%, at reflux in water, without additives and with a selectivity of over 95%. Experimental evidence obtained by H-1 NMR spectroscopy and mass spectrometry (ESI/MS) reveals the formation of iridium coordinated to glucose and gluconic acid species. A plausible mechanism is proposed, based on the experimental evidence and supported by DFT calculations.The authors thank the MINECO (Severo Ochoa, CTQ2015-69153-C2-1-R, CTQ2015-69153-C2-2-R and CTQ2015-67461-P), Diputacion General de Aragon (Grupo Consolidado E21) and Universitat Jaume I (P1.1B2015-09) for financial support. P. Borja thanks the Universitat Jaume I for a postdoctoral grant. The authors are very grateful to the 'Serveis Centrals d'Instrumentacio Cientifica (SCIC)' of the Universitat Jaume I, S. Fuertes (Universidad of Zaragoza) for data collection of the X-ray structure of 4 and to the Instituto de Biocomputacion y Fisica de Sistemas Complejos (BIFI) and the Centro de Supercomputacion de Galicia (CESGA) for the generous allocation of computational resources.Borja, P.; Vicent, C.; Baya, M.; García Gómez, H.; Mata, JA. (2018). Iridium complexes catalysed the selective dehydrogenation of glucose to gluconic acid in water. Green Chemistry. 20(17):4094-4101. https://doi.org/10.1039/c8gc01933aS409441012017Corma, A., Iborra, S., & Velty, A. (2007). Chemical Routes for the Transformation of Biomass into Chemicals. Chemical Reviews, 107(6), 2411-2502. doi:10.1021/cr050989dBesson, M., Gallezot, P., & Pinel, C. (2013). Conversion of Biomass into Chemicals over Metal Catalysts. 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Catalytic Dehydrogenative Coupling of Hydrosilanes with Alcohols for the Production of Hydrogen On-demand: Application of a Silane/Alcohol Pair as a Liquid Organic Hydrogen Carrier

The compound [Ru(p-cym)(Cl)2(NHC)] is an effective catalyst for the room-temperature coupling of silanes and alcohols with the concomitant formation of molecular hydrogen. High catalyst activity is observed for a variety of substrates affording quantitative yields in minutes at room temperature and with a catalyst loading as low as 0.1 mol %. The coupling reaction is thermodynamically and, in the presence of a Ru complex, kinetically favourable and allows rapid molecular hydrogen generation on-demand at room temperature, under air, and without any additive. The pair silane/alcohol is a potential liquid organic hydrogen carrier (LOHC) for energy storage over long periods in a safe and secure way. Silanes and alcohols are non-toxic compounds and do not require special handling precautions such as high pressure or an inert atmosphere. These properties enhance the practical applications of the pair silane/alcohol as a good LOHC in the automotive industry. The variety and availability of silanes and alcohols permits a pair combination that fulfils the requirements for developing an efficient LOHC

Terminal Au-N and Au-O Units in Organometallic Frames

Since gold is located well beyond the oxo wall, chemical species with terminal Au−N and Au−O units are extremely rare and limited to low coordination numbers. We report here that these unusual units can be trapped within a suitable organometallic frame. Thus, the terminal auronitrene and auroxyl derivatives [(CF3)3AuN]− and [(CF3)3AuO]− were identified as local minima by calculation. These open-shell, high-energy ions were experimentally detected by tandem mass spectrometry (MS2): They respectively arise by N2 or NO2 dissociation from the corresponding precursor species [(CF3)3Au(N3)]− and [(CF3)3Au(ONO2)]− in the gas phase. Together with the known fluoride derivative [(CF3)3AuF]−, they form an interesting series of isoleptic and alloelectronic complexes of the highly acidic organogold(iii) moiety (CF3)3Au with singly charged anions X− of the most electronegative elements (X=F, O, N). Ligand-field inversion in all these [(CF3)3AuX]− species results in the localization of unpaired electrons at the N and O atoms

Cross-sectional and prospective relationship between physical activity and depression symptoms

© The Author(s) 2020. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.This study aimed to analyse the cross-sectional and prospective relationship between moderate and vigorous physical activity (PA) and depression symptoms. This study analysed 32,392 European late middle-aged to older adults, from 14 European countries across a 4-year follow-up. Data was collected in the fourth (in 2011) and sixth (in 2015) wave, from the Survey of Health, Ageing and Retirement in Europe (SHARE). For the present analysis, participants were considered who responded to the EURO-D 12-item scale of depression symptoms and reported the intensity and frequency of PA. ANCOVAs were conducted to assess the cross-sectional and prospective associations. For both men and women, engaging in moderate or vigorous PA in 2011 was associated with a lower score of depression in 2011 and 2015. From the prospective analysis, moderate and vigorous PA in 2011 was inversely associated with the score of depression. This association remains significant in the fully adjusted for self-rated health, sociodemographic characteristics, and the presence of chronic diseases. Moderate and vigorous PA at least once a week is negatively related to the score of depression, both in men and women. PA is negatively associated with depression symptoms, and from prospective analysis PA predicts lower depression scores 4 years later.info:eu-repo/semantics/publishedVersio

Trifluorometil Derivados de Ag(III)

e ha llevado a cabo un amplio estudio de la química de los trifluorometil complejos de plata(III). A tal fin se ha sintetizado el complejo homoléptico de AgI: [PPh4][AgI(CF3)2], para utilizarlo como producto de partida. Por reacción de este con diferentes oxidantes se han preparado tanto el derivado homoléptico [PPh4][AgIII(CF3)4], como los derivados heterolépticos [PPh4][(CF3)3AgIIICl] y [PPh4][trans-(CF3)2AgIIIX2] (X = Cl, Br). A su vez, el complejo [PPh4][(CF3)3AgIIICl] reacciona con AgF para formar [PPh4][(CF3)3AgIIIF], que constituye el primer ejemplo de un fluoruro organometálico de AgIII. Asimismo, sirve como puerta de entrada a los derivados [PPh4][(CF3)3AgIIIX] (X = Br, I, CN, N3) al reaccionar rápidamente con Me3SiX. Además, el compuesto [PPh4][(CF3)3AgIIIF] reacciona con diferentes tioles HSR, dando lugar a los derivados [PPh4][(CF3)3AgIII(SR)], que se descomponen fácilmente liberando los correspondientes trifluorometiltioéteres CF3SR. La descomposición mayoritaria en fase gas de los complejos [(CF3)3AgIIIX]– consiste en la pérdida consecutiva de dos radicales CF3•, formando los aniones mixtos lineales [(CF3)AgIX]–. A su vez, éstos sufren un proceso de extrusión de CF2, dando lugar a la formación de las especies triatómicas de fórmula [FAgIX]. Se ha observado también que los complejos [PPh4][trans-(CF3)2AgIIIX2] (X = Cl, Br) muestran una cierta tendencia a asociar un ligando adicional X–, poniendo de manifiesto un claro carácter electrófilo del metal. Este proceso asociativo está gobernado por un delicado equilibrio termodinámico. En el caso de X = Br dicho equilibrio está comparativamente más desplazado hacia la formación de un producto pentacoordinado. La determinación estructural por difracción de rayos X del complejo [PPh4]2[(CF3)2AgIIIBr3] ha puesto de manifiesto que posee una estructura de pirámide trigonal, sin precedentes en la química de AgIII. Las estructuras electrónicas de todos los compuestos estudiados por métodos teóricos presentan Inversión de Campo Ligando (ICL). Es el caso también de la serie completa de derivados homolépticos: [MIII(CF3)4]– (M = Cu, Ag, Au). Al excitar con luz UV estos complejos se produce la ruptura heterolítica de los enlaces M–C y se generan radicales CF3•. Ello constituye una prueba de la covalencia del enlace M–CF3. Cabe destacar finalmente que el complejo [PPh4]2[(CF3)2AgIIIBr3] es el primer derivado pentacoordinado para el que se ha descrito una estructura electrónica con ICL. <br /

Longitudinal association between sport participation and depressive symptoms after a two-year follow-up in mid-adolescence

Sport participation has been advocated as a strategy to improve adolescents’ mental health. However, how these variables evolve during the adolescent years is uncertain. The objective of the present work was to examine the longitudinal associations of sports participation and depressive symptoms in adolescents. Participants were 525 Spanish adolescents (50.3% boys), aged between 12 and 15 years old (M = 13.45, SD = 0.69). They were enrolled in 18 secondary schools located in Andalusia (Spain) in the first two academic years of Compulsory Secondary Education. Data were collected in three waves, separated by one year, by administering self-report measures of depressive symptoms and sport participation. Repeated measures analyses of variance were conducted to examine the change in depressive symptoms and sport participation, and a latent growth curve model was tested to examine the change in depressive symptoms controlling initial sport participation and gender. At each wave, more frequent sport participation was related to lower depressive symptoms. Two years after the first assessment, adolescents became more depressed but not more active. Less active adolescents had more depressive symptoms in each assessment time. At all moments of assessment, girls were less active and reported more depressive symptoms. Moreover, girls had a higher increase in depressive symptoms than boys. Promotion of physical activity (PA) as a mental health strategy needs to consider gender differences as boys and girls have different patterns of presentation of depressive symptoms throughout adolescence

Síntesis y Reactividad de Complejos Benzamidato de Platino (II). Estudio de sus propiedades

Se han obtenido nuevos complejos de platino con ligandos amidato a partir de especies de tipo bisnitrilo. Los complejos bisamidato son capaces de establecer fuertes enlaces de hidrógeno claves en su estabilización, lo que ha quedado demostrado por su estudio experimental y teórico. A partir de los complejos amidato se han sintetizado diversas especies por reacciones de sustitución y oxidación. Adicionalmente, se ha completado un complejo proceso de inserción de SO2 con la monohidratación de éste mediante un mecanismo por etapas favorable energéticamente. Fruto de uno de los resultados de los procesos de sustitución se ha obtenido un nuevo complejo pincer PNC por acoplamiento in situ entre un ligando difenilfosfanobenzaldehído y un ligando amidato, ambos coordinados al centro metálico. A partir de este nuevo complejo pincer se han sintetizado una amplia familia de este tipo de complejos de diferentes características. Los complejos obtenidos se han estudiado como potenciales agentes antitumorales frente a células HeLa y Jurkat. Ha quedado demostrado que los complejos pincer son más activos que los complejos amidato frente a las células cancerígenas. En especial, merecen ser destacados los complejos pincer catiónicos 15b y 19a que son capaces de discriminar entre células normales y tumorales, por lo que son buenos candidatos para avanzar a nuevas fases de ensayos antitumorales.<br /

Sigma-bond activation reactions induced by unsaturated Os(IV)-hydride complexes

Unsaturated osmium(IV)-hydride complexes are diamagnetic six-coordinate d4 species, which undergo distortion from the octahedral geometry to form unusual D4d or C2v geometries. They display a notable ability to activate H–H, B–H, C–H, C–C, C–O, C–Br, Si–H, Sn–H, N–H, or O–H bonds of a wide range of inorganic, organic, and organometallic molecules, including: molecular hydrogen, boranes, phosphines, heterocycles, olefins, dienes, enynes, allenes, allenedienes, alkynamides, alkylhalides, silanes, stannanes, diamines, oximes, metal-nucleosides, or molecular oxygen. The activations yield, among other organometallic derivatives, dihydrogen, borane, borinium, alkylidene, alkylidyne, vinylidene, NHC, silylene, stannyl, osmafuran, osmaisobenzofuran, osmabenzimidazolium, or azavinylidene complexes. A characteristic of these activation processes is that they do not result in an increase of the formal oxidation state of the metal center. Given the wide range of s-bond activations promoted by these compounds and the wide variety of complexes formed, future interesting applications for them can be anticipated