Tuning PCP-Ir complexes: the impact of an N-heterocyclic olefin

A new PCP-type ligand based on an N-heterocyclic olefin (NHO) scaffold has been prepared. The flexibility of this ligand, which is able to adopt facial coordination modes in Ir(I) or meridional in Ir(III) complexes, can be attributed to the dual nature (ylide–olefin) of the NHO scaffold. This results in a rare case of olefin “slippage” that is supported by X-ray crystallography and DFT calculations.This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO/FEDER) (CONSOLIDER INGENIO CSD2009-0050, CTQ2011-27593 and CTQ2012-35665 projects) and the DGA/FSE-E07. The support from KFUPM-University of Zaragoza research agreement and the Centre of Research Excellence in Petroleum Refining & KFUPM is gratefully acknowledged.Peer Reviewe

Novel homogeneous Ir-catalysts: Ligand design, applications and mechanisms

Resumen del trabajo presentado a la 2nd World Chemistry Conference and Exhibition (WCCE), celebrada en Valencia (España) del 9 al 11 de julio de 2018.This presentation will deal with two main subjects: (i) the preparation ofthe frrst PCP-type ligand based on an N-heterocyclic olefm (NHO) scaffold, accompanied by an evaluation of the impact of this type of ligand in the activity of iridium complexes in several relevant catalytic processes; and (ii) the development of well- defined Ir-NHC complexes as catalysts for the dehydrogenative silylation of aromatic C-H bonds. (i) A great variety of pincer complexes has been reported in the literature. In particular, transition metal complexes containing PCP pincer ligands have shown remarkable activities in relevant catalytic processes. Recent work by us on this subject has resulted in the preparation of an ewPCP-type ligand based on an N- heterocyclic olefin (NHO) scaffold. The flexibille coordination of this NHO-based PCP-ligand can be attributed to the dual nature (ylide-olefm) oftbe NHO. Iridium(I) complexes featuring this ligand show excellent activities in transfer hydrogenation reactions. The active species ([Ir(KP,C,P'-NHO-PPh2)(iPrO)]), formed via COD dissociation and subsequent isopropoxide coordination, features an NHO moiety that behaves as a hemilabile ligand, which allows the catalyst to adopt stabJe square planar geometries in the transition states, thus reducing the energetic barrier of the process. More recently, we have tested the activity ofthese complexes in the dehydrogenation of formic acid, showing outstanding activities in water and in neat formicacid. (ii) The preparation of fine chernicals by the catalytic functionalization of C-H bonds has seen an outstanding development in recent years, with borylation and silylation reactions being prominent examples of this chemistry. In this regard, the versatility of oganosilicon compounds can be attributed to the low cost and non-toxic nature of silicon reagents, together with their straight forward functionalization by various reactions. Moreover, conjugated organosilicon materials are attractive targets per se owing to their unique properties, which permit a widespread applicability in the field of organic electronics and photonics. Most of the catalysts employed so far for this reaction are generated >in situ> from commercial metal precursors and ligands. Hence, we have focused on the development of well-defined organometallic catalysts bearing appropriate ligands in order to improve the efficiency of current silylation catalysts. In particular, the use of NHC-Ir (III) complex [Ir(H)2(IPr)(py)3][BF4] (IPr = 1 ,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene) as a catalyst has allowed for the preparation of a wide range of aryl- and heteroarylsilanes. The directed and non-directed functionalization of C-H bonds has been accomplisbed successfully using the areneas tbe limiting reagent and a variety of hydrosilanes, including Et3SiH, Ph2MeSiH, PhMe2SiH, Ph3SiH and(Et0)3SiH.Peer Reviewe

Source apportionment of the carcinogenic potential of polycyclic aromatic hydrocarbons (PAH) associated to airborne PM10 by a PMF model

In order to perform a study of the carcinogenic potential of polycyclic aromatic hydrocarbons (PAH), benzo(a)pyrene equivalent (BaP-eq) concentration was calculated and modelled by a receptor model based on positive matrix factorization (PMF). Nineteen PAH associated to airborne PM10 of Zaragoza, Spain, were quantified during the sampling period 2001-2009 and used as potential variables by the PMF model. Afterwards, multiple linear regression analysis was used to quantify the potential sources of BaP-eq. Five sources were obtained as the optimal solution and vehicular emission was identified as the main carcinogenic source (35 %) followed by heavy-duty vehicles (28 %), light-oil combustion (18 %), natural gas (10 %) and coal combustion (9 %). Two of the most prevailing directions contributing to this carcinogenic character were the NE and N directions associated with a highway, industrial parks and a paper factory. The lifetime lung cancer risk exceeded the unit risk of 8.7 × 10-5 per ng/m3 BaP in both winter and autumn seasons and the most contributing source was the vehicular emission factor becoming an important issue in control strategies.Authors would like to thank Aula Dei-CSIC (Dr R. Gracia) for the meteorological data and the Ministry of Science and Innovation (MICIIN) for supporting the project CGL2009-14113-C02-01 and the Plan E for the co-funding. They would also like to thank the MICIIN for the contract of A.I. and the MICYT for the Ramon y Cajal contract of J.M.L.Peer Reviewe

Nature and sources of particle associated polycyclic aromatic hydrocarbons (PAH) in the atmospheric environment of an urban area.

The total PAH associated to the airborne particulate matter (PM10) was apportioned by one receptor model based on positive matrix factorization (PMF) in an urban environment (Zaragoza city, Spain) during February 2010-January 2011. Four sources associated with coal combustion, gasoline, vehicular and stationary emissions were identified, allowing a good modelling of the total PAH (R(2) = 0.99). A seasonal behaviour of the four factors was obtained with higher concentrations in the cold season. The NE direction was one of the predominant directions showing the negative impact of industrial parks, a paper factory and a highway located in that direction. Samples were classified according to hierarchical cluster analysis obtaining that, episodes with the most negative impact on human health (the highest lifetime cancer risk concentrations), were produced by a higher contribution of stationary and vehicular emissions in winter season favoured by high relative humidity, low temperature and low wind speed.Authors would like to thank Aula Dei-CSIC (R. Gracia) for providing the meteorological data as well as the Ministry of Science and Innovation (Spain) (MICIIN) and the E plan for the co-funding through the project CGL2009-14113-C02-01. JM López (Ramón y Cajal contract) and A. Iturmendi (contract) would also like to thank the MICYT and the MICIIN.Peer Reviewe

Source apportionment of atmospheric PM2.5-bound polycyclic aromatic hydrocarbons by a PMF receptor model. Assessment of potential risk for human health

5 figures, 2 table, 11 págs.One year sampling (2011-2012) campaign of airborne PM2.5-bound PAH was performed in Zaragoza, Spain. A source apportionment of total PAH by Positive Matrix Factorization (PMF) was applied in order to quantify potential PAH pollution sources. Four sources were apportioned: coal combustion, vehicular emissions, stationary emissions and unburned/evaporative emissions. Although Directive 2004/107/EC was fulfilled regarding benzo(a)pyrene (BaP), episodes exceeding the limit value of PM2.5 according to Directive 2008/50/EC were found. These episodes of high negative potential for human health were studied, obtaining a different pattern for the exceedances of PM2.5 and the lower assessment threshold of BaP (LATBaP). In both cases, stationary emissions contributed majority to total PAH. Lifetime cancer risk exceeded the unit risk recommended by the World Health Organization for those episodes exceeding the LATBaP and the PM2.5 exceedances for the warm season. For the cold season, the risk was higher for the LATBaP than for the PM2.5 exceedances.The authors would like to thank the Industry and Innovation department of Gobierno de Aragón (DGA), the Fondo Social Europeo “Construyendo Europa desde Aragón” and the Ministry of Science and Innovation (Spain) through the project CGL2009-14113-C02-01 for partial financial support. J.M. López would also like to thank the MICIIN for his Ramón and Cajal contract.Peer reviewe

Source apportionment of airborne PAH in an urban environment

Resumen del trabajo presentado al Sino-European Symposium on Environmental and Health (SESEH), celebrado en Galway (Irlanda) del 20 al 25 de agosto de 2012.Urban environments constitute one of the main focuses of anthropogenic polycyclic aromatic hydrocarbons (PAH) generation. A study regarding PAH bounded to the airborne particulate matter PM10 was carried out in Zaragoza city, Spain during 2010-2011. The concentrations of 19 PAH were analyzed by gas chromatography with mass spectrometry mass spectrometry detection. The sources of PAH to ambient air in Zaragoza were determinad by using the UNMIX model in order to discern qualitatively and quantitatively the main pollution sources affecting the sampling site. When the total PAH concentrations obtained experimentally were compared to the total PAH concentrations modeled by the UNMIX, the correlation was excellent. A total of tour sources were identified by the model related to different anthropogenic pollution sources where the heavy-duty diesel vehicles and the traffic emissions factors were identified as the major contributing sources of PAH. Episodes were classified as a function of BaP concentrations, one of the most carcinogenic PAH according to Directiva 2004/107/EC and the contribution of pollution sources was compared to the average PAH episodes. The highest BaP concentrations, involving a higher risk for human health, were produced during the cold season showing a remarkable increase in the heavy-duty diesel vehicles factor contribution.Peer reviewe

Estudio de las fuentes antropogénicas de los hidrocarburos aromáticos policíclicos (PAH) asociados a la materia particulada atmosférica PM10 en Zaragoza

Resumen del póster presentado a las 5ª Jornada de Jóvenes Investigadores de Química y Física en Aragón, celebradas en Zaragoza el 4 de diciembre de 2012.[Introducción y objetivos]: Los hidrocarburos aromáticos policíclicos (PAH) son una familia de compuestos que se caracterizan por tener dos o más anillos de benceno fusionados. Su principal fuente de emisión a la atmósfera la constituyen los procesos de combustión incompleta de compuestos orgánicos, por lo que tiene un importante componente antropogénico (tráfico, calefacción doméstica, generación de energía ... ) aunque también se originan en procesos naturales como volcanes, incendios forestales, etc. Debido a las propiedades carcinogénicas y mutagénicas de los PAH, es importante conocer cuáles son sus principales fuentes antropogénicas, para poder cumplir la legislación vigente y adoptar las medidas de reducción necesarias, mejorando así la calidad del aire. El objetivo de este proyecto es identificar y cuantificar cuáles son las principales fuentes antropogénicas de los PAH asociados a la materia particulada de tamaño <= 10 μm (PM10) en la ciudad de Zaragoza utilizando para ello un modelo de receptor basado en técnicas estadísticas, concretamente, el modelo de factorización matricial, PMF.[Metodología]: El estudio se ha realizado en el campus Rio Ebro de Zaragoza. Para el muestreo (Febrero 2010- Enero 2011) de los PAH asociados a la materia particulada (PM) atmosférica se ha utilizado un captador de alto volumen con cabezal que permite capturar la PM menor o igual que 10 μm (PM1O) a través de un filtro de fibra de cuarzo. Los PAH contenidos en la PM10 se extraen mediante Soxhlet para, tras una etapa de concentración y limpieza llevar a cabo su análisis a través de cromatografia de gases con detección masas-masas mediante el método del estándar interno.[Discusión de los resultados y conclusiones]: La concentración media obtenida del total de PAH durante el periodo de muestreo completo es 1.78±1.86 ng/m3, encontrándose un comportamiento estacional estadísticamente significativo al 99% entre la época cálida (verano, primavera) y la época fría (invierno, otoño) con concentraciones cuatro veces mayor durante la época fría. Uno de los PAH de los que más interesa conocer su concentración es el benzo(a)pireno (BaP), ya que, según la IARC está clasificado como cancerígeno para humanos. La concentración media obtenida para el BaP es 0.09±0.11 ng/m3, valor que no supera el 1.0 ng/m3 , establecido por la Directiva 2004/107/EC, aunque sí se producen superaciones para determinadas fechas correspondientes al periodo de invierno. La aplicación del modelo PMF al total de P AH permite obtener una buena correlación entre el total de PAH obtenido experimentalmente y el obtenido a través del modelo (R2=0.99) proporcionando un total de cuatro factores que se han atribuido a las siguientes fuentes: "Combustión de carbón" (contribuye al 24% del total de PAH), "emisiones vehiculares" (32%), "emisiones de gasolina" (20%) y "emisiones industriales" (24%). En conclusión, el modelo de receptor PMF ha permitido, satisfactoriamente, la identificación y cuantificación de cuatro fuentes asociadas al total de PAH contenido en la PM10 de Zaragoza. Además se ha comprobado que las emisiones vehiculares son las que más contribuyen al total de PAH y que la época del año en la que mayor riesgo carcinogénico existe es en la época fría, donde las condiciones meteorológicas junto con la contribución de fuentes asociadas con la calefacción doméstica, favorecen la concentración de PAH en la fase particulada.Peer reviewe

Receptor modeling for source apportionment of particle bounded polycyclic aromatic hydrocarbons at an urban location in Spain

Trabajo presentado a la 15th Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes, celebrada en Madrtid (España) del 6 al 9 de mayo de 2013.Polycyclic Aromatic Hydrocarbons (PAH) are a group of organic pollutants, which are mainly formed from both natural and anthropogenic sources. PAH are an environmental concern because their carcinogenic, mutagenic and immuno-toxic properties and for this reason, EPA (Environmental Protection Agency of United States) has included 16 PAH on its list of priority pollutants. In this paper, the PAH associated to the airborne particulate matter less or equal than 2.5 μm (PM2.5) were studied by using two receptor models based on multivariate statistical tools (UNMIX and PMF) in the city of Zaragoza, Spain. A high volume air sampler with a PM2.5 cut off was used to collect samples from June 2011-May 2012. PAH on the particle phase were extracted by Soxhlet and 19 PAH were analyzed by gas-chromatography with mass spectrometry mass spectrometry detection (GC-MS-MS). Chrysene, benzo(b)fluoranthene, fluoranthene, pyrene and benzo(e)pyrene represented the 47% of the average total PAH. Good correlations were obtained between the experimental and the modeled PAH by both models and a comparison of the different quantified factors was carried out. Despite no episodes of benzo(a)pyrene (BaP) equal or higher than 1.0 ng/m3 were obtained (Directive 2004/107/EC), the concentration of PM2.5 exceeded the limit value of 25 μg/m3 (Directive 2008/50/EC) in several occasions. These episodes were interpreted according to both models in order to check the impact of different anthropogenic sources, especially the traffic emissions factor.Authors would like to thank the Industry and Innovation department of Gobierno de Aragón (DGA), the Fondo Social Europeo “Construyendo Europa desde Aragón” and the Ministry of Science and Innovation (Spain) through the project CGL2009-14113-C02-01for partial financial support. J.M. López would also like to thank the MICIIN for his Ramón and Cajal contract.Peer reviewe