gem-selective cross-dimerization and cross-trimerization of alkynes with silylacetylenes promoted by a Rhodium-Pyridine-N-heterocyclic carbene catalyst

The gem-selective cross-dimerization and -trimerization of silylacetylenes with alkynes through C[BOND]H activation using a rhodium(I)–pyridine–N-heterocyclic carbene catalyst have been developed. This reaction is applied to various aliphatic or aromatic terminal alkynes, internal alkynes, and gem-1,3-disubsituted enynes to afford the corresponding enynes and dienynes with high regio- and stereoselectivities and in good isolated yields (up to 91 %).Financial support from the Spanish Ministerio de Economía y Competitividad (MEC/FEDER) of Spain Project (CTQ2010-15221), the Diputación General de Aragón (E07), the KFUPMUNIZAR agreement, and CONSOLIDER INGENIO-2010, under the Project MULTICAT (CSD2009-00050) are gratefully acknowledged. L. R.-P. thanks CONACyT (Mexico, 186898 and 204033) for a postdoctoral fellowship.Peer Reviewe

Super nucleation and orientation of poly (butylene terephthalate) crystals in nanocomposites containing highly reduced graphene oxide

The ring opening polymerization of cyclic butylene terephthalate into poly (butylene terephthalate) (pCBT) in the presence of reduced graphene oxide (RGO) is an effective method for the preparation of polymer nanocomposites. The inclusion of RGO nanoflakes dramatically affects the crystallization of pCBT, shifting crystallization peak temperature to higher temperatures and, overall, increasing the crystallization rate. This was due to a super nucleating effect caused by RGO, which is maximized by highly reduced graphene oxide. Furthermore, combined analyses by differential scanning calorimetry (DSC) experiments and wide angle X-ray diffraction (WAXS) showed the formation of a thick {\alpha}-crystalline form pCBT lamellae with a melting point of ~250 {\deg}C, close to the equilibrium melting temperature of pCBT. WAXS also demonstrated the pair orientation of pCBT crystals with RGO nanoflakes, indicating a strong interfacial interaction between the aromatic rings of pCBT and RGO planes, especially with highly reduced graphene oxide. Such surface self-organization of the polymer onto the RGO nanoflakes may be exploited for the enhancement of interfacial properties in their polymer nanocomposites

Hybrid simulation-optimization based approach for the optimal design of single-product biotechnological processes

In this work, we present a systematic method for the optimal development of bioprocesses that relies on the combined use of simulation packages and optimization tools. One of the main advantages of our method is that it allows for the simultaneous optimization of all the individual components of a bioprocess, including the main upstream and downstream units. The design task is mathematically formulated as a mixed-integer dynamic optimization (MIDO) problem, which is solved by a decomposition method that iterates between primal and master sub-problems. The primal dynamic optimization problem optimizes the operating conditions, bioreactor kinetics and equipment sizes, whereas the master levels entails the solution of a tailored mixed-integer linear programming (MILP) model that decides on the values of the integer variables (i.e., number of equipments in parallel and topological decisions). The dynamic optimization primal sub-problems are solved via a sequential approach that integrates the process simulator SuperPro Designer® with an external NLP solver implemented in Matlab®. The capabilities of the proposed methodology are illustrated through its application to a typical fermentation process and to the production of the amino acid L-lysine.Support from the Spanish Ministry of Education and Science (projects DPI2008-04099 and CTQ2009-14420-C02) and the Spanish Ministry of External Affairs (projects A/023551/09, A/031707/10 and HS2007-0006)

Rhodium(I)-N-heterocyclic carbene catalyst for selective coupling of N-vinylpyrazoles with alkynes via C-H activation

The complex [Rh(μ-Cl)(IPr)(η2-coe)]2 {IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-carbene, coe = cis-cyclooctene} efficiently catalyzes the coupling of alkynes and N-vinylpyrazole via C–H activation, leading to Markovnikov-selective butadienylpyrazole derivatives under mild conditions. A straightforward approach to cross-conjugated acyclic trienes is also operative through a one-pot alkyne dimerization-hydrovinylation tandem reaction. The proposed mechanism involves C–H activation of vinylpyrazole directed by nitrogen coordination to the metallic center. Subsequent alkyne coordination, insertion, and reductive elimination steps lead to the coupling products. Several key intermediates participating in the catalytic cycle have been detected and characterized, including a κ-N, η2-C═C coordinated vinylpyrazole complex and a RhIII-hydride-alkenyl species resulting from the C–H activation of the vinylpyrazole.Financial support from the Spanish Ministerio de Economía y Competitividad (MEC/FEDER) of Spain Projects (CTQ2010-15221), the Diputación General de Aragón (E07), the ARAID Foundation, and CONSOLIDER INGENIO-2010, under the Project MULTICAT (CSD2009-00050) are gratefully acknowledged. L. R.-P. thanks CONACyT (Mexico, 186898 and 204033) for a postdoctoral fellowship.Peer Reviewe

Identifying spatial and seasonal patterns of river water quality in a semiarid irrigated agricultural Mediterranean basin

A detailed understanding of the study area is essential to achieve key information and optimize the monitoring, analysis, and evaluation of water quality of natural ecosystems that have been highly transformed into agricultural areas. Using classification techniques like the hierarchical cluster analysis (CA) and partial triadic analysis (PTA), we assessed the sources of water pollution and the seasonal influence of human activities in water composition in a river basin from northeastern Spain. The results suggested that a strong connection existed between water quality and the seasonality of the human activities. The CA showed the spatial relationship between water chemistry and the adjacent land uses. The PTA associated the analyzed variables to their pollutant source. Electrical conductivity (EC), Cl−, SO4 2−–S, Na+, and Mg2+ ions were related with agricultural sources, whereas NH4 +–N, PT, and PO4 3−–P were linked with urban polluted sites. Concentration of NO3ˉ–N was associated with urban land use. Differences in water composition according to the irrigation intensity were also found during the irrigation season. The statistical tools used in this work, especially the PTA, allowed us to jointly analyze the spatial and seasonal components of water pollutant trends. We obtained a more comprehensive knowledge of water quality patterns in the study area, which will be essential when taking measures to minimize the effects of water pollution.This work is part of the AGUAFLASH project funded by the Program of Territorial Cooperation “Interreg IVB-SUDOE” (SOE1/P2/F146) which is funded by EU FEDER. Thanks are given to Comarca de Los Monegros for its consistent cooperation in the development of this project. We thank C. Pedrocchi, J. Cervantes, S. G. Eisman, M. García, S. Pérez and A. Barcos for their comments and their crucial assistance in the field and laboratory work. A. Calvo at CHE contributed with key formal cooperation to this work. We also wish to thank the AEMET (Spanish Meteorological Agency) for access to meteorological data. This work was also developed as Research Group E61 Aragon Goverment.Peer reviewe

The OTELO survey. A case study of [O III]4959,5007 emitters at <z> = 0.83

The OTELO survey is a very deep, blind exploration of a selected region of the Extended Groth Strip and is designed for finding emission-line sources (ELSs). The survey design, observations, data reduction, astrometry, and photometry, as well as the correlation with ancillary data used to obtain a final catalogue, including photo-z estimates and a preliminary selection of ELS, were described in a previous contribution. Here, we aim to determine the main properties and luminosity function (LF) of the [O III] ELS sample of OTELO as a scientific demonstration of its capabilities, advantages, and complementarity with respect to other surveys. The selection and analysis procedures of ELS candidates obtained using tunable filter (TF) pseudo-spectra are described. We performed simulations in the parameter space of the survey to obtain emission-line detection probabilities. Relevant characteristics of [O III] emitters and the LF([O III]), including the main selection biases and uncertainties, are presented. A total of 184 sources were confirmed as [O III] emitters at a mean redshift z=0.83. The minimum detectable line flux and equivalent width (EW) in this ELS sample are $\sim$5 $\times$ 10$^{-19}$ erg s$^{-1}$ cm$^{2}$ and $\sim$6 \AA, respectively. We are able to constrain the faint-end slope ($\alpha = -1.03\pm0.08$) of the observed LF([O III]) at z=0.83. This LF reaches values that are approximately ten times lower than those from other surveys. The vast majority (84\%) of the morphologically classified [O III] ELSs are disc-like sources, and 87\% of this sample is comprised of galaxies with stellar masses of M$_\star$ $<$ 10$^{10}$ M$_{\odot}$.Comment: v1: 16 pages, 6 figures. Accepted in Astronomy \& Astrophysics. v2: Author added in metadat

Double hydrophosphination of alkynes promoted by rhodium: The key role of an N-heterocyclic carbene ligand

The regioselective double hydrophosphination of alkynes mediated by rhodium catalysts is presented. The distinctive stereoelectronic properties of the NHC ligand prevent the catalyst deactivation by diphosphine coordination thereby allowing for the closing of a productive catalytic cycle

Ligand-controlled regioselectivity in the hydrothiolation of alkynes by rhodium N-heterocyclic carbene catalysts

Rh-N-heterocyclic carbene compounds [Rh(μ-Cl)(IPr)(ν 2- olefin)] 2 and RhCl(IPr)(py)(ν 2-olefin) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-carbene, py = pyridine, olefin = cyclooctene or ethylene) are highly active catalysts for alkyne hydrothiolation under mild conditions. A regioselectivity switch from linear to 1-substituted vinyl sulfides was observed when mononuclear RhCl(IPr)(py)(ν 2- olefin) catalysts were used instead of dinuclear precursors. A complex interplay between electronic and steric effects exerted by IPr, pyridine, and hydride ligands accounts for the observed regioselectivity. Both IPr and pyridine ligands stabilize formation of square-pyramidal thiolate-hydride active species in which the encumbered and powerful electron-donor IPr ligand directs coordination of pyridine trans to it, consequently blocking access of the incoming alkyne in this position. Simultaneously, the higher trans director hydride ligand paves the way to a cis thiolate-alkyne disposition, favoring formation of 2,2-disubstituted metal-alkenyl species and subsequently the Markovnikov vinyl sulfides via alkenyl-hydride reductive elimination. DFT calculations support a plausible reaction pathway where migratory insertion of the alkyne into the rhodium-thiolate bond is the rate-determining step. © 2012 American Chemical Society.Financial support from the Ministerio de Ciencia e Innovación (MICINN/FEDER) of Spain (Project CTQ2010-15221), the Diputación General de Aragón (E07), the ARAID Foundation under the program “Jóvenes Investigadores”, and CONSOLIDER INGENIO-2010, Projects MULTICAT (CSD2009-00050) and Factoría de Cristalización (CSD2006-0015) are gratefully acknowledged. R.C. thanks the CSIC and the European Social Fund for his Research Contract in the framework of the “Ramón y Cajal” Program.Peer Reviewe

San Pedro Mártir observations of microvariability in obscured quasars

Fast brightness variations are a unique tool to probe the innermost regions of active galactic nuclei (AGN). These variations are called microvariability or intra-night variability, and this phenomenon has been monitored in samples of blazars and unobscured AGNs. Detecting optical microvariations in targets hidden by the obscuring torus is a challenging task because the region responsible for the variations is hidden from our sight. However, there have been reports of fast variations in obscured Seyfert galaxies in X-rays, which rises the question whether microvariations can also be detected in obscured AGNs in the optical regime. Because the expected variations are very small and can easily be lost within the noise, the analysis requires a statistical approach. We report the use of a one-way analysis of variance, ANOVA, with which we searched for microvariability. ANOVA was successfully employed in previous studies of unobscured AGNs. As a result, we found microvariable events during three observing blocks: in two we observed the same object (Mrk 477), and in another, J0759+5050. The results on Mrk 477 confirm previous findings. However, since Mrk 477 is quite a peculiar target with hidden broad-line regions, we cannot rule out the possibility that we have serendipitously chosen a target prone to variations.This research has been supported by the Spanish Ministerio de Economía y Competitividad (MINECO) under the grant AYA2014-58861-C3-1. I.O. acknowledges support from the European Research Council (ERC) in the form of Advanced Grant, COSMICISM. J.A.D. is grateful for the support from the grant UNAM-DGAPA-PAPIIT IN110013 Program and the Canary islands CIE: Tricontinental Atlantic Campus. A.E. acknowledges support by the grant AYA2012-30789. J. I. González-Serrano is grateful for the support from AYA2011-29517-C03-02.Peer Reviewe

Bis(hydrosulfido)-bridged dinuclear rhodium(I) complexes as a platform for the synthesis of trinuclear sulfido aggregates with the core [MRh2(μ3-S2)] (M = Rh, Ir, Pd, Pt, Ru)

The reaction of [Rh(μ-SH)(CO)(PPh3)]2 or [Rh(μ-SH){P(OPh)3}2]2 with [Cp*MCl2]2 (M = Rh, Ir) in the presence of NEt3 afforded the Rh3 and IrRh2 sulfido-bridged compounds [Cp*M(μ3-S)2Rh2(CO)2(PPh3)2] (M = Rh, 1; Ir, 2) and [Cp*Rh(μ3-S)2Rh2{P(OPh)3}4] (3). The reaction with [MCl2(cod)] (M = Pd, Pt), cis-[PtCl2(PPh3)2] or [(η6-C6H6)RuCl2]2 under the same experimental conditions gave [(cod)M(μ3-S)2Rh2{P(OPh)3}4] (M = Pd, 6; Pt, 7), [(cod)M(μ3-S)2Rh2(CO)2(PPh3)2] (M = Pd, 8; Pt, 9), [(PPh3)2Pt(μ3-S)2Rh2(CO)2(PPh3)2] (10) and [(η6-C6H6)Ru(μ3-S)2Rh2(CO)2(PPh3)2] (12), with PdRh2, PtRh2 and RuRh2 trimetallic cores. The aggregates derived from [Rh(μ-SH)(CO)(PPh3)]2 were isolated as a mixture of trans and cis isomers in which the trans isomer predominates. The reaction of [Rh(μ-SH){P(OPh)3}2]2 with 2 equiv. of n-BuLi at 253 K followed by addition of [Cp*IrCl2]2 gave [Cp*Ir(μ3-S)2Rh2{P(OPh)3}4] (4) and [Cp*2ClIr2(μ3-S)2Rh{P(OPh)3}2] (5) in a 3:2 ratio. The RuRh2 compound [(η6-C6H6)Ru(μ3-S)2Rh2{P(OPh)3}4] (11) was prepared similarly from [Rh(μ-SH){P(OPh)3}2]2 and [(η6-C6H6)RuCl2]2 using n-BuLi as a deprotonating agent. The molecular structures of compounds 3, 6, 7, 9 and 11 have been determined by X-ray analysis. The trinuclear complexes exhibit an asymmetric triangular metal core with two triply bridging sulfido ligands resulting in a distorted trigonal-bipyramidal M3(μ3-S)2 heterometallic metal–sulfur core.Financial support from the Ministerio de Ciencia e Innovación (MICINN/FEDER) of Spain (Project CTQ2010-15221), the Diputación General de Aragón (E07), and CONSOLIDER INGENIO-2010, Projects MULTICAT (CSD2009-00050) and Factoría de Cristalización (CSD2006-0015) is gratefully acknowledged.Peer Reviewe