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71.
Prof. Dr. Javier A. Cabeza Dr. Pablo García-Álvarez Prof. Dr. Mar Gómez-Gallego Laura González-Álvarez Alba D. Merinero Prof. Dr. Miguel A. Sierra 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(36):8635-8642
The reactivity of amidinatotetrylenes of the type E(tBu2bzm)R1 (E=Si, Ge; tBu2bzm=N,N′-bis(tertbutyl)benzamidinate; R1=alkyl or aryl) with the chromium Fischer alkynylcarbene complexes [Cr{C(OEt)C2R2}(CO)5] (R2=Ph; ferrocenyl, Fc) has been studied. At room temperature, two different reaction pathways have been identified: (a) attack of the amidinatotetrylene to the alkynyl C2 atom (γ-attack), which leads to σ-allenyl complexes in which the original Ccarbene atom maintains its attachment to the Cr(CO)5 and OEt groups (compounds 3 ), and (b) attack of the amidinatotetrylene to the Ccarbene atom (α-attack), which ends in σ-allenyl complexes in which the original Ccarbene atom is not attached to the metal atom and has been inserted into an E−N bond of the amidinatotetrylene forming an E-C-N-C-N five-membered ring (compounds 4 ). It has been found that compounds 3 are thermodynamically less stable than their corresponding 4 isomers and that some of the former (E=Ge; R1=CH2SiMe3) can be transformed into the latter upon heating. At high temperatures (>70 °C) the reactions involving bulky amidinatotetrylenes (R1=Mes, tBu) end in the carbene-substitution products [Cr{E(tBu2bzm)R1}(CO)5]. 相似文献
72.
Javier Mazzaferri 《Optics Communications》2010,283(10):2056-2060
Multiresolution analysis is very useful for characterization of textures, segmentation tasks, and feature enhancement. The development of optical methods to perform such procedures is highly promissory for real-time applications. Usually, the optical implementations of multiresolution analysis consist in the decomposition of the input scene in different frequency bands, obtaining various filtered versions of the scene. However, under certain circumstances it could be useful to provide just one version of the scene where the different filters are applied in different regions. This procedure could be specially interesting for biological and medical applications in situations when the approximate localization of the scale information is known a priori. In this paper we present a fully optical method to perform multiresolution analysis with spatial localization. By means of the proposed technique, the multi-scale analysis is performed at once in a unique image. The experimental set-up consist of a double-pass convergent optical processor. The first stage of the device allows the multiple band decomposition, while the second stage confines the information of each band to different regions of the object and recombines it to achieve the desired operation. Numerical simulations and experimental results, which prove the very good performance of the method, are presented. 相似文献
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74.
Zaira Domínguez Javier Hernández Lorena Silva-Gutiérrez Magali Salas-Reyes Mario Sánchez Gabriel Merino 《Phosphorus, sulfur, and silicon and the related elements》2013,188(4):772-784
The effect of electron-withdrawing (EW) and electron-releasing (ER) substituents on the 31P NMR chemical shifts and the structural parameters of a series of tris-(p-X-aryl)selenophosphates is reported in this article. Similarly to O-aryl phosphates and O-aryl thiophosphates, EW groups attached to aromatic rings induce a shielding effect on the 31P NMR signal. After a detailed experimental and theoretical analysis, we confirmed that the selenium atom is the main part responsible for the charge density transfer toward phosphorus through a back-bonding effect. The obtained 1JP-Se values for the complete series agree with this observation. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. 相似文献
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Hepcidin-25 has been defined as the key biomarker in iron metabolism. This peptide binds to the iron transporter ferroportin to cause its degradation. Therefore, the need for specific, accurate and precise methods for the quantification of hepcidin-25 in biological fluids is dramatically increasing. In this regard, the use of rapid immunochemical methods that provide low limit of quantification is desired for routine clinical use. However, such fast methodologies should be first analytically evaluated and compared with alternative strategies to check for their advantages and limitations. Here we compare the use of a commercial immunochemical assay for hepcidin determination with a novel analytical approach based on Cu-labeling of the peptide followed by Cu determination using liquid chromatography (HPLC) and plasma mass spectrometry (ICP-MS). The figures of merit of both systems reveal similar analytical characteristics and both seem to be adequate for the determination of the peptide at biologically relevant concentrations in human serum samples. The analysis of a larger number of samples (n = 50) by both techniques showed a good agreement in the concentrations found. Such finding permits to address the hepcidin recovery in the sample preparation procedure necessary for the HPLC-ICP-MS analysis in human serum that turn out to be 76–85%. Additionally, limitations due to cross-reactivity issues of the ELISA method could be addressed in some of the samples by using LC-ICP-MS and were confirmed by LC-Electrospray-MS. 相似文献
78.
Dr. Benjamin J. Coe Dr. Simon P. Foxon Dr. Madeleine Helliwell Dr. Daniela Rusanova Dr. Bruce S. Brunschwig Prof. Dr. Koen Clays Griet Depotter Dr. Marcin Nyk Prof. Dr. Marek Samoc Dominika Wawrzynczyk Prof. Dr. Javier Garín Dr. Jesús Orduna 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(21):6613-6629
New complexes with six ferrocenyl (Fc) groups connected to ZnII or CdII tris(2,2′‐bipyridyl) cores are described. A thorough characterisation of their BPh4? salts includes two single‐crystal X‐ray structures, highly unusual for such species with multiple, extended substituents. Intense, visible d(FeII)→π* metal‐to‐ligand charge‐transfer (MLCT) bands accompany the π→π* intraligand charge‐transfer absorptions in the near UV region. Each complex shows a single, fully reversible FeIII/II wave when probed electrochemically. Molecular quadratic nonlinear optical (NLO) responses are determined by using hyper‐Rayleigh scattering and Stark spectroscopy. The latter gives static first hyperpolarisabilities β0 reaching as high as approximately 10?27 esu and generally increasing with π‐conjugation extension. Z‐scan cubic NLO measurements reveal high two‐photon absorption cross‐sections σ2 of up to 5400 GM in one case. DFT calculations reproduce the π‐conjugation dependence of β0, and TD‐DFT predicts three transitions close in energy contributing to the MLCT bands. The lowest energy transition has octupolar character, whereas the other two are degenerate and dipolar in nature. 相似文献
79.
Javier Benito Mónica García-Mardones Víctor Pérez-Gregorio Ignacio Gascón Carlos Lafuente 《Journal of solution chemistry》2014,43(4):696-710
In this work, thermophysical properties of n-ethylpyridinium bis(trifluoromethylsulfonyl)imide have been studied at atmospheric pressure in the temperature range 288.15–338.15 K. Density, speed of sound, refractive index, surface tension, isobaric molar heat capacity, electrical conductivity and kinematic viscosity have been measured; from these data the isobaric expansibility, isentropic compressibility, molar refraction, entropy and enthalpy of surface formation per unit of surface area, and dynamic viscosity have been calculated. Moreover, we have characterized the thermal behavior of the compound. Results have been analyzed paying special attention to the structural and energetic factors. The magnitude and directionality of the cation–anion interactions have been studied using ab initio quantum calculations, which allow a better understanding of the physicochemical behavior of the ionic liquid. Finally, density values and radial distribution functions were also estimated ab initio from classical molecular dynamics simulations, providing acceptable density predictions. 相似文献
80.
Determination of estrogens in environmental water samples using 1,3‐dipentylimidazolium hexafluorophosphate ionic liquid as extraction solvent in dispersive liquid–liquid microextraction 下载免费PDF全文
Bárbara Socas‐Rodríguez Javier Hernández‐Borges María Asensio‐Ramos Antonio V. Herrera‐Herrera Jose A. Palenzuela Miguel Ángel Rodríguez‐Delgado 《Electrophoresis》2014,35(17):2479-2487
In this work, the potential of a symmetric dialkyl‐substituted ionic liquid (IL), 1,3‐dipenthylimidazolium hexafluorophosphate ([PPIm][PF6]), as extraction solvent in dispersive liquid–liquid microextraction (DLLME) has been studied for the analysis of a group of three natural (estriol, 17β‐estradiol, and 17α‐estradiol) and four synthetic (17α‐ethynylestradiol, diethylstibestrol, dienestrol, and hexestrol) estrogenic compounds as well as one mycotoxin with estrogenic activity (zearalenone) in different types of water samples (Milli‐Q, mineral, and wastewater). Separation, determination, and quantification were developed by HPLC‐DAD and a fluorescence detector (FD) connected in series. Factors influencing the IL‐DLLME procedure (sample pH, amount of IL, type and volume of disperser solvent, ionic strength, and assistance of vortex agitation) were investigated and optimized by means of a step‐by‐step approach. Once the optimum extraction conditions were established (10 mL of water at pH 8, 60 mg of [PPIm][PF6], 500 μL of ACN as disperser solvent and vortex agitation for 1 min), the calibration curves of the whole method (IL‐DLLME‐HPLC‐DAD/FD) were obtained and precision and accuracy were evaluated. It was demonstrated that the developed methodology was repeatable, accurate, and selective with limits of detection in the 0.30–0.57 μg/L and 13.8–37.1 μg/L range for FD and DAD, respectively. Relative recovery values were higher than 85% for the different types of water samples and the Student's t test demonstrated that there were not significant differences between the added and the found concentration. 相似文献