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991.
Development of CN Coupling Using Mechanochemistry: Catalytic Coupling of Arylsulfonamides and Carbodiimides 下载免费PDF全文
Davin Tan Cristina Mottillo Athanassios D. Katsenis Dr. Vjekoslav Štrukil Prof. Dr. Tomislav Friščić 《Angewandte Chemie (International ed. in English)》2014,53(35):9321-9324
Reported herein is the mechanochemical synthesis of sulfonyl guanidines, a family of molecules which are relevant as pharmaceuticals and herbicides, by direct coupling of sulfonamides and aromatic or aliphatic carbodiimides. Attempts to conduct the coupling in solution have either failed or given very low conversions, thus demonstrating mechanochemistry as the necessary component for the discovery of this synthetic strategy. 相似文献
992.
Dr. Luminita Marin Dr. Simona Moraru Dr. Maria‐Cristina Popescu Alina Nicolescu Cristina Zgardan Prof. Dr. Bogdan C. Simionescu Dr. Mihail Barboiu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(16):4814-4821
An investigation of the constitutional adaptive gelation process of chitosan/cinnamaldehyde ( C / Cy ) dynagels is reported. These gels generate timely variant macroscopic organization across extended scales. In the first stage, imine‐bond formation takes place “in‐water” and generates low‐ordered hydrogels. The progressive formation of imine bonds further induces “ out‐of‐water” increased reactivity within interdigitated hydrophobic self‐assembled layers of Cy , with a protecting environmental effect against hydrolysis and that leads to the stabilization of the imine bonds. The hydrophobic swelling due to Cy layers at the interfaces reaches a critical step when lamellar self‐organized hybrids are generated (24 hours). This induces an important restructuration of the hydrogels on the micrometric scale, thus resulting in the formation of highly ordered microporous xerogel morphologies of high potential interest for chemical separations, drug delivery, and sensors. 相似文献
993.
Single‐Molecule‐Magnet Behavior in the Family of [Ln(OETAP)2] Double‐Decker Complexes (Ln=Lanthanide,OETAP=Octa(ethyl)tetraazaporphyrin) 下载免费PDF全文
Nelson Giménez‐Agulló Dr. Cristina Sáenz de Pipaón Louis Adriaenssens Dr. Marta Filibian Marta Martínez‐Belmonte Eduardo C. Escudero‐Adán Prof. Pietro Carretta Prof. Pablo Ballester Prof. José Ramón Galán‐Mascarós 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(40):12817-12825
Double‐decker complexes of lanthanide cations can be readily prepared with tetraazaporphyrins (porphyrazines). We have synthesized and characterized a series of neutral double‐decker complexes [Ln(OETAP)2] (Ln=Tb3+, Dy3+, Gd3+, Y3+; OETAP=octa(ethyl)tetraazaporphyrin). Some of these complexes show analogous magnetic features to their phthalocyanine (Pc) counterparts. The Tb3+ and Dy3+ derivatives exhibit single‐molecule magnet (SMM) behavior with high blocking temperatures over 50 and 10 K, respectively. These results confirm that, in double‐decker complexes that involve Tb or Dy, the (N4)2 square antiprism coordination mode has an important role in inducing very large activation energies for magnetization reversal. In contrast with their Pc counterparts, the use of tetraazaporphyrin ligands endows the presented [Ln(OETAP)2] complexes with extraordinary chemical versatility. The double‐decker complexes that exhibit SMM behavior are highly soluble in common organic solvents, and easily processable even through sublimation. 相似文献
994.
Maura Brioschi Sonia Eligini Mauro Crisci Susanna Fiorelli Elena Tremoli Susanna Colli Cristina Banfi 《Analytical and bioanalytical chemistry》2014,406(12):2817-2825
This paper describes a microproteomic workflow that is useful for simultaneously identifying and quantifying proteins from a minimal number of morphotypically heterogeneous cultured adherent cells. The analytical strategy makes use of laser capture microdissection, an effective means of harvesting pure cell populations, and label-free mass spectrometry. We optimised the workflow with particular reference to cell fixation which is crucial for successful laser-based microdissection and also downstream molecular studies. In addition, we defined the minimum number of cells to be isolated and analysed for satisfactory proteome coverage. To set up this workflow, we choose human monocyte-derived macrophages spontaneously differentiated in vitro. These cells, under our culture conditions, show distinct morphotypes, reminiscent of the heterogeneity observed in tissues in various homeostatic and pathological states, e.g. atherosclerosis. This optimised workflow may provide new insights into biology and pathology of heterogeneous cell in culture, particularly when other cell selection approaches are not suitable. Figure
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995.
Cristina Ruiz-Samblás José M. Cadenas David A. Pelta Luis Cuadros-Rodríguez 《Analytical and bioanalytical chemistry》2014,406(11):2591-2601
The aim of this article is to study tree-based ensemble methods, new emerging modelling techniques, for authentication of samples of olive oil blends to check their suitability for classifying the samples according to the type of oil used for the blend as well as for predicting the amount of olive oil in the blend. The performance of these methods has been investigated in chromatographic fingerprint data of olive oil blends with other vegetable oils without needing either to identify or to quantify the chromatographic peaks. Different data mining methods—classification and regression trees, random forest and M5 rules—were tested for classification and prediction. In addition, these classification and regression tree approaches were also used for feature selection prior to modelling in order to reduce the number of attributes in the chromatogram. The good outcomes have shown that these methods allow one to obtain interpretable models with much more information than the traditional chemometric methods and provide valuable information for detecting which vegetable oil is mixed with olive oil and the percentage of oil used, with a single chromatogram. Figure
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996.
Cristina Gonzalez-Gago Petr Smid Thomas Hofmann Cornel Venzago Volker Hoffmann Wolfgang Gruner 《Analytical and bioanalytical chemistry》2014,406(29):7473-7482
The performance of glow discharge optical emission spectroscopy and mass spectrometry for oxygen determination is investigated using a set of new conductive samples containing oxygen in the percent range in three different matrices (Al, Mg, and Cu) prepared by a sintering process. The sputtering rate corrected calibrations obtained at standard conditions for the 4 mm anode (700 V, 20 mA) in GD-OES are matrix independent for Mg and Al but not for Cu. The importance of a “blue shifted” line of oxygen at 130.22 nm (first reported by Köster) for quantitative analyses by GD-OES is confirmed. Matrix-specific calibrations for oxygen in GD-MS are presented. Two source concepts—fast flow (ELEMENT GD) and low gas flow (VG9000)—are evaluated obtaining higher sensitivity with the static flow source. Additional experiments using Ar-He mixtures or μs pulsed GD are carried out in ELEMENT GD aiming to improve the oxygen sensitivity. 相似文献
997.
David K. Geiger H. Cristina Geiger Jared M. Deck 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(12):1125-1132
The synthesis and structural characterization of 2‐(furan‐2‐yl)‐1‐(furan‐2‐ylmethyl)‐1H‐benzimidazole [C16H12N2O2, (I)], 2‐(furan‐2‐yl)‐1‐(furan‐2‐ylmethyl)‐1H‐benzimidazol‐3‐ium chloride monohydrate [C16H13N2O2+·Cl−·H2O, (II)] and the hydrobromide salt 5,6‐dimethyl‐2‐(furan‐2‐yl)‐1‐(furan‐2‐ylmethyl)‐1H‐benzimidazol‐3‐ium bromide [C18H17N2O2+·Br−, (III)] are described. Benzimidazole (I) displays two sets of aromatic interactions, each of which involves pairs of molecules in a head‐to‐tail arrangement. The first, denoted set (Ia), exhibits both intermolecular C—H...π interactions between the 2‐(furan‐2‐yl) (abbreviated as Fn) and 1‐(furan‐2‐ylmethyl) (abbreviated as MeFn) substituents, and π–π interactions involving the Fn substituents between inversion‐center‐related molecules. The second, denoted set (Ib), involves π–π interactions involving both the benzene ring (Bz) and the imidazole ring (Im) of benzimidazole. Hydrated salt (II) exhibits N—H...OH2...Cl hydrogen bonding that results in chains of molecules parallel to the a axis. There is also a head‐to‐head aromatic stacking of the protonated benzimidazole cations in which the Bz and Im rings of one molecule interact with the Im and Fn rings of adjacent molecules in the chain. Salt (III) displays N—H...Br hydrogen bonding and π–π interactions involving inversion‐center‐related benzimidazole rings in a head‐to‐tail arrangement. In all of the π–π interactions observed, the interacting moieties are shifted with respect to each other along the major molecular axis. Basis set superposition energy‐corrected (counterpoise method) interaction energies were calculated for each interaction [DFT, M06‐2X/6‐31+G(d)] employing atomic coordinates obtained in the crystallographic analyses for heavy atoms and optimized H‐atom coordinates. The calculated interaction energies are −43.0, −39.8, −48.5, and −55.0 kJ mol−1 for (Ia), (Ib), (II), and (III), respectively. For (Ia), the analysis was used to partition the interaction energies into the C—H...π and π–π components, which are 9.4 and 24.1 kJ mol−1, respectively. Energy‐minimized structures were used to determine the optimal interplanar spacing, the slip distance along the major molecular axis, and the slip distance along the minor molecular axis for 2‐(furan‐2‐yl)‐1H‐benzimidazole. 相似文献
998.
Cristina Nú?ez Sergio M Santos Elisabete Oliveira Hugo M Santos José Luis Capelo Carlos Lodeiro 《ChemistryOpen》2014,3(5):190-198
A new bipyridyl derivative 1 bearing rhodamine B as visible fluorophore was designed, synthesized and characterized as a fluorescent and colorimetric sensor for metal ions. Interaction with Cu2+, Zn2+, Cd2+, Hg+, and Hg2+ ions was followed by UV/Vis and emission spectroscopy. Upon addition of these metal ions, different colorimetric and fluorescent responses were observed. “Off-on-off” (Cu2+, Zn2+, and Hg2+) and “off-on” (Hg+ and Cd2+) systems were obtained. Probe 1 was explored to mimic XOR and OR logic operations for the simultaneous detection of Hg+–Cu2+ and Hg+–Zn2+ pairs, respectively. DFT calculations were also performed to gain insight into the lowest-energy gas-phase conformation of free receptor 1 as well as the atomistic details of the coordination modes of the various metal ions. 相似文献
999.
Gonçalo Graça Ana Sofia Moreira Ana João V. Correia Brian J. Goodfellow António S. Barros Iola F. Duarte Isabel M. Carreira Eulália Galhano Cristina Pita Maria do Céu Almeida Ana M. Gil 《Analytica chimica acta》2013
This work describes a mid-infrared (MIR) metabolic profiling study of 2nd trimester amniotic fluid in relation to selected prenatal disorders, with results focusing on fetal malformations (FM), preterm delivery (PTD) and premature rupture of membranes (PROM), the latter two conditions occurring later in pregnancy. Partial least squares-discriminant analysis (PLS-DA) models were obtained for FM and pre-PTD subject groups, supported by Monte Carlo Cross Validation (MCCV), and identified specific MIR profile changes. For pre-PROM subjects, minor changes were noted. MIR interpretation was assisted by intra- (MIR/MIR) and inter- (MIR/NMR) domain statistical correlation analysis, the results unveiling possible biomarker MIR signatures for FM and pre-PTD subjects. Biofluid MIR metabolic profiling holds enticing possibilities as a low cost, easy to use, rapid method and the results presented have shown its sensitivity to clinically diagnosed conditions such as FM, and to the pre-clinical stages of PTD. Specific improvement needs are discussed, namely regarding sample numbers and experimental reproducibility. 相似文献
1000.
Marta F. T. Ribeiro Cristina M. C. M. Couto Pedro M. M. Conceição João L. M. Santos 《Analytical letters》2013,46(11):1769-1778
In this work, an automated multipumping pulsed flow system was implemented for the determination of phosphate in natural waters. The developed flow approach was based on the spectrophotometric determination of phosphate by using the vanadomolybdate reaction. The exploitation of a very simple manifold configuration relying on the utilization of just two active components, in this case two solenoid actuated micropumps that were accountable for sample and reagent insertion and commutation, reaction zone formation, and solutions propelling, provided a great operational and optimization simplicity, low reagent consumption, and waste minimization. Linear calibration plots for phosphate concentrations of up to 20 mg L?1 (R2 = 0.999, n = 6) were obtained, with a detection limit of 0.2 mg L?1. The sampling rate was about 60 samples per hour. The system was applied to the monitoring of phosphate in local streams at specific sampling stations. 相似文献