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151.
Insertion of a Single‐Molecule Magnet inside a Ferromagnetic Lattice Based on a 3D Bimetallic Oxalate Network: Towards Molecular Analogues of Permanent Magnets 下载免费PDF全文
Dr. Miguel Clemente‐León Prof. Eugenio Coronado Prof. Carlos J. Gómez‐García Dr. Maurici López‐Jordà Dr. Agustín Camón Ana Repollés Dr. Fernando Luis 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(6):1669-1676
The insertion of the single‐molecule magnet (SMM) [MnIII(salen)(H2O)]22+ (salen2?=N,N′‐ethylenebis‐(salicylideneiminate)) into a ferromagnetic bimetallic oxalate network affords the hybrid compound [MnIII(salen)(H2O)]2[MnIICrIII(ox)3]2 ? (CH3OH) ? (CH3CN)2 ( 1 ). This cationic Mn2 cluster templates the growth of crystals formed by an unusual achiral 3D oxalate network. The magnetic properties of this hybrid magnet are compared with those of the analogous compounds [MnIII(salen)(H2O)]2[ZnIICrIII(ox)3]2 ? (CH3OH) ? (CH3CN)2 ( 2 ) and [InIII(sal2‐trien)][MnIICrIII(ox)3] ? (H2O)0.25 ? (CH3OH)0.25 ? (CH3CN)0.25 ( 3 ), which are used as reference compounds. In 2 it has been shown that the magnetic isolation of the Mn2 clusters provided by their insertion into a paramagnetic oxalate network of CrIII affords a SMM behavior, albeit with blocking temperatures well below 500 mK even for frequencies as high as 160 kHz. In 3 the onset of ferromagnetism in the bimetallic MnIICrIII network is observed at Tc=5 K. Finally, in the hybrid compound 1 the interaction between the two magnetic networks leads to the antiparallel arrangement of their respective magnetizations, that is, to a ferrimagnetic phase. This coupling induces also important changes on the magnetic properties of 1 with respect to those of the reference compounds 2 and 3 . In particular, compound 1 shows a large magnetization hysteresis below 1 K, which is in sharp contrast with the near‐reversible magnetizations that the SMMs and the oxalate ferromagnetic lattice show under the same conditions. 相似文献
152.
Ricardo Molina Miguel Gómez Chi-Wai Kan Enric Bertran 《Cellulose (London, England)》2014,21(1):729-739
Materials with hydrophilic–oleophobic properties are of relevance due to their application to different fields such as self-cleaning coatings, liquid–liquid separation membranes and functional textiles for different technical applications. In this work, hydrophilic–oleophobic coatings have been deposited on cellulosic materials (filter paper and bleached cotton) by means of plasma assisted polymerization of acrylic acid solutions in water followed by cationic fluorosurfactant complexation. Chemical composition of the coatings on cellulosic materials was characterized by means of FTIR–ATR and XPS whereas their morphology was studied by SEM. Hydrophilic–oleophobic behavior was characterized by means of contact angle and wetting time. Additionally wetting properties of cationic, anionic and non-ionic surfactant solutions on the hydrophilic–oleophobic coatings were used to characterize the polyelectrolyte electrostatic forces upon the functionalized layer. 相似文献
153.
Dr. Miguel Paraja Prof. Stefan Matile 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(15):6332-6336
The concept of anion–π catalysis focuses on the stabilization of anionic transition states on aromatic π surfaces. Recently, we demonstrated the occurrence of epoxide-opening ether cyclizations on aromatic π surfaces. Although the reaction proceeded through unconventional mechanisms, the obtained products are the same as those from conventional Brønsted acid catalysis, and in agreement with the Baldwin selectivity rules. Different mechanisms, however, should ultimately lead to new products, a promise anion–π catalysis has been reluctant to live up to. Herein, we report non-trivial reactions that work with anion–π catalysis, but not with Brønsted acids, under comparable conditions. Namely, we show that the anion–π templated autocatalysis and epoxide opening with alcoholate–π interactions can provide access to unconventional ring chemistry. For smaller rings, anion–π catalysis affords anti-Baldwin oxolanes, 2-oxabicyclo[3.3.0]octanes, and the expansion of Baldwin oxetanes by methyl migration. For larger rings, anion–π templated autocatalysis is thought to alleviate the entropic penalty of folding to enable disfavored anti-Baldwin cyclizations into oxepanes and oxocanes. 相似文献
154.
Joan Miguel‐vila María Toms‐Gamasa Jos L. Mascareas 《Angewandte Chemie (International ed. in English)》2020,59(40):17628-17633
Metal‐mediated intracellular reactions are becoming invaluable tools in chemical and cell biology, and hold promise for strongly impacting the field of biomedicine. Most of the reactions reported so far involve either uncaging or redox processes. Demonstrated here for the first time is the viability of performing multicomponent alkyne cycloaromatizations inside live mammalian cells using ruthenium catalysts. Both fully intramolecular and intermolecular cycloadditions of diynes with alkynes are feasible, the latter providing an intracellular synthesis of appealing anthraquinones. The power of the approach is further demonstrated by generating anthraquinone AIEgens (AIE=aggregation induced emission) that otherwise do not go inside cells, and by modifying the intracellular distribution of the products by simply varying the type of ruthenium complex. 相似文献
155.
Pablo R. Beltrán Juan Miguel Gil Rafael Rodríguez Guadalupe Espinosa Manuel D. Barriga-Carrasco 《X射线光谱测定》2020,49(1):173-176
The purpose of this work is to study the interaction between an ion beam and a doped deuterium-tritium (DT) plasma in a fast ignition nuclear fusion context. In order to analyze the influence of the dopants in the interaction process, we present a physical model to carry out spatial-temporal simulations of the stopping of an ion beam interacting with a doped plasma target, the plasma heating processes, and the formation of the ignition regions. We perform a set of numerical experiments where different concentrations of dopants are added to a fully ionized DT plasma. These simulations allow us to characterize the increase in the stopping power and the maximum temperatures achieved with the presence of impurities, as well as the reduction of the heated and ignition regions. This reduction in the ignition region indicates difficulties for the formation of an efficient hot spot when there are dopants in the DT plasma. 相似文献
156.
Juan M. Muñoz-Ocaña Ainouna Bouziane Farzeen Sakina Richard T. Baker Ana B. Hungría Jose J. Calvino Antonio M. Rodríguez-Chía Miguel López-Haro 《Particle & Particle Systems Characterization》2020,37(6):2000070
A novel procedure to optimize the 3D morphological characterization of nanomaterials by means of high angle annular dark field scanning-transmission electron tomography is reported and is successfully applied to the analysis of a metal- and halogen-free ordered mesoporous carbon material. The new method is based on a selection of the two parameters (μ and β) which are key in the reconstruction of tomographic series by means of total variation minimization (TVM). The parameter-selected TVM reconstructions obtained using this approach clearly reveal the porous structure of the carbon-based material as consisting of a network of parallel, straight channels of ≈6 nm diameter ordered in a honeycomb-type arrangement. Such an unusual structure cannot be retrieved from a TVM 3D reconstruction using default reconstruction values. Moreover, segmentation and further quantification of the optimized 3D tomographic reconstruction provide values for different textural parameters, such as pore size distribution and specific pore volume that match very closely with those determined by macroscopic physisorption techniques. The approach developed can be extended to other reconstruction models in which the final result is influenced by parameter choice. 相似文献
157.
Alberto Guilln Jos Martínez Juan Miguel Carceller Luis Javier Herrera 《Entropy (Basel, Switzerland)》2020,22(11)
The main goal of this work is to adapt a Physics problem to the Machine Learning (ML) domain and to compare several techniques to solve it. The problem consists of how to perform muon count from the signal registered by particle detectors which record a mix of electromagnetic and muonic signals. Finding a good solution could be a building block on future experiments. After proposing an approach to solve the problem, the experiments show a performance comparison of some popular ML models using two different hadronic models for the test data. The results show that the problem is suitable to be solved using ML as well as how critical the feature selection stage is regarding precision and model complexity. 相似文献
158.
Jos Mahía Miguel A. Maestro Miguel Vzquez Manuel R. Bermejo Ana M. Gonzlez Marcelino Maneiro 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(3):347-348
The structure of the title compound, C30H30N4O4S2, is highly conditioned in the solid state by two strong N—H?N interactions. The values of the distances between the aminic N atoms [5.865 (3) Å] and the iminic N atoms [2.930 (4) Å], in conjunction with the long distance between the S atoms of the two tosyl groups [7.673 (1) Å], suggest that when the molecule acts as a ligand it will provide a single cavity for N4 coordination to the metal centre. 相似文献
159.
Ali Liazid Gerardo F. Barbero Miguel Palma Jamal Brigui Carmelo G. Barroso 《Chromatographia》2007,66(7-8):571-575
Results from a systematic study of the factors affecting extraction of cis-verbenol and verbenone from pine seeds are presented. Five extraction conditions were investigated: extraction solvent, method
of extraction, extraction temperature, volume of solvent, and the ratio of the mass of sample to the amount of extraction
solvent. The resulting optimized method uses magnetic-stirring-assisted extraction of pine seeds (5 g) with ethyl acetate
(75 mL) for 20 min, at room temperature. RSDs were less than 5% for both compounds. GC–FID was used for quantification of
cis-verbenol and verbenone in the extracts. 相似文献
160.
It has been developed an automatic stop-flow procedure for sequential photometric determination of anionic and cationic surfactants in a same sample of water. The flow system was based on multicommutation process that was designed employing two solenoid micro-pumps and six solenoid pinch valves, which under microcomputer control carry out fluid propelling and reagent solutions handling. A homemade photometer using a photodiode as detector and two light emitting diodes (LEDs) with emission at 470 nm (blue) and 650 nm (red) as radiation sources, which was tailored to allow the determination of anionic and cationic surfactants in waters. The procedure for anionic surfactant determination was based on the substitution reaction of methyl orange (MO) by the anionic surfactant sodium dodecylbenzene sulfonate (DBS) to form an ion-pair with the cetyl pyridine chloride (CPC). Features such as a linear response ranging from 0.35 to 10.5 mg L−1 DBS (R = 0.999), a detection limit of 0.06 mg L−1 DBS and a relative standard deviation of 0.6% (n = 11) were achieved. For cationic surfactant determination, the procedure was based on the ternary complex formation between cationic surfactant, Fe(III) and chromazurol S (CAS) using CPC as reference standard solution. A linear response range between 0.34 and 10.2 mg L−1 CPC (R = 0.999), a detection limit of 0.05 mg L−1 CPC and a relative standard deviation of 0.5% (n = 11) were obtained. In both cases, the sampling throughput was 60 determinations per hour. Reagents consumption of 7.8 μg MO, 8.2 μg CPC, 37.2 μg CAS and 21.6 μg Fe(III) per determination were achieved. Analyzing river water samples and applying t-test between the results found and those obtained using reference procedures for both surfactant types provide no significant differences at 95% confidence level. 相似文献