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71.
72.
Organozinc Pivalate Reagents: Segregation,Solubility, Stabilization,and Structural Insights 下载免费PDF全文
Dr. Alberto Hernán‐Gómez Emma Herd Prof. Eva Hevia Dr. Alan R. Kennedy Prof. Dr. Paul Knochel Prof. Dr. Konrad Koszinowski Sophia M. Manolikakes Prof. Robert E. Mulvey Christoph Schnegelsberg 《Angewandte Chemie (International ed. in English)》2014,53(10):2706-2710
The pivalates RZnOPiv?Mg(OPiv)X?n LiCl (OPiv=pivalate; R=aryl; X=Cl, Br, I) stand out amongst salt‐supported organometallic reagents, because apart from their effectiveness in Negishi cross‐coupling reactions, they show more resistance to attack by moist air than conventional organometallic compounds. Herein a combination of synthesis, coupling applications, X‐ray crystallographic studies, NMR (including DOSY) studies, and ESI mass spectrometric studies provide details of these pivalate reagents in their own right. A p‐tolyl case system shows that in [D8]THF solution these reagents exist as separated Me(p‐C6H4)ZnCl and Mg(OPiv)2 species. Air exposure tests and X‐ray crystallographic studies indicate that Mg(OPiv)2 enhances the air stability of aryl zinc species by sequestering H2O contaminants. Coupling reactions of Me(p‐C6H4)ZnX (where X=different salts) with 4‐bromoanisole highlight the importance of the presence of Mg(OPiv)2. Insight into the role of LiCl in these multicomponent mixtures is provided by the molecular structure of [(THF)2Li2(Cl)2(OPiv)2Zn]. 相似文献
73.
Electronic and Structural Properties of Highly Aluminum Ion Doped TiO2 Nanoparticles: A Combined Experimental and Theoretical Study 下载免费PDF全文
Desireé M. de los Santos Teresa Aguilar Dr. Antonio Sánchez‐Coronilla Dr. Javier Navas Dr. Norge Cruz Hernández Dr. Rodrigo Alcántara Dr. Concha Fernández‐Lorenzo Prof.Dr. Joaquín Martín‐Calleja 《Chemphyschem》2014,15(11):2267-2280
This study presents the experimental and theoretical study of highly internally Al‐doped TiO2 nanoparticles. Two synthesis methods were used and detailed characterization was performed. There were differences in the doping and the crystallinity, but the nanoparticles synthesized with the different methods share common features. Anatase to rutile transformation occurred at higher temperatures with Al doping. X‐ray photoelectron spectroscopy showed the generation of oxygen vacancies, which is an interesting feature in photocatalysis. In turn, the band‐gap energy and the valence band did not change appreciably. Periodic density functional calculations were performed to model the experimentally doped structures, the formation of the oxygen vacancies, and the band gap. Calculation of the density of states confirmed the experimental band‐gap energies. The theoretical results confirmed the presence of Ti4+ and Al3+. The charge density study and electron localization function analysis indicated that the inclusion of Al in the anatase structure resulted in a strengthening of the Ti?O bonds around the vacancy. 相似文献
74.
Inside Cover: Quinone‐Rich Poly(dopamine) Magnetic Nanoparticles for Biosensor Applications (ChemPhysChem 17/2014) 下载免费PDF全文
75.
Susana Araceli Carrizales Álvarez Anna Ilyina Karla Monzerratt Gregorio Jáuregui José Luis Martínez Hernández Brenda Berenice Vazquez Gutiérrez Elda Patricia Segura Ceniceros Alejandro Zugasti Cruz Hened Saade Caballero Raúl Guillermo López Campos 《Applied biochemistry and biotechnology》2014,174(5):1945-1958
Avian influenza viruses preferentially bind to sialic acid alpha-2,3-galactose (N-SA-α-2,3-Gal) receptors on epithelial cells. Herein, we describe a procedure we have developed for isolation of N-SA-α-2,3-Gal receptors from porcine trachea using magnetic nanoparticles (NPs) coated with chitosan (NP-Ch) and functionalized with Maackia amurensis lectin (NP-lectin). Magnetic nanoparticles were coated with chitosan in a one-step co-precipitation, and then M. amurensis lectin was immobilized covalently using glutaraldehyde. Lectin coated nanoparticles were incubated with sialic acid enriched fraction of tracheal homogenate, and N-SA-α-2,3-Gal receptor was extracted under magnetic field in two cycles. The presence of 66.4 kDa protein was determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The interaction of immobilized receptor (NP-Ch-R) with M. amurensis lectin (NP-Ch-R-L) was demonstrated by Fourier transform infrared spectrometry (FTIR) and thermogravimetric analysis (TGA). 相似文献
76.
Christian Schumacher Dr. José G. Hernández Prof. Dr. Carsten Bolm 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(38):16499-16502
The formation and regeneration of active CuI species is a fundamental mechanistic step in copper-catalyzed atom transfer radical cyclizations (ATRC). Typically, the presence of the catalytically active CuI species in the reaction mixture is secured by using high CuI catalyst loadings or the addition of complementary reducing agents. In this study it is demonstrated how the piezoelectric properties of barium titanate (BaTiO3) can be harnessed by mechanical ball milling to induce electrical polarization in the strained piezomaterial. This strategy enables the conversion of mechanical energy into electrical energy, leading to the reduction of a CuII precatalyst into the active CuI species in copper-catalyzed mechanochemical solvent-free ATRC reactions. 相似文献
77.
Jennifer Paola Hernández Mancera Francisco Núñez-Zarur Soledad Gutiérrez-Oliva Alejandro Toro-Labbé Ricardo Vivas-Reyes 《Journal of computational chemistry》2020,41(23):2022-2032
Quantum chemical calculations were used to study the mechanism of Diels-Alder reactions involving chiral anthracenes as dienes and a series of dienophiles. The reaction force analysis was employed to obtain a detailed scrutiny of the reaction mechanisms, it has been found that thermodynamics and kinetics of the reactions are quite consistent: the lower the activation energy, the lower the reaction energy, thus following the Bell-Evans-Polanyi principle. It has been found that activation energies are mostly due to structural rearrangements that in most cases represented more than 70% of the activation energy. Electronic activity mostly due to changes in σ and π bonding were revealed by the reaction electronic flux (REF), this property helps identify whether changes on σ or π bonding drive the reaction. Additionally, new global indexes describing the behavior of the electronic activity were introduced and then used to classify the reactions in terms of the spontaneity of their electronic activity. Local natural bond order electronic population analysis was used to check consistency with global REF through the characterization of specific changes in the electronic density that might be responsible for the activity already detected by the REF. Results show that reactions involving acetoxy lactones are driven by spontaneous electronic activity coming from bond forming/strengthening processes; in the case of maleic anhydrides and maleimides it appears that both spontaneous and non-spontaneous electronic activity are quite active in driving the reactions. 相似文献
78.
Daniel Hernández-Valdés Ricardo Fernández-Terán Benjamin Probst Bernhard Spingler Roger Alberto 《Helvetica chimica acta》2020,103(10):e2000147
Reduction of CO2 to CO and H2O is a two electron/two proton process. For this process, multinuclear complexes offer advantages by concentrating reduction equivalents more efficiently than mononuclear systems. We present novel complexes with [Re(η6-C6H6)2]+ as scaffold conjugated to one or two catalytically active [Ru(dmbpy)(CO)2Cl2] subunits (dmbpy=5,5′-dimethyl-2,2′-bipyridine). The [Re(η6-C6H6)2]+ scaffold was chosen due to its very high photo- and chemical stability, as well as the multiple degrees of freedom it offers for any conjugated functionalities. High efficiency and selectivity for the reduction of CO2 to CO (over H2 or HCOOH) is reported. TONs and TOFs were found to be comparable or higher than for the catalyst subunit without the rhenium framework. Cooperativity in photo- and electrocatalysis is observed for the complex comprising two catalytic subunits. The synergistic communication between the two catalytic subunits is responsible for the observed enhancement in both photo- and electrocatalytic performance. Confirmation of electronic communication between the two [Ru(dmbpy)(CO)2Cl2] subunits as well as the elucidation of a possible mechanism was supported by electrochemistry, IR-spectroelectrochemistry and DFT studies. 相似文献
79.
Liquid chromatography with ultraviolet absorbance detection for the analysis of tetracycline residues in honey 总被引:5,自引:0,他引:5
Viñas P Balsalobre N López-Erroz C Hernández-Córdoba M 《Journal of chromatography. A》2004,1022(1-2):125-129
The separation of tetracyclines (TCs) using reversed-phase liquid chromatography (LC) is proposed. The use of an amide-based stationary phase prevents the interaction of tetracyclines with the residual silanol groups and thus avoids the appearance of tailed peaks. Detection was based on using an UV spectrophotometer and gradient elution with acetonitrile-oxalic acid as mobile phase permitted good separation of all the peaks. Specificity was demonstrated by the retention characteristics, UV spectra and peak purity index. Linearity, precision, recovery and sensitivity were satisfactory. The procedure was applied to the analysis of tetracycline residues (tetracycline, oxytetracycline (OTC), chlortetracycline (CTC), doxycycline (DC), minocycline (MINO) and methacycline (MTC)) in honey of different types. Extraction involved using a mild acidic solvent containing EDTA to release protein-bound or sugar-bound tetracyclines. For the clean-up step, solid phase extraction using phenyl cartridges was applied. Detection limits in the honey using the proposed procedure are between 15 and 30 ng g(-1), depending on the tetracycline. 相似文献
80.
Pérez-Sirvent C Martínez-Sánchez MJ García-Lorenzo M López-García I Hernández-Córdoba M 《Analytical and bioanalytical chemistry》2007,388(2):495-498
Use of small membrane pumps, instead of peristaltic pumps, to introduce sample and reagent solutions into the spectrometer
has several advantages in atomic fluorescence spectrometric determination of mercury. This simple modification results in
a substantial saving in the time required for the measurements and so 90% of reagent solution volumes and 95% of sample solution
volumes are saved, with a consequent decrease in the volume of waste generated. The sampling frequency is almost tripled,
with no deterioration in sensitivity, which is similar to that obtained by use of peristaltic pumps. The relative standard
deviation for ten consecutive measurements of a 1 μg L−1 mercury solution was approximately 2%.
Figure Small membrane pumps for the atomic fluorescene spectro metric determination of mercury 相似文献