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31.
Heteronuclear NMR Spectroscopy as a Surface‐Selective Technique: A Unique Look at the Hydroxyl Groups of γ‐Alumina. 下载免费PDF全文
Dr. Mostafa Taoufik Dr. Kai C. Szeto Dr. Nicolas Merle Dr. Iker Del Rosal Dr. Laurent Maron Dr. Julien Trébosc Dr. Grégory Tricot Dr. Régis M. Gauvin Dr. Laurent Delevoye 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(14):4038-4046
The surface hydroxyl groups of γ‐alumina dehydroxylated at 500 °C were studied by a combination of one‐ and two‐dimensional homo‐ and heteronuclear 1H and 27Al NMR spectroscopy at high magnetic field. In particular, by harnessing 1H–27Al dipolar interactions, a high selectivity was achieved in unveiling the topology of the alumina surface. The terminal versus bridging character of the hydroxyl groups observed in the 1H magic‐angle spinning (MAS) NMR spectrum was demonstrated thanks to 1H–27Al RESPDOR (resonance‐echo saturation‐pulse double‐resonance). In a further step the hydroxyl groups were assigned to their aluminium neighbours thanks to a {1H}‐27Al dipolar heteronuclear multiple quantum correlation (D‐HMQC), which was used to establish a first coordination map. Then, in combination with 1H–1H double quantum (DQ) MAS, these elements helped to reveal intimate structural features of the surface hydroxyls. Finally, the nature of a peculiar reactive hydroxyl group was demonstrated following this methodology in the case of CO2 reactivity with alumina. 相似文献
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Maria Pia Lenza Iker Oyenarte Dr. Tammo Diercks Jon Imanol Quintana Dr. Ana Gimeno Dr. Helena Coelho Ana Diniz Dr. Francesca Peccati Sandra Delgado Alexandre Bosch Dr. Mikel Valle Dr. Oscar Millet Prof. Dr. Nicola G. A. Abrescia Dr. Asís Palazón Dr. Filipa Marcelo Dr. Gonzalo Jiménez-Osés Prof. Dr. Jesús Jiménez-Barbero Dr. Ana Ardá Dr. June Ereño-Orbea 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(52):23971-23979
The glycan structures of the receptor binding domain of the SARS-CoV2 spike glycoprotein expressed in human HEK293F cells have been studied by using NMR. The different possible interacting epitopes have been deeply analysed and characterized, providing evidence of the presence of glycan structures not found in previous MS-based analyses. The interaction of the RBD 13C-labelled glycans with different human lectins, which are expressed in different organs and tissues that may be affected during the infection process, has also been evaluated by NMR. In particular, 15N-labelled galectins (galectins-3, -7 and -8 N-terminal), Siglecs (Siglec-8, Siglec-10), and C-type lectins (DC-SIGN, MGL) have been employed. Complementary experiments from the glycoprotein perspective or from the lectin's point of view have permitted to disentangle the specific interacting epitopes in each case. Based on these findings, 3D models of the interacting complexes have been proposed. 相似文献
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Merle N Trébosc J Baudouin A Rosal ID Maron L Szeto K Genelot M Mortreux A Taoufik M Delevoye L Gauvin RM 《Journal of the American Chemical Society》2012,134(22):9263-9275
Flame silica was surface-labeled with (17)O, through isotopic enrichment of both siloxanes and silanols. After heat treatment at 200 and 700 °C under vacuum, the resulting partially dehydroxylated silica materials were investigated by high-field solid-state (1)H and (17)O NMR. More specifically, MQ MAS and HMQC sequences were used to probe the (17)O local environment. In a further step, these (17)O-tagged supports were used for the preparation of supported catalysts by reaction with perhydrocarbyl transition metal derivatives (zirconium tetraalkyl, tantalum trisalkyl-alkylidene, and tungsten trisalkyl-alkylidyne complexes). Detailed (17)O 1D and 2D MQ and HMQC MAS NMR studies demonstrate that signals in the Si-OH, Si-O-Si, and Si-O-metal regions are highly sensitive to local structural modifications, thanks to (17)O wide chemical shift and quadrupolar constant ranges. Experimental results were supported by DFT calculations. From the selective surface labeling, unprecedented information on interactions between supported catalysts and their inorganic carrier has been extracted. 相似文献
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I León EJ Cocinero J Millán AM Rijs I Usabiaga A Lesarri F Castaño JA Fernández 《The Journal of chemical physics》2012,137(7):074303
Propofol (2,6-di-isopropylphenol) is probably the most widely used general anesthetic. Previous studies focused on its complexes containing 1 and 2 water molecules. In this work, propofol clusters containing three water molecules were formed using supersonic expansions and probed by means of a number of mass-resolved laser spectroscopic techniques. The 2-color REMPI spectrum of propofol[middle dot](H(2)O)(3) contains contributions from at least two conformational isomers, as demonstrated by UV/UV hole burning. Using the infrared IR/UV double resonance technique, the IR spectrum of each isomer was obtained both in ground and first excited electronic states and interpreted in the light of density functional theory (DFT) calculations at M06-2X/6-311++G(d,p) and B3LYP/6-311++G(d,p) levels. The spectral analysis reveals that in both isomers the water molecules are forming cyclic hydrogen bond networks around propofol's OH moiety. Furthermore, some evidences point to the existence of isomerization processes, due to a complicated conformational landscape and the existence of multiple paths with low energy barriers connecting the different conformers. Such processes are discussed with the aid of DFT calculations. 相似文献
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Ohashi M Konkol M Del Rosal I Poteau R Maron L Okuda J 《Journal of the American Chemical Society》2008,130(22):6920-6921
A trinuclear rare-earth metal hydride complex was synthesized from the dialkyl complex supported by a monoanionic [NNNN] macrocycle and shown to catalyze the hydrosilylation of olefins efficiently. 相似文献
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Dr. Iker León Dr. Judith Millán Prof. Fernando Castaño Dr. José A. Fernández 《Chemphyschem》2012,13(17):3819-3826
Propofol (2,6‐diisopropylphenol, PPF) homodimers and their complexes with one water molecule are analyzed by means of mass‐resolved excitation spectroscopy. Using two‐color resonance‐enhanced multiphoton ionization (REMPI) the S1 electronic spectra of these systems are obtained, avoiding fragmentation. Due to the large size of these species, the spectra present a large abundance of lines. Using UV/UV hole‐burning spectroscopy, two isomers of PPF2 are found and the existence of at least three isomers for propofol2(H2O)1 (PPF2W1) is demonstrated. Comparison with the structures calculated at the M06‐2X/6‐311++G(d,p) and M06‐2X/6‐31+G(d) levels of theory shows that the main driving forces in PPF2 are several C? H???π interactions accompanied by dipole–dipole interaction between the OH moieties. On the other hand, there is evidence for the formation of cyclic hydrogen‐bond structures in the heterotrimers. A comparison of the results obtained herein with those of similar systems from previously published studies follows. 相似文献
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Cover Picture: Heteronuclear NMR Spectroscopy as a Surface‐Selective Technique: A Unique Look at the Hydroxyl Groups of γ‐Alumina. (Chem. Eur. J. 14/2014) 下载免费PDF全文
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Marcos Juanes Imanol Usabiaga Iker Len Luca Evangelisti Jos A. Fernndez Alberto Lesarri 《Angewandte Chemie (International ed. in English)》2020,59(33):14081-14085
The cyclohexanol homodimer acts as a delicate test model of the role of dispersion forces in intermolecular association. Whereas phenol produces a single dimer, the suppression of π interactions and the larger conformational flexibility in cyclohexanol results in multiple isomerism, with six competing dimers of the free molecule being observed in a supersonic jet expansion. Rotational spectroscopy reveals accurate structural data, specifically the formation of homo‐ and heterochiral diastereoisomers and the presence of both equatorial and axial forms in the dimers. Four dispersion‐corrected density‐functional molecular orbital calculations were tested against the experiment, with B3LYP‐D3(BJ) offering good structural reproducibility with an Alrich's triple‐ζ basis set. However, the prediction of the dimer energetics is largely model‐dependent, thus offering a testbed for the validation of dispersion‐corrected computational models. 相似文献