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971.
Patrick Wolf Maxence Valla Dr. Aaron J. Rossini Dr. Aleix Comas‐Vives Dr. Francisco Núñez‐Zarur Prof. Dr. Bernard Malaman Dr. Anne Lesage Prof. Dr. Lyndon Emsley Prof. Dr. Christophe Copéret Prof. Dr. Ive Hermans 《Angewandte Chemie (International ed. in English)》2014,53(38):10179-10183
Dynamic nuclear polarization surface enhanced NMR (DNP‐SENS), Mössbauer spectroscopy, and computational chemistry were combined to obtain structural information on the active‐site speciation in Sn‐β zeolite. This approach unambiguously shows the presence of framework SnIV‐active sites in an octahedral environment, which probably correspond to so‐called open and closed sites, respectively (namely, tin bound to three or four siloxy groups of the zeolite framework). 相似文献
972.
Understanding a Host–Guest Model System through 129Xe NMR Spectroscopic Experiments and Theoretical Studies
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Emmanuelle Dubost Jean‐Pierre Dognon Bernard Rousseau Gaëlle Milanole Christophe Dugave Yves Boulard Estelle Léonce Céline Boutin Patrick Berthault 《Angewandte Chemie (International ed. in English)》2014,53(37):9837-9840
Gaining an understanding of the nature of host–guest interactions in supramolecular complexes involving heavy atoms is a difficult task. Described herein is a robust simulation method applied to complexes between xenon and members of a cryptophane family. The calculated chemical shift of xenon caged in a H2O2 probe, as modeled by quantum chemistry with complementary‐orbital, topological, and energy‐decomposition analyses, is in excellent agreement with that observed in hyperpolarized 129Xe NMR spectra. This approach can be extended to other van der Waals complexes involving heavy atoms. 相似文献
973.
Tuning the Guest‐Binding Ability of a Helically Folded Capsule by In Situ Modification of the Aromatic Oligoamide Backbone
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Dr. Guillaume Lautrette Dr. Christophe Aube Dr. Yann Ferrand Dr. Muriel Pipelier Dr. Virginie Blot Dr. Christine Thobie Dr. Brice Kauffmann Prof. Didier Dubreuil Dr. Ivan Huc 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(6):1547-1553
Starting from a previously described aromatic oligoamide helically folded capsule that binds tartaric acid with high affinity and diastereoselectivity, we demonstrate the feasibility of the direct in situ modification of the helix backbone, which results in a conformational change that reduces its affinity for guests by two orders of magnitude. Specifically, ring contraction of the central pyridazine unit into a pyrrole in the full helical sequence was investigated by using electrochemical and chemical processes. The sequence containing the pyrrole was synthesized independently in a convergent manner to ascertain its structure. The conformation of the pyrrolic folded capsule was elucidated in the solid state by X‐ray crystallography and in solution by using 1H and 13C NMR spectroscopy. Solution studies revealed an unanticipated solvent‐dependent equilibrium between the anti–anti and syn–syn conformations of the pyrrole ring with respect to its two adjacent pyridine units. Titrations of the pyrrole‐containing sequence monitored by 1H NMR spectroscopy confirmed the expected drop in affinity for tartaric acid and malic acid that arises from the conformation change in the backbone that follows the replacement of the pyridazine by a pyrrole. The reduction of the pyridazine to a pyrrole was characterized by cyclic voltammetry both on the entire sequence and on a shorter precursor. The lower cathodic potential of the precursor made its preparative‐scale electroreduction possible. Direct in situ modification of the pyridazine within the entire capsule sequence was achieved chemically by using zinc in acetic acid. 相似文献
974.
Dr. Elisabet Öberg Dr. Andreas Orthaber Dr. Christophe Lescop Prof. Régis Réau Prof. Muriel Hissler Prof. Sascha Ott 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(27):8421-8432
Phosphole‐substituted phosphaalkenes (PPAs) of the general formula Mes*P?C(CH3)?(C4H2P(Ph))?R 5 a – c (Mes*=2,4,6‐tBu3Ph; R=2‐pyridyl ( a ), 2‐thienyl ( b ), phenyl ( c )) have been prepared from octa‐1,7‐diyne‐substituted phosphaalkenes by utilizing the Fagan–Nugent route. The presence of two differently hybridized phosphorus centers (σ2,λ3 and σ3,λ3) in 5 offers the possibility to selectively tune the HOMO–LUMO gap of the compounds by utilizing the different reactivity of the two phosphorus heteroatoms. Oxidation of 5 a – c by sulfur proceeds exclusively at the σ3,λ3‐phosphorus atom, thus giving rise to the corresponding thioxophospholes 6 a – c . Similarly, 5 a is selectively coordinated by AuCl at the σ3,λ3‐phosphorus atom. Subsequent second AuCl coordination at the σ2,λ3‐phosphorus heteroatom results in a dimetallic species that is characterized by a gold–gold interaction that provokes a change in π conjugation. Spectroscopic, electrochemical, and theoretical investigations show that the phosphaalkene and the phosphole both have a sizable impact on the electronic properties of the compounds. The presence of the phosphaalkene unit induces a decrease of the HOMO–LUMO gap relative to reference phosphole‐containing π systems that lack a P?C substituent. 相似文献
975.
Morton Raban Christophe P. Moulin Sanford K. Lauderback Brian Swilley 《Tetrahedron letters》1984,25(32):3419-3422
The absolute configurations of chiral primary amines can be determined using the optical rotations of the corresponding N-p-toluenesulfonyl-N-2,4-dinitrobenzensulfenyl derivatives. 相似文献
976.
Edward Beaumont Jean‐Christophe Lambry Dr. Anne‐Claire Robin Pavel Martasek Prof. Mireille Blanchard‐Desce Dr. Anny Slama‐Schwok Dr. 《Chemphyschem》2008,9(16):2325-2331
We have recently designed a nanotrigger (NT), a photoactive molecule addressing the NADPH sites of proteins. This nanotrigger has a 103 times larger two‐photon cross‐section compared to the ubiquitous NADPH cofactor. In this work, we tested whether two‐photon excitation of the bound NT to NADPH sites may be used to initiate enzymatic catalysis by appropriate electron injection. To establish proof of principle, we monitored the ultrafast absorption of NT bound to the fully active endothelial NO‐Synthase (eNOS) following excitation by one and two‐photons at 405 and 810 nm, respectively. Electron injection from NT* to FAD in eNOS initiated the catalytic cycle in 15±3 ps at both exciting wavelengths. The data proved for the first time that electron transfer can be promoted by two‐photon excitation. We also show that the nanotrigger decays faster in homogeneous solvents than in the NADPH site of proteins, suggesting that hindered environments modified the natural decay of NT. The nanotrigger provides a convenient way of synchronizing an ensemble of proteins in solution with a femtosecond laser pulse. The ability of NT to initiate NOS catalysis by two‐photon excitation may be exploited for controlled and localized release of free NO in cells with enhanced spatial and temporal resolution. 相似文献
977.
Sylvain Gaillard Cédric Fischmeister Christophe M. Thomas Jean-Luc Renaud 《Tetrahedron letters》2008,49(21):3471-3474
A convenient route for the synthesis of a variety of amino-bispyridyl compounds is introduced. Bispyridylamines were prepared in three steps from commercially available 2,6-dibromopyridine, via a copper mediated alkylation followed by two consecutive N-arylation reactions catalyzed by copper and palladium, respectively. 相似文献
978.
Filip De Baerdemaeker Milan Šimek Christophe Leys Willy Verstraete 《Plasma Chemistry and Plasma Processing》2007,27(4):473-485
Among the configurations to generate plasma in electrically conductive liquids only the diaphragm and the capillary discharge
schemes allow to generate plasma which is not in contact with one of the electrodes. Based on this concept, this work reports
for the first time the development of an underwater plasma pump, in which the periodic electrical breakdown inside an asymmetrical
(sub-)millimetre hole results in a net flow of aqueous solution through the hole without the use of any moving parts such
as valves or diaphragms typically used in micropumps. Certain capillary geometries feature very stable flow rates and even
allow altering flow direction by changing the power. By varying the hole’s dimensions, the range of time-independent flow
rates covers more than one order of magnitude and as the discharge produces some of the strongest oxidants available, we believe
that this concept might find application in fields as water decontamination and sterilization. 相似文献
979.
980.