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101.
102.
Gronnier C Kramer S Odabachian Y Gagosz F 《Journal of the American Chemical Society》2012,134(2):828-831
In the presence of a Cu(I) catalyst and a pyridine oxide, alkynyl oxiranes and oxetanes can be converted into functionalized five- or six-membered α,β-unsaturated lactones or dihydrofuranaldehydes. This new oxidative cyclization is proposed to proceed via an unusual allenyloxypyridinium intermediate. 相似文献
103.
Joosten A Trolez Y Collin JP Heitz V Sauvage JP 《Journal of the American Chemical Society》2012,134(3):1802-1809
A new copper-complexed [3]rotaxane consisting of two coordinating 30-membered rings threaded by a two-binding-site axis has been prepared in good yield from relatively simple organic fragments. The main specificity of the system originates from the stoppering reaction, based on "click" chemistry, and thus from the presence of two triazole groups at positions next to the bidentate chelates of the axis central part. The geometry of the coordinating atoms belonging to the axis is such that the triazole groups can either be part of the coordinating fragments when the metal center is 5-coordinate or be not at all involved in coordination to the metal when the latter is 4-coordinate. To be more specific, when the two complexed metal centers are monovalent copper(I) centers, the triazoles are not included in the metal coordination sphere, whereas when the metal centers are Cu(II) or Zn(2+), the triazole groups are bound to the metals. This is easily explained by the fact that Cu(I) is preferably 4-coordinate and Cu(II) and Zn(2+) are 5-coordinate. The interconversion between both situations (4- or 5-coordinate) can be quantitatively induced by metal exchange (Cu(I)/Zn(2+)) or by a redox process (Cu(II)/Cu(I)). It leads to important geometrical changes and in particular to a strong modification of the angle between the two rings. As a consequence, the two threaded rings undergo a motion which is reminiscent of a wing-flapping movement similar to that of birds. This flapping motion is fast and quantitative. It should lead to new functional molecular machines in the future. 相似文献
104.
Chavillon B Cario L Renaud A Tessier F Cheviré F Boujtita M Pellegrin Y Blart E Smeigh A Hammarström L Odobel F Jobic S 《Journal of the American Chemical Society》2012,134(1):464-470
Zinc oxide is considered as a very promising material for optoelectronics. However, to date, the difficulty in producing stable p-type ZnO is a bottleneck, which hinders the advent of ZnO-based devices. In that context, nitrogen-doped zinc oxide receives much attention. However, numerous reviews report the controversial character of p-type conductivity in N-doped ZnO, and recent theoretical contributions explain that N-doping alone cannot lead to p-typeness in Zn-rich ZnO. We report here that the ammonolysis at low temperature of ZnO(2) yields pure wurtzite-type N-doped ZnO nanoparticles with an extraordinarily large amount of Zn vacancies (up to 20%). Electrochemical and transient spectroscopy studies demonstrate that these Zn-poor nanoparticles exhibit a p-type conductivity that is stable over more than 2 years under ambient conditions. 相似文献
105.
FX Gallat AP Brogan Y Fichou N McGrath M Moulin M Härtlein J Combet J Wuttke S Mann G Zaccai CJ Jackson AW Perriman M Weik 《Journal of the American Chemical Society》2012,134(32):13168-13171
The observation of biological activity in solvent-free protein-polymer surfactant hybrids challenges the view of aqueous and nonaqueous solvents being unique promoters of protein dynamics linked to function. Here, we combine elastic incoherent neutron scattering and specific deuterium labeling to separately study protein and polymer motions in solvent-free hybrids. Myoglobin motions within the hybrid are found to closely resemble those of a hydrated protein, and motions of the polymer surfactant coating are similar to those of the hydration water, leading to the conclusion that the polymer surfactant coating plasticizes protein structures in a way similar to hydration water. 相似文献
106.
Dr. Bo Liu Dr. Thierry Roisnel Jean‐Paul Guégan Prof. Jean‐François Carpentier Dr. Yann Sarazin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(20):6289-6301
The factors governing the stability and the reactivity towards cyclic esters of heteroleptic complexes of the large alkaline earth metals (Ae) have been probed. The synthesis and stability of a family of heteroleptic silylamido and alkoxide complexes of calcium [{LOi}Ca? Nu(thf)n] supported by mono‐anionic amino ether phenolate ligands (i=1, {LO1}?=4‐(tert‐butyl)‐2,6‐bis(morpholinomethyl)phenolate, Nu?=N(SiMe2H)2?, n=0, 4 ; i=2, {LO2}?=2,4‐di‐tert‐butyl‐6‐{[2‐(methoxymethyl)pyrrolidin‐1‐yl]methyl}phenolate, Nu?=N(SiMe2H)2?, n=0, 5 ; i=4, {LO4}?=2‐{[bis(2‐methoxyethyl)amino]methyl}‐4,6‐di‐tert‐butylphenolate, Nu?=N(SiMe2H)2?, n=1, 6 ; Nu?=HC?CCH2O?, n=0, 7 ) and those of the related [{LO3}Ae? N(SiMe2H)2] ({LO3}?=2‐[(1,4,7,10‐tetraoxa‐13‐azacyclopentadecan‐13‐yl)methyl]‐4,6‐di‐tert‐butylphenolate Ae=Ca, 1 ; Sr, 2 ; Ba, 3 ) have been investigated. The molecular structures of 1 , 2 , [( 4 )2], 6 , and [( 7 )2] have been determined by X‐ray diffraction. These highlight Ae???H? Si internal β‐agostic interactions, which play a key role in the stabilization of [{LOi}Ae? N(SiMe2H)2] complexes against ligand redistribution reactions, in contrast to regular [{LOi}Ae? N(SiMe3)2]. Pulse‐gradient spin‐echo (PGSE) NMR measurements showed that 1 , 4 , 6 , and 7 are monomeric in solution. Complexes 1 – 7 mediate the ring‐opening polymerization (ROP) of L ‐lactide highly efficiently, converting up to 5000 equivalents of monomer at 25 °C in a controlled fashion. In the immortal ROP performed with up to 100 equivalents of exogenous 9‐anthracenylmethanol or benzyl or propargyl alcohols as a transfer agent, the activity of the catalyst increased with the size of the metal ( 1 < 2 < 3 ). For Ca‐based complexes, the enhanced electron‐donating ability of the ancillary ligand favored catalyst activity ( 1 > 6 > 4 ≈ 5 ). The nature of the alcohol had little effect over the activity of the binary catalyst system 1 /ROH; in all cases, both the control and end‐group fidelity were excellent. In the living ROP of L ‐LA, the HC?CCH2O? initiating group (as in 7 ) proved superior to N(SiMe2H)2? or N(SiMe3)2? (as in 6 or [{LO4}Ca? N(SiMe3)2] ( B ), respectively). 相似文献
107.
108.
The reactions between several derivatives of 1-(3,5-dimethoxyphenyl)-prop-2-yn-1-ol and different ruthenium starting materials [i.e., RuCl?(PPh?)? and RuCl?(p-cymene)(L), where L is tricyclohexylphosphine di-t-butylmethylphosphine, dicyclohexylphenylphosphine, triisobutylphosphine, triisopropylphosphine, or tri-n-propylphosphine] are described. Several of these reactions allow for the easy, in-situ and atom-economic preparation of olefin metathesis catalysts. Organic precursor 1-(3,5-dimethoxyphenyl)-1-phenyl-prop-2-yn-1-ol led to the formation of active ruthenium indenylidene-ether complexes, while 1-(3,5-dimethoxyphenyl)-prop-2-yn-1-ol and 1-(3,5-dimethoxyphenyl)-1-methyl-prop-2-yn-1-ol did not. It was also found that a bulky and strong σ-donor phosphine ligand was required to impart good catalytic activity to the new ruthenium complexes. 相似文献
109.
Yann Ratieuville Philippe Viers Jean Alexandre Grard Durand 《Electrochemistry communications》2000,2(12):2727
As the resonance frequency of an oscillating quartz changes upon the deposition of a given mass to the crystal surface, it can be used as a very sensitive mass measuring device. Despite a growing interest in the use of electrochemical quartz crystal microbalance (EQCM), there is still no commercial available measurement cell which can satisfy all the conditions needed in electrochemical investigations. The design and characteristics of a new electrochemical cell adapted to EQCM measurements are presented. The sensitivity of the microbalance, which is determined by several calibration runs of silver electrodeposition is (183.2±2.9) Hz μg−1 cm2. This value, which is close to the theoretical one, confirms the validity of the system we have developed. The calibration procedure and the EQCM using range are then discussed. 相似文献
110.
Max O. D. G. Baker Nirukshan Shanmugam Chi L. L. Pham Sarah R. Ball Emma Sierecki Yann Gambin Megan Steain Margaret Sunde 《Molecules (Basel, Switzerland)》2022,27(11)
TIR-domain-containing adapter-inducing interferon-β (TRIF) is an innate immune protein that serves as an adaptor for multiple cellular signalling outcomes in the context of infection. TRIF is activated via ligation of Toll-like receptors 3 and 4. One outcome of TRIF-directed signalling is the activation of the programmed cell death pathway necroptosis, which is governed by interactions between proteins that contain a RIP Homotypic Interaction Motif (RHIM). TRIF contains a RHIM sequence and can interact with receptor interacting protein kinases 1 (RIPK1) and 3 (RIPK3) to initiate necroptosis. Here, we demonstrate that the RHIM of TRIF is amyloidogenic and supports the formation of homomeric TRIF-containing fibrils. We show that the core tetrad sequence within the RHIM governs the supramolecular organisation of TRIF amyloid assemblies, although the stable amyloid core of TRIF amyloid fibrils comprises a much larger region than the conserved RHIM only. We provide evidence that RHIMs of TRIF, RIPK1 and RIPK3 interact directly to form heteromeric structures and that these TRIF-containing hetero-assemblies display altered and emergent properties that likely underlie necroptosis signalling in response to Toll-like receptor activation. 相似文献