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111.
High-power all-normal-dispersion femtosecond pulse generation from a Yb-doped large-mode-area microstructure fiber laser 总被引:3,自引:0,他引:3
We report on an all-normal-dispersion mode-locked fiber laser based on a large-mode-area Yb-doped microstructure fiber and using a high nonlinear modulation depth semiconductor saturable absorber mirror. The laser delivers 3.3 W of average output power with positively chirped 5.5 ps pulses at a center wavelength of 1033 nm. The pulse repetition rate is 46.4 MHz, which results in an energy per pulse of 71 nJ. These pulses are extracavity dechirped down to 516 fs by using bulk gratings. The average power of the dechirped pulses is 2.3 W, which corresponds to a peak power of more than 96 kW. 相似文献
112.
113.
Maximilian Joost Dr. Pauline Gualco Dr. Yannick Coppel Dr. Karinne Miqueu Dr. Christos E. Kefalidis Dr. Laurent Maron Dr. Abderrahmane Amgoune Dr. Didier Bourissou 《Angewandte Chemie (International ed. in English)》2014,53(3):747-751
Oxidative addition plays a major role in transition‐metal catalysis, but this elementary step remains very elusive in gold chemistry. It is now revealed that in the presence of GaCl3, phosphine gold chlorides promote the oxidative addition of disilanes at low temperature. The ensuing bis(silyl) gold(III) complexes were characterized by quantitative 31P and 29Si NMR spectroscopy. Their structures (distorted Y shape) and the reaction profile of σ(Si? Si) bond activation were analyzed by DFT calculations. These results provide evidence for the intermolecular oxidative addition of σ(Si? Si) bonds to gold and open promising perspectives for the development of new gold‐catalyzed redox transformations. 相似文献
114.
Dr. Alexander Sachse Caroline Wuttke Dr. Elízio Lissner Dr. Michèle Oberson de Souza 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(46):14996-14999
Hierarchically porous ZSM‐5 was achieved by using a simple bottom‐up strategy combining zeolite seeds with imidazolium‐based ionic liquids. The bimodal ZSM‐5 with hexagonal arranged mesopores (3 nm) shows important activity in the acid catalysis of bulky compounds relative to conventional ZSM‐5. 相似文献
115.
“Click” Chemistry Mildly Stabilizes Bifunctional Gold Nanoparticles for Sensing and Catalysis
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Na Li Dr. Pengxiang Zhao Dr. Na Liu María Echeverria Dr. Sergio Moya Dr. Lionel Salmon Dr. Jaime Ruiz Prof. Dr. Didier Astruc 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(27):8363-8369
A large family of bifunctional 1,2,3‐triazole derivatives that contain both a polyethylene glycol (PEG) chain and another functional fragment (e.g., a polymer, dendron, alcohol, carboxylic acid, allyl, fluorescence dye, redox‐robust metal complex, or a β‐cyclodextrin unit) has been synthesized by facile “click” chemistry and mildly coordinated to nanogold particles, thus providing stable water‐soluble gold nanoparticles (AuNPs) in the size range 3.0–11.2 nm with various properties and applications. In particular, the sensing properties of these AuNPs are illustrated through the detection of an analogue of a warfare agent (i.e., sulfur mustard) by means of a fluorescence “turn‐on” assay, and the catalytic activity of the smallest triazole–AuNPs (core of 3.0 nm) is excellent for the reduction of 4‐nitrophenol in water. 相似文献
116.
1,10‐Phenanthroline and Non‐Symmetrical 1,3,5‐Triazine Dipicolinamide‐Based Ligands For Group Actinide Extraction
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Dr. Julia Bisson Dr. Jérémy Dehaudt Dr. Marie‐Christine Charbonnel Dr. Denis Guillaneux Dr. Manuel Miguirditchian Dr. Cécile Marie Nathalie Boubals Guy Dutech Dr. Muriel Pipelier Dr. Virginie Blot Prof. Didier Dubreuil 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(25):7819-7829
The synthesis and evaluation of new extractants for spent nuclear fuel reprocessing are described. New bitopic ligands constituted of phenanthroline and 1,3,5‐triazine cores functionalized by picolinamide groups were designed. Synthetic routes were investigated and optimized to obtain twelve new polyaza‐heterocyclic ligands. In particular, an efficient and versatile methodology was developed to access non‐symmetric 2‐substituted‐4,6‐di(6‐picolin‐2‐yl)‐1,3,5‐triazines from the 1,3,5‐triazapentadiene precursor in the presence of anhydride reagents. Extraction studies showed the ability of both ligand series to extract and separate actinides selectively at different oxidation states (UVI, NpV,VI, AmIII, CmIII, and PuIV) from an acidic solution (3 M HNO3). Phenanthroline‐based ligands show the most promising efficiency for use in the group actinide extraction (GANEX) process due to a higher number of donor nitrogen atoms and a suitable pre‐organization of the dipicolinamide‐1,10‐phenanthroline architecture. 相似文献
117.
Dr. Dorian Didier Dr. Pierre‐Olivier Delaye Marwan Simaan Biana Island Dr. Guillaume Eppe Dr. Hendrik Eijsberg Amir Kleiner Prof. Dr. Paul Knochel Prof. Dr. Ilan Marek 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(4):1038-1048
The copper‐catalyzed carbomagnesiation reaction of cyclopropenyl esters 1 leads to various substituted cyclopropanes species 3 in good yields with very high diastereoselectivities. The reaction proceeds through a syn‐chelated carbomagnesiation reaction and could be extended to various cyclopropenylmethyl ester derivatives 5 . The potential of this approach was illustrated by the preparation of two consecutive all‐carbon quaternary stereocenters. However, the carbometalation reaction needs to be performed at temperature ranging from ?35 to ?20 °C to avoid subsequent fragmentation reaction into stereodefined β,γ‐nonconjugated unsaturated esters 4 . Alternatively, the carbocupration reaction with organocopper species could also be performed to leads to configurationally stable cyclopropyl copper species 2[Cu] . Additionally, when the Lewis acid character of the copper center is decreased (i.e., RCuCNLi), the reaction proceed with an anti‐selectivity. The diastereodivergent behavior of these organometallic species is of synthetic interest, since both diastereomers syn‐ 3 and anti‐ 3 can be obtained, at will, from the same precursor cyclopropenyl esters 1 . 相似文献
118.
Uncatalyzed Hydroamination of Electrophilic Organometallic Alkynes: Fundamental,Theoretical, and Applied Aspects
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Dr. Yanlan Wang Camille Latouche Dr. Amalia Rapakousiou Colin Lopez Prof Isabelle Ledoux‐Rak Dr. Jaime Ruiz Prof. Jean‐Yves Saillard Prof. Didier Astruc 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(26):8076-8088
Simple reactions of the most used functional groups allowing two molecular fragments to link under mild, sustainable conditions are among the crucial tools of molecular chemistry with multiple applications in materials science, nanomedicine, and organic synthesis as already exemplified by peptide synthesis and “click” chemistry. We are concerned with redox organometallic compounds that can potentially be used as biosensors and redox catalysts and report an uncatalyzed reaction between primary and secondary amines with organometallic electrophilic alkynes that is free of side products and fully “green”. A strategy is first proposed to synthesize alkynyl organometallic precursors upon addition of electrophilic aromatic ligands of cationic complexes followed by endo hydride abstraction. Electrophilic alkynylated cyclopentadienyl or arene ligands of Fe, Ru, and Co complexes subsequently react with amines to yield trans‐enamines that are conjugated with the organometallic group. The difference in reactivities of the various complexes is rationalized from the two‐step reaction mechanism that was elucidated through DFT calculations. Applications are illustrated by the facile reaction of ethynylcobalticenium hexafluorophosphate with aminated silica nanoparticles. Spectroscopic, nonlinear‐optical and electrochemical data, as well as DFT and TDDFT calculations, indicate a strong push–pull conjugation in these cobalticenium– and Fe– and Ru–arene–enamine complexes due to planarity or near‐planarity between the organometallic and trans‐enamine groups involving fulvalene iminium and cyclohexadienylidene iminium mesomeric forms. 相似文献
119.
On the Synthesis,Characterization and Reactivity of N‐Heteroaryl–Boryl Radicals,a New Radical Class Based on Five‐Membered Ring Ligands
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Dr. Mohamad‐Ali Tehfe Dr. Stéphane Schweizer Dr. Anne‐Caroline Chany Dr. Cédric Ysacco Dr. Jean‐Louis Clément Dr. Didier Gigmes Dr. Fabrice Morlet‐Savary Prof. Jean‐Pierre Fouassier Dr. Markus Neuburger Dr. Théophile Tschamber Dr. Nicolas Blanchard Prof. Jacques Lalevée 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(17):5054-5063
The synthesis and physical characterization of a new class of N‐heterocycle–boryl radicals is presented, based on five membered ring ligands with a N(sp2) complexation site. These pyrazole–boranes and pyrazaboles exhibit a low bond dissociation energy (BDE; B?H) and accordingly excellent hydrogen transfer properties. Most importantly, a high modulation of the BDE(B?H) by the fine tuning of the N‐heterocyclic ligand was obtained in this series and could be correlated with the spin density on the boron atom of the corresponding radical. The reactivity of the latter for small molecule chemistry has been studied through the determination of several reaction rate constants corresponding to addition to alkenes and alkynes, addition to O2, oxidation by iodonium salts and halogen abstraction from alkyl halides. Two selected applications of N‐heterocycle–boryl radicals are also proposed herein, for radical polymerization and for radical dehalogenation reactions. 相似文献
120.
Organ Repair,Hemostasis, and In Vivo Bonding of Medical Devices by Aqueous Solutions of Nanoparticles
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Prof. Dr. Anne Meddahi‐Pellé Aurélie Legrand Dr. Alba Marcellan Liliane Louedec Prof. Dr. Didier Letourneur Prof. Dr. Ludwik Leibler 《Angewandte Chemie (International ed. in English)》2014,53(25):6369-6373
Sutures are traumatic to soft connective tissues, such as liver or lungs. Polymer tissue adhesives require complex in vivo control of polymerization or cross‐linking reactions and currently suffer from being toxic, weak, or inefficient within the wet conditions of the body. Herein, we demonstrate using Stöber silica or iron oxide nanoparticles that nanobridging, that is, adhesion by aqueous nanoparticle solutions, can be used in vivo in rats to achieve rapid and strong closure and healing of deep wounds in skin and liver. Nanoparticles were also used to fix polymer membranes to tissues even in the presence of blood flow, such as occurring after liver resection, yielding permanent hemostasis within a minute. Furthermore, medical devices and tissue engineering constructs were fixed to organs such as a beating heart. The simplicity, rapidity, and robustness of nanobridging bode well for clinical applications, surgery, and regenerative medicine. 相似文献