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511.
Myriam Roy Veronika Berezhnaia Marco Villa Nicolas Vanthuyne Michel Giorgi Jean‐Valre Naubron Salom Poyer Valrie Monnier Laurence Charles Yannick Carissan Denis Hagebaum‐Reignier Jean Rodriguez Marc Gingras Yoann Coquerel 《Angewandte Chemie (International ed. in English)》2020,59(8):3264-3271
We report a molecular design and concept using π‐system elongation and steric effects from helicenes surrounding a triphenylene core toward stable chiral polycyclic aromatic hydrocarbons (PAHs) with a maximal π‐distortion to tackle their aromaticity, supramolecular and molecular properties. The selective syntheses, and the structural, conformational and chiroptical properties of two diastereomeric large multi‐helicenes of formula C90H48 having a triphenylene core and embedding three [5]helicene units on their inner edges and three [7]helicene units at their periphery are reported based on diastereoselective and, when applicable, enantiospecific Yamamoto‐type cyclotrimerizations of racemic or enantiopure 9,10‐dibromo[7]helicene. Both molecules have an extremely distorted triphenylene core, and one of them exhibits the largest torsion angle recorded so far for a benzene ring (twist=36.9°). 相似文献
512.
Dr. Marcel Leroux Wan-Yun Huang Yannick Lemke Thaddäus J. Koller Prof. Dr. Konstantin Karaghiosoff Prof. Dr. Paul Knochel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(41):8951-8957
Chiral β-aminoalkylzinc halides were prepared starting from optically pure commercial β-amino-alcohols. These amino-alcohols were converted to the corresponding N-pyrrolyl-protected alkyl iodides which undergo a zinc insertion in the presence of LiCl (THF, 25 °C, 10–90 min). Subsequent Negishi cross-coupling or acylation reactions with acid chlorides produced amino-derivatives with retention of chirality. Diastereoselective CBS-reductions of some prepared N-pyrrolyl-ketones provided 1,3-subsituted N-pyrrolyl-alcohols with high diastereoselectivity. Additionally, a deprotection procedure involving an ozonolysis allowed the conversion of the pyrrole-ring into a formamide without loss of optical purity. 相似文献
513.
Jrme Long Ivan V. Basalov Konstantin A. Lyssenko Anton V. Cherkasov Ekaterina Mamontova Yannick Guari Joulia Larionova Alexander A. Trifonov 《化学:亚洲杂志》2020,15(17):2706-2715
We report here the synthesis, structure, magnetic and photoluminescent properties of three new bifunctional Schiff‐base complexes [Dy(L1)2(py)2][B(Ph)4]?py ( 1 ), [Dy(L1)2Cl(DME)] ? 0.5DME ( 2 ) and [Dy(L2)2Cl] ? 2.5(C7H8) ( 3 ) (HL1=Phenol, 2,4‐bis(1,1‐dimethylethyl)‐6‐[[(2‐methoxy‐5‐methylphenyl)imino]methyl]; HL2=Phenol, 2,4‐bis(1,1‐dimethylethyl)‐6‐[[(2‐methoxyphenyl)imino]methyl]). The coordination environment of the Dy3+ ion and the direction of the anisotropic axis may be controlled by the combination of the substituent groups of the Schiff bases, the nature of the counter‐ions (Cl? vs. BPh4?) and the coordinative solvent molecules. A zero‐field slow relaxation of the magnetization is evidenced for all complexes but strong differences in the relaxation dynamics are observed depending on the Dy3+ site geometry. In this sense, complex 1 exhibits an anisotropy barrier of 472 cm?1, which may be favourably compared to other related examples due to the shortening of the Dy?O bond in the axial direction. Besides, the three complexes exhibit a ligand‐based luminescence making them as bifunctional magneto‐luminescent systems. 相似文献
514.
515.
Ludovic Rapp Catalin Constantinescu Yannick Larmande Anne Patricia Alloncle Philippe Delaporte 《Applied Physics A: Materials Science & Processing》2014,115(1):333-339
Laser-induced forward transfer (LIFT) has been investigated for the transfer of a polymeric material. This study focuses on the comparison of the printing process using conventional LIFT printing with a simple square mask and an optimized LIFT technique using a double mask setup, i.e. smart beam shaping (SBS). The purpose is to optimize the energy repartition on the donor layer using a beam profile with over-intensities at the edges and low intensities in the center. This allows the incoming irradiation fluence on the donor layer to be kept as low as possible in the central area, thus preventing the organic pixels being damaged by laser irradiation. The influence of the film’s thickness on the SBS efficiency is discussed. 相似文献
516.
Clément Mouhot Emmanuel Russ Yannick Sire 《Journal de Mathématiques Pures et Appliquées》2011,95(1):72-84
We prove a fractional version of Poincaré inequalities in the context of endowed with a fairly general measure. Namely we prove a control of an norm by a non-local quantity, which plays the role of the gradient in the standard Poincaré inequality. The assumption on the measure is the fact that it satisfies the classical Poincaré inequality, so that our result is an improvement of the latter inequality. Moreover we also quantify the tightness at infinity provided by the control on the fractional derivative in terms of a weight growing at infinity. The proof goes through the introduction of the generator of the Ornstein–Uhlenbeck semigroup and some careful estimates of its powers. To our knowledge this is the first proof of fractional Poincaré inequality for measures more general than Lévy measures. 相似文献
517.
Yannick Baraud 《Probability Theory and Related Fields》2011,151(1-2):353-401
We observe a random measure N and aim at estimating its intensity s. This statistical framework allows to deal simultaneously with the problems of estimating a density, the marginals of a multivariate distribution, the mean of a random vector with nonnegative components and the intensity of a Poisson process. Our estimation strategy is based on estimator selection. Given a family of estimators of s based on the observation of N, we propose a selection rule, based on N as well, in view of selecting among these. Little assumption is made on the collection of estimators and their dependency with respect to the observation N need not be known. The procedure offers the possibility to deal with various problems among which model selection, convex aggregation and construction of T-estimators as studied recently in Birgé (Ann Inst H Poincaré Probab Stat 42(3):273?C325, 2006). For illustration, we shall consider the problems of estimation, complete variable selection and selection among linear estimators in possibly non-Gaussian regression settings. 相似文献
518.
Free-radical three-component carboalkynylation and -alkenylation of olefins have been developed. These involve the addition, across the double bond of an unactivated olefin, of a radical species α- to an electron-withdrawing group and an alkenyl or alkynyl moiety, derived from the corresponding sulfones. 相似文献
519.
Vinzenz X Grosse W Linne U Meissner B Essen LO 《Chemical communications (Cambridge, England)》2011,47(39):11071-11073
The suitability for chemical engineering of the highly symmetrical Mycobacterium tuberculosis dodecin was investigated, its inner cavity providing a large compartment shields introduced compounds from bulk solvent. Hybrids were obtained by S-alkylation of cysteine mutants and characterized by spectroscopic methods, including the crystal structures of wild type and biohybrid dodecins. 相似文献
520.
For the modeling of micro-heterogeneous materials, models are required that take into account the microstructure. More and more, computational homogenization is used to quantify the effective macroscopic response. The large number of resulting microscopic boundary value problems need to be solved efficiently. To reduce the computational effort and simulation time, model reduction methods may be applied. In this contribution the performance of the proper orthogonal decomposition is analyzed for the wave propagation in fiber reinforced materials. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献