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排序方式: 共有133条查询结果,搜索用时 31 毫秒
71.
Teresa Küblbck Gaspard Ang Greta Bikelyt Jiina Pokorn Radovan Skcel Thomas M. Klaptke 《Angewandte Chemie (International ed. in English)》2020,59(30):12326-12330
A progressive halogen‐free multicolored smoke system to obtain white, red, violet, yellow, green, and blue smoke color is presented. The nitrogen‐rich salt guanidinium 5,5′‐azotetrazolate (GZT), which is usually applied as a gas generator or propellant ingredient, was combined with different smoke dyes (Solvent Red 1, Solvent Violet 47, Solvent Green 3, Solvent Yellow 33). These two‐component smoke mixtures offer a convenient and safe multicolor approach without the need for potassium chlorate or any other hazardous material. The common smoke characteristics with respect to burn time/burn rate, yield factor, transfer rate, as well as energetic properties were determined and compared with classic chlorate‐based formulations currently used. To the best of our knowledge, nothing comparable is known in the literature and a completely new research area in modern pyrotechnics is opened. 相似文献
72.
Yyves Verbandt Bart Verwilghen Peter Cloetens Luk Van Kempen Hugo Thienpont Irina Veretennicoff Greta Van Vinckenroy W. Patrick De Wilde Marc R. H. Voet 《Optical Review》1997,4(1):A75-A79
An analytical model for the pressure and strain sensitivity of highly-birefringent fibers is proposed which is in excellent agreement with numerical calculations. Results of polarimetry and coherence-multiplexing experiments are presented and a novel method for accurately splicing this kind of fibers is demonstrated. 相似文献
73.
Five novel lanthanoid-containing silicotungstates with polymeric crystal structures [Ln(2)(H(2)O)(7)Si(2)W(18)O(66)](n)(10n-) [Ln = Gd(III) (Gd-1 and Gd-2), Tb(III), Ho(III)] and [Dy(2)(H(2)O)(6.5)(C(2)H(4)O(2))(0.5)Si(2)W(18)O(66)](n)(10n-) were obtained from the one-step reaction of Na(10)[SiW(9)O(34)]·nH(2)O with Ln(NO(3))(3)·nH(2)O in a sodium acetate buffer. The compounds were characterized by single-crystal X-ray diffraction and a wide range of analytical methods, including FT-IR, UV/vis, and photoluminescence spectroscopy as well as electrochemistry and thermogravimetric analysis. This new polyoxotungstate series is the first example of lanthanoids embedded in the open Wells-Dawson silicotungstate anion [α-Si(2)W(18)O(66)](16-). The lanthanoid-containing Wells-Dawson-type polyoxoanions [Ln(2)(H(2)O)(7)Si(2)W(18)O(66)](10-) [Ln = Gd(III) (Gd-1 and Gd-2), Tb(III), Ho(III)] and [Dy(2)(H(2)O)(6.5)(C(2)H(4)O(2))(0.5)Si(2)W(18)O(66)](10-) are linked by Ln(3+) cations to form 3D architectures for Gd-1 or 2D frameworks for the isostructural compounds Tb-2, Dy-2, Ho-2, and Gd-2. The structure-directing influence of the lanthanoid cation on the local structure of the dimeric building blocks and on the crystal packing motifs is investigated in detail. The photoluminescence properties of Tb-2 and Dy-2 were investigated at room temperature, and Ho-2 exhibits an interesting photochromic behavior. The magnetic susceptibility of Gd-1 and Gd-2 was studied in the temperature range between 2 and 300 K for its effective magnetic moment. 相似文献
74.
Forrest WP Cao Z Chen WZ Hassell KM Kharlamova A Jakstonyte G Ren T 《Inorganic chemistry》2011,50(19):9345-9353
A series of dendronized-Ru(2) compounds were prepared using the Cu(I)-catalyzed 1,3-dipolar cycloaddition (click reaction) between the terminal azides of azidopoly(benzyl ether) dendrons ([D(n)]-N(3), n = 0-3) and Ru(2) units bearing one or two terminal ethynes, Ru(2)(D(3,5-Cl(2)Ph)F)(4-m)(DMBA-4-C(2)H)(m)Cl with m = 1 and 2, and D(3,5-Cl(2)Ph)F and DMBA-4-C(2)H as N,N'-bis(3,5-dichloro-phenyl)formamidinate and N,N'-dimethyl-4-ethynylbenzamidinate, respectively. The resultant Ru(2)(D(3,5-Cl(2)Ph)F)(4-m)(DMBA-D(n))(m)Cl compounds were further functionalized by the axial ligand displacement of Cl by -C(2)Ph to yield new compounds Ru(2)(D(3,5-Cl(2)Ph)F)(4-m)(DMBA-D(n))(m)(C(2)Ph)(2) (where m = 1 and 2; n = 0 and 1). All Ru(2) compounds reported herein were analyzed via mass spectrometry, voltammetry, and UV-visible and fluorescence spectroscopy. Density-functional theory (DFT) calculations were performed on a model compound to gain more insight into the molecular orbital energy levels possibly associated with the photophysical data obtained and presented herein. 相似文献
75.
76.
The preparative flexibility of hydrothermal syntheses needs to be systemised for exploring complex structure-synthesis relationships and morphology control options in materials chemistry. This is demonstrated for the targeted hydrothermal preparation of molybdenum oxide materials: firstly, in situ studies were employed for the efficient production of MoO(3) nanofibres. Furthermore, ionic substances as structure-directing tools brought forward a new class of fluorinated polyoxomolybdates. 相似文献
77.
Bernardi L Bonini BF Dessole G Fochi M Comes-Franchini M Gavioli S Ricci A Varchi G 《The Journal of organic chemistry》2003,68(4):1418-1425
A new protocol is described for the stereocontrolled synthesis of pseudo-C(2)-symmetric core units of interest as candidates for HIV protease inhibition. Addition of unbranched and branched organolithium reagents to cyanohydrins from l-phenylalaninal and l-isoleucinal, followed by in situ reduction of the intermediate imines and CHT deprotection under MW irradiation, led to 1,3-diamino alcohols 6a and 8a as the major products in satisfactory to good yields. The first preparation of a previously unreported pseudo-C(2)-symmetric triamino derivative was accomplished expeditiously via high-yielding nitro-Mannich addition of the silylnitronate, from 2-phenyl-1-nitroethane, to the PMP imine derived from l-phenylalaninal. Reduction of the nitro group in the moderately unstable nitro diamine adduct, followed by chromatographic separation of the required diastereoisomer and CHT debenzylation under MW irradiation, led to the 2-PMP-protected triamine 19 isolated as a bis(sulfonamide). 相似文献
78.
Greta Vastakaite Dr. Claudio E. Grünenfelder Prof. Helma Wennemers 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(18):e202200215
Catalytic stereoselective additions with maleimides are useful one-step reactions to yield chiral succinimides, molecules that are widespread among therapeutically active compounds but challenging to prepare when the maleimide is C-substituted. We present the tripeptide H-Pro-Pro-Asp-NHC12H25 as a catalyst for conjugate addition reactions between aldehydes and C-substituted maleimides to form succinimides with three contiguous stereogenic centers in high yields and stereoselectivities. The peptidic catalyst is so chemoselective that no protecting group is needed at the imide nitrogen of the maleimides. Derivatization of the succinimides was straightforward and provided access to chiral pyrrolidines, lactones, and lactams. Kinetic studies, including a Hammett plot, provided detailed insight into the reaction mechanism. 相似文献
79.
Alessandra Garau Giacomo Picci Massimiliano Arca Alexander J. Blake Claudia Caltagirone Greta De Filippo Francesco Demartin Francesco Isaia Vito Lippolis Anna Pintus M. Andrea Scorciapino M. Carla Aragoni 《Molecules (Basel, Switzerland)》2021,26(5)
This study investigates the coordination chemistry of the tetradentate pyridine-containing 12-membered macrocycles L1-L3 towards Platinum Group metal ions PdII, PtII, and RhIII. The reactions between the chloride salts of these metal ions and the three ligands in MeCN/H2O or MeOH/H2O (1:1 v/v) are shown, and the isolated solid compounds are characterized, where possible, by mass spectroscopy and 1H- and 13C-NMR spectroscopic measurements. Structural characterization of the 1:1 metal-to-ligand complexes [Pd(L1)Cl]2[Pd2Cl6], [Pt(L1)Cl](BF4), [Rh(L1)Cl2](PF6), and [Rh(L3)Cl2](BF4)·MeCN shows the coordinated macrocyclic ligands adopting a folded conformation, and occupying four coordination sites of a distorted square-based pyramidal and octahedral coordination environment for the PdII/PtII, and RhIII complexes, respectively. The remaining coordination site(s) are occupied by chlorido ligands. The reaction of L3 with PtCl2 in MeCN/H2O gave by serendipity the complex [Pt(L3)(μ-1,3-MeCONH)PtCl(MeCN)](BF4)2·H2O, in which two metal centers are bridged by an amidate ligand at a Pt1-Pt2 distance of 2.5798(3) Å and feature one square-planar and one octahedral coordination environment. Density Functional Theory (DFT) calculations, which utilize the broken symmetry approach (DFT-BS), indicate a singlet d8-d8 PtII-PtII ground-state nature for this compound, rather than the alleged d9-d7 PtI-PtIII mixed-valence character reported for related dinuclear Pt-complexes. 相似文献
80.
Zero-phonon linewidth and phonon satellites in the optical absorption of nanowire-based quantum dots
The optical properties of quantum dots embedded in a catalytically grown semiconductor nanowire are studied theoretically. In comparison to dots in a bulk environment, the excitonic absorption is strongly modified by the one-dimensional character of the nanowire phonon spectrum. In addition to pronounced satellite peaks due to phonon-assisted absorption, we find a finite width of the zero-phonon line already in the lowest-order calculation. 相似文献