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21.
Raman Spectra of the Iodine (III) Nitrates CF3I(NO3)2, C6H5I(NO3)2, and I(NO3)3 The Raman spectra of the title compounds are recorded and discussed. 相似文献
22.
Template Reaction of Bis(acetylacetonato)-dioxo-molybdenum(VI) with Benzoylhydrazone By reaction of bis(acetylacetonato)-dioxo-molybdenum(VI) with benzoylhydrazine benzoylhydrazido(2?)-acetylacetonebenzoylhydrazonato(2?)-oxo-molybdenum(VI) was formed beside another species. The compound was characterized by mass spectrometry and X-ray structural analysis. Crystallographic data see ?Inhaltsübersicht”?. 相似文献
23.
First Magnetoplumbite Structure Including Rare Earth Ions: Nd2Fe Fe Al9O38 The hitherto unknown compound Nd2Fe15Al9O38 with magnetoplumbite structure was prepared. The symmetry of the isolated red-brown single crystals was determined by X-ray single crystal work (space group D? P63//mmc; a = 568.7; c = 2 223 pm; Z = 2) and the distribution of Fe and Al to the metal positions was identified. 相似文献
24.
Christian Lehmann Bernd Schweizer Christian Leumann Albert Eschenmoser 《Helvetica chimica acta》1997,80(5):1421-1442
Chemistry of α-Aminonitriles. Regioselective Synthesis and Crystal Structure of Uroporphyrinogen (Type I) Octanitrile A regioselective synthesis of uroporphyrinogen-octanitrile (type I) based on the strategy of multiple use of (dimethylmethylidene)ammonium iodide for stepwise regioselective functionalization of the pyrrole nucleus is described. This uroporphyrinogen derivative is remarkably stable and beautifully crystallizes in space group P1 with one molecule per unit cell. The crystal structure of the compound shows interesting conformational characteristics which are interpreted to be caused by subtle stereoelectronic effects. The English Footnotes to Schemes 1-3 and Figs. 1-12 provide an extension of this summary. 相似文献
25.
Furstner A Liebl M Lehmann CW Picquet M Kunz R Bruneau C Touchard D Dixneuf PH 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(10):1847-1857
A series of well accessible cationic ruthenium allenylidene complexes of the general type [(eta6-arene)(R3P)RuCl(=C=CR'2)]+ X- is described which constitute a new class of pre-catalysts for ring closing olefin metathesis reactions (RCM) and provide an unprecedented example for the involvement of metal allenylidenes in catalysis. They effect the cyclization of various functionalized dienes and enynes with good to excellent yields and show a great tolerance towards an array of functional groups. Systematic variations of their basic structural motif have provided insights into the essential parameters responsible for catalytic activity which can be enhanced further by addition of Lewis or Bronsted acids, by irradiation with UV light, or by the adequate choice of the "non-coordinating" counterion X-. The latter turned out to play a particularly important role in determining the rate and selectivity of the reaction. A similarly pronounced influence is exerted by remote substituents on the allenylidene residue which indicates that this ligand (or a ligand derived thereof) may remain attached to the metal throughout the catalytic process. X-ray crystal structures of the catalytically active allenylidene complexes 3b.PF6 and 15.OTf as well as of the chelate complex 10 required for the preparation of the latter catalyst are reported. 相似文献
26.
Lehmann JF Schrobilgen GJ Christe KO Kornath A Suontamo RJ 《Inorganic chemistry》2004,43(22):6905-6921
The single-crystal X-ray structures of [XF(6)][Sb(2)F(11)] (X = Cl, Br, I) have been determined and represent the first detailed crystallographic study of salts containing the XF(6)(+) cations. The three salts are isomorphous and crystallize in the monoclinic space group P2(1)/n with Z = 4: [ClF(6)][Sb(2)F(11)], a = 11.824(2) A, b = 8.434(2) A, c = 12.088(2) A, beta = 97.783(6) degrees , V = 1194.3(4) A(3), R(1) = 0.0488 at -130 degrees C; [BrF(6)][Sb(2)F(11)], a = 11.931(2) A, b = 8.492(2) A, c = 12.103(2) A, beta = 97.558(4) degrees , V = 1215.5(4) A(3), R(1) = 0.0707 at -130 degrees C; [IF(6)][Sb(2)F(11)], a = 11.844(1) A, b = 8.617(1) A, c = 11.979(2) A, beta = 98.915(2) degrees , V = 1207.8(3) A(3), R(1) = 0.0219 at -173 degrees C. The crystal structure of [IF(6)][Sb(2)F(11)] was also determined at -100 degrees C and was found to crystallize in the monoclinic space group P2(1)/m with Z = 4, a = 11.885(1) A, b = 8.626(1) A, c = 12.000(1) A, beta = 98.44(1), V = 1216.9(2) A(3), R(1) = 0.0635. The XF(6)(+) cations have octahedral geometries with average Cl-F, Br-F, and I-F bond lengths of 1.550(4), 1.666(11) and 1.779(6) [-173 degrees C]/1.774(8) [-100 degrees C] A, respectively. The chemical shifts of the central quadrupolar nuclei, (35,37)Cl, (79,81)Br, and (127)I, were determined for [ClF(6)][AsF(6)] (814 ppm), [BrF(6)][AsF(6)] (2080 ppm), and [IF(6)][Sb(3)F(16)] (3381 ppm) in anhydrous HF solution at 27 degrees C, and spin-inversion-recovery experiments were used to determine the T(1)-relaxation times of (35)Cl (1.32(3) s), (37)Cl (2.58(6) s), (79)Br (24.6(4) ms), (81)Br (35.4(5) ms), and (127)I (6.53(1) ms). Trends among the central halogen chemical shifts and T(1)-relaxation times of XF(6)(+), XO(4)(-), and X(-) are discussed. The isotropic (1)J-coupling constants and reduced coupling constants for the XF(6)(+) cations and isoelectronic hexafluoro species of rows 3-6 are empirically assessed in terms of the relative contributions of the Fermi-contact, spin-dipolar, and spin-orbit mechanisms. Electronic structure calculations using Hartree-Fock, MP2, and local density functional methods were used to determine the energy-minimized gas-phase geometries, atomic charges, and Mayer bond orders of the XF(6)(+) cations. The calculated vibrational frequencies are in accord with the previously published assignments and experimental vibrational frequencies of the XF(6)(+) cations. Bonding trends within the XF(6)(+) cation series have been discussed in terms of natural bond orbital (NBO) analyses, the ligand close-packed (LCP) model, and the electron localization function (ELF). 相似文献
27.
Investigation of potential-sensitive fluorescent dyes for application in nitrate sensitive polymer membranes 总被引:2,自引:0,他引:2
Gerhard J. Mohr Frank Lehmann Ralf Östereich Ivana Murkovic Otto S. Wolfbeis 《Analytical and bioanalytical chemistry》1997,357(3):284-291
The applicability of various potential-sensitive dyes (PSD) for optical sensing of anions is reported. Specifically, nitrate-responsive
polymer membranes have been developed which are composed of a plasticized polymer, an anion exchange catalyst, and a fluorescent
dye. On exposure to nitrate, the fluorescence intensity of such membranes increases, while the wavelengths of the excitation
and emission maxima remain virtually unchanged. The membranes typically are 2–4 μm thick and exhibit highest sensitivity to
nitrate in the 2 to 200 mgl–1 range. Signal changes on exposure to 100 mmol/l nitrate can be as high as +300%. The detection limit is 0.2 mgl–1. The cationic PSD octadecyl acridine organe was tested in combination with a tin-organic and an indium-organic anion carrier
rather than with tridodecylmethylammonium chloride, but both carriers were found to display no improved selectivity.
Received: 2 December 1995 / Revised: 28 March 1996 / Accepted: 5 April 1996 相似文献
28.
CF3I(NO3)2 is formed from the reactions of CF3IF2 or CF3IO with N2O5 as well as CF3I with ClNO3. During the reactions of CF3IF2 with N2O5 or CF3I with ClNO3 the intermediate products CF3IF(NO3) or CF3ICl(NO3) can be identified. The preparations, properties, 19F-nmr spectra and the thermal decomposition of CF3I(NO3)2 are described. 相似文献
29.
Kinetic investigations of thermo-controlled two-step reactions between an uretdione cross-linker and OH-groups are undertaken. Non-isothermal DSC measurements are chosen for the determination of the kinetic parameters (E, A, n) using of THERMOKINETICS software. The system can be described very accurately with a four-step kinetic model of consecutive reactions. On the basis of the kinetic model and parameters the realization of the first reaction step, which is the formation of the allophanate network is simulated. Finally, the result of the calculated progress of the reaction is evaluated by FT-IR and isothermal DSC measurements. 相似文献
30.
Xiangbing Zeng Silvio Poppe Anne Lehmann Marko Prehm Changlong Chen Feng Liu Huanjun Lu Goran Ungar Carsten Tschierske 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(22):7453-7457
The first single‐diamond cubic phase in a liquid crystal is reported. This skeletal structure with the space group is formed by self‐assembly of bolaamphiphiles with swallow‐tailed lateral chains. It consists of bundles of π‐conjugated p‐terphenyl rods fused into an infinite network by hydrogen‐bonded spheres at tetrahedral four‐way junctions. We also present a quantitative model relating molecular architecture to the space‐filling requirements of six possible bicontinuous cubic phases, that is, the single‐ and double‐network versions of gyroid, diamond, and “plumber′s nightmare”. 相似文献