共查询到20条相似文献,搜索用时 15 毫秒
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Dr. Peter J. Byrne Dr. Patricia J. Richardson Dr. John Chang Dr. Anna F. Kusmartseva Dr. David R. Allan Dr. Anita C. Jones Dr. Konstantin V. Kamenev Prof. Peter A. Tasker Prof. Simon Parsons 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(25):7738-7748
The crystal structures of bis(3‐fluoro‐salicylaldoximato)nickel(II) and bis(3‐methoxy‐salicylaldoximato)nickel(II) have been determined at room temperature between ambient pressure and approximately 6 GPa. The principal effect of pressure is to reduce intermolecular contact distances. In the fluoro system molecules are stacked, and the Ni???Ni distance decreases from 3.19 Å at ambient pressure to 2.82 Å at 5.4 GPa. These data are similar to those observed in bis(dimethylglyoximato)nickel(II) over a similar pressure range, though contrary to that system, and in spite of their structural similarity, the salicyloximato does not become conducting at high pressure. Ni–ligand distances also shorten, on average by 0.017 and 0.011 Å for the fluoro and methoxy complexes, respectively. Bond compression is small if the bond in question is directed towards an interstitial void. A band at 620 nm, which occurs in the visible spectrum of each derivative, can be assigned to a transition to an antibonding molecular orbital based on the metal 3d(x2?y2) orbital. Time‐dependent density functional theory calculations show that the energy of this orbital is sensitive to pressure, increasing in energy as the Ni–ligand distances are compressed, and consequently increasing the energy of the transition. The resulting blueshift of the UV‐visible band leads to piezochromism, and crystals of both complexes, which are green at ambient pressure, become red at 5 GPa. 相似文献
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Shuai Wang Dr. Jose A. Cuesta‐Seijo Dr. Dominique Lafont Prof. Monica M. Palcic Dr. Sébastien Vidal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(45):15346-15357
A series of ten glycosyltransferase inhibitors has been designed and synthesized by using pyridine as a pyrophosphate surrogate. The series was prepared by conjugation of carbohydrate, pyridine, and nucleoside building blocks by using a combination of glycosylation, the Staudinger–Vilarrasa amide‐bond formation, and azide–alkyne click chemistry. The compounds were evaluated as inhibitors of five metal‐dependent galactosyltransferases. Crystallographic analyses of three inhibitors complexed in the active site of one of the enzymes confirmed that the pyridine moiety chelates the Mn2+ ion causing a slight displacement (2 Å) from its original position. The carbohydrate head group occupies a different position than in the natural uridine diphosphate (UDP)–Gal substrate with little interaction with the enzyme. 相似文献
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Donghoon Seoung Yongmoon Lee Dr. Chi‐Chang Kao Prof. Dr. Thomas Vogt Prof. Dr. Yongjae Lee 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(33):10876-10883
High‐pressure synchrotron X‐ray powder diffraction studies of a series of alkali‐metal‐exchanged natrolites, A16Al16Si24O80 ? n H2O (A=Li, K, Na, Rb, and Cs and n=14, 16, 22, 24, 32), in the presence of water, reveal structural changes that far exceed what can be achieved by varying temperature and chemical composition. The degree of volume expansion caused by pressure‐induced hydration (PIH) is inversely proportional to the non‐framework cation radius. The expansion of the unit‐cell volume through PIH is as large as 20.6 % in Li‐natrolite at 1.0 GPa and decreases to 6.7, 3.8, and 0.3 % in Na‐, K‐, and Rb‐natrolites, respectively. On the other hand, the onset pressure of PIH appears to increase with non‐framework cation radius up to 2.0 GPa in Rb‐natrolite. In Cs‐natrolite, no PIH is observed but a new phase forms at 0.3 GPa with a 4.8 % contracted unit cell and different cation–water configuration in the pores. In K‐natrolite, the elliptical channel undergoes a unique overturn upon the formation of super‐hydrated natrolite K16Al16Si24O80 ? 32 H2O at 1.0 GPa, a species that reverts back above 2.5 GPa as the potassium ions interchange their locations with those of water and migrate from the hinge to the center of the pores. Super‐hydrated zeolites are new materials that offer numerous opportunities to expand and modify known chemical and physical properties by reversibly changing the composition and structure using pressure in the presence of water. 相似文献
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Dr. Jose L. Jordá Prof. Fernando Rey Dr. German Sastre Dr. Susana Valencia Miguel Palomino Prof. Avelino Corma Prof. Alfredo Segura Prof. Daniel Errandonea Dr. Raúl Lacomba Prof. Francisco J. Manjón Dr. Óscar Gomis Dr. Annette K. Kleppe Prof. Andrew P. Jephcoat Dr. Mónica Amboage Dr. J. Alberto Rodríguez‐Velamazán 《Angewandte Chemie (International ed. in English)》2013,52(40):10458-10462
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Lee Y Lee Y Seoung D Im JH Hwang HJ Kim TH Liu D Liu Z Lee SY Kao CC Vogt T 《Angewandte Chemie (International ed. in English)》2012,51(20):4848-4851
High-pressure ion exchange of small-pore zeolite K-natrolite allows immobilization of nominally non-exchangeable aliovalent cations such as trivalent europium. A sample exchanged at 3.0(1) GPa and 250 °C contains about 4.7 Eu(III) ions per unit cell, which is equivalent to over 90 % of the K(+) cations being exchanged. 相似文献
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Stefan J. Sedlmaier Vinicius R. Celinski Dr. Jörn Schmedt auf der Günne Prof. Dr. Wolfgang Schnick 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(14):4358-4366
The first crystalline phosphorus oxonitride imide H3P8O8N9 (=P8O8N6(NH)3) has been synthesized under high‐pressure and high‐temperature conditions. To this end, a new, highly reactive phosphorus oxonitride imide precursor compound was prepared and treated at 12 GPa and 750 °C by using a multianvil assembly. H3P8O8N9 was obtained as a colorless, microcrystalline solid. The crystal structure of H3P8O8N9 was solved ab initio by powder X‐ray diffraction analysis, applying the charge‐flipping algorithm, and refined by the Rietveld method (C2/c (no. 15), a=1352.11(7), b=479.83(3), c=1820.42(9) pm, β=96.955(4)°, Z=4). H3P8O8N9 exhibits a highly condensed (κ=0.47), 3D, but interrupted network that is composed of all‐side vertex‐sharing (Q4) and only threefold‐linking (Q3) P(O,N)4 tetrahedra in a Q4/Q3 ratio of 3:1. The structure, which includes 4‐ring assemblies as the smallest ring size, can be subdivided into alternating open‐branched zweier double layers {oB,${2{{2\hfill \atop \infty \hfill}}}$ }[2P3(O,N)7] and layers containing pairwise‐linked Q3 tetrahedra parallel (001). Information on the hydrogen atoms in H3P8O8N9 was obtained by 1D 1H MAS, 2D homo‐ and heteronuclear (together with 31P) correlation NMR spectroscopy, and a 1H spin‐diffusion experiment with a hard‐pulse sequence designed for selective excitation of a single peak. Two hydrogen sites with a multiplicity ratio of 2:1 were identified and thus the formula of H3P8O8N9 was unambiguously determined. The protons were assigned to Wyckoff positions 8f and 4e, the latter located within the Q3 tetrahedra layers. 相似文献
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Prof. Polly L. Arnold Dr. Alessandro Prescimone Dr. Joy H. Farnaby Dr. Stephen M. Mansell Prof. Simon Parsons Prof. Nikolas Kaltsoyannis 《Angewandte Chemie (International ed. in English)》2015,54(23):6735-6739
The diuranium(III) compound [UN′′2]2(μ‐η6:η6‐C6H6) (N′′=N(SiMe3)2) has been studied using variable, high‐pressure single‐crystal X‐ray crystallography, and density functional theory . In this compound, the low‐coordinate metal cations are coupled through π‐ and δ‐symmetric arene overlap and show close metal? CH contacts with the flexible methyl CH groups of the sterically encumbered amido ligands. The metal–metal separation decreases with increasing pressure, but the most significant structural changes are to the close contacts between ligand CH bonds and the U centers. Although the interatomic distances are suggestive of agostic‐type interactions between the U and ligand peripheral CH groups, QTAIM (quantum theory of atoms‐in‐molecules) computational analysis suggests that there is no such interaction at ambient pressure. However, QTAIM and NBO analyses indicate that the interaction becomes agostic at 3.2 GPa. 相似文献
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Growth of large diamond crystals by reduction of magnesium carbonate with metallic sodium 总被引:2,自引:0,他引:2
Lou Z Chen Q Wang W Qian Y Zhang Y 《Angewandte Chemie (International ed. in English)》2003,42(37):4501-4503
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Dr. Andrey Yu. Manakov Dr. Anna Yu. Likhacheva Dr. Vladimir A. Potemkin Dr. Andrey G. Ogienko Dr. Alexander V. Kurnosov Dr. Aleksei I. Ancharov 《Chemphyschem》2011,12(13):2476-2484
Experimental data on the pressure dependence of unit cell parameters for the gas hydrates of ethane (cubic structure I, pressure range 0–2 GPa), xenon (cubic structure I, pressure range 0–1.5 GPa) and the double hydrate of tetrahydrofuran+xenon (cubic structure II, pressure range 0–3 GPa) are presented. Approximation of the data using the cubic Birch–Murnaghan equation, P=1.5B0[(V0/V)7/3?(V0/V)5/3], gave the following results: for ethane hydrate V0=1781 Å3, B0=11.2 GPa; for xenon hydrate V0=1726 Å3, B0=9.3 GPa; for the double hydrate of tetrahydrofuran+xenon V0=5323 Å3, B0=8.8 GPa. In the last case, the approximation was performed within the pressure range 0–1.5 GPa; it is impossible to describe the results within a broader pressure range using the cubic Birch–Murnaghan equation. At the maximum pressure of the existence of the double hydrate of tetrahydrofuran+xenon (3.1 GPa), the unit cell volume was 86 % of the unit cell volume at zero pressure. Analysis of the experimental data obtained by us and data available from the literature showed that 1) the bulk modulus of gas hydrates with classical polyhedral structures, in most cases, are close to each other and 2) the bulk modulus is mainly determined by the elasticity of the hydrogen‐bonded water framework. Variable filling of the cavities with guest molecules also has a substantial effect on the bulk modulus. On the basis of the obtained results, we concluded that the bulk modulus of gas hydrates with classical polyhedral structures and existing at pressures up to 1.5 GPa was equal to (9±2) GPa. In cases when data on the equations of state for the hydrates were unavailable, the indicated values may be recommended as the most probable ones. 相似文献
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Karau FW Seyfarth L Oeckler O Senker J Landskron K Schnick W 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(24):6841-6852
SrP2N4 was obtained by high-pressure high-temperature synthesis utilizing the multianvil technique (5 GPa, 1400 degrees C) starting from mixtures of phosphorus(V) nitride and strontium azide. SrP2N4 turned out to be isotypic with BaGa(2)O(4) and is closely related to KGeAlO(4). The crystal structure (SrP2N4, a=17.1029(8), c=8.10318(5) A, space group P6(3) (no. 173), V=2052.70(2) A3, Z=24, R(F2)=0.0633) was solved from synchrotron powder diffraction data by applying a combination of direct methods, Patterson syntheses, and difference Fourier maps adding the unit cell information derived from electron diffraction and symmetry information obtained from 31P solid-state NMR spectroscopy. The structure of SrP2N4 was refined by the Rietveld method by utilizing both neutron and synchrotron X-ray powder diffraction data, and has been corroborated additionally by 31P solid-state NMR spectroscopy by employing through-bond connectivities and distance relations. 相似文献
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Synthesis and crystal structures of two new compounds, K2[CrCl5(H2O)] ( I ) and (NH4)2[CrCl5(H2O)] ( II ) are reported. Both compounds were prepared from chromium(VI) salts by two different methods and reaction pathways of these syntheses are suggested. The crystal structures of these two aquapentachlorochromates(III) have been determined from three dimensional X‐ray data collected at low temperature, 173 K. The two structures are isomorphous and their unit cell dimensions are quite similar. They are orthorhombic, space groups Pnma, with Z = 4. Both structures are composed of [CrCl5(H2O)]2? units held together by the counterion framework. The coordination around the chromium ion deviates from a regular octahedron due to the shorter equatorial chromium‐oxygen bond. 相似文献
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K Oka T Koyama T Ozaaki S Mori Y Shimakawa M Azuma 《Angewandte Chemie (International ed. in English)》2012,51(32):7977-7980
The monoclinic perovskite BiCo(1-x) Fe(x) O(3) (x≈0.7) undergoes a second-order structural transition from tetragonal to monoclinic, which is accompanied by a rotation of the polarization vector from the [001] to [111] directions of a pseudo cubic cell. The crystal structure, determined by electron diffraction and powder synchrotron X-ray diffraction, was the same as that of Pb(Ti(1-x) Zr(x) )O(3) at the morphotropic phase boundary. 相似文献