Ein weiteres Silicat-Anion: [Si(NCSe)6]2– / A Further Silicate Anion: [Si(NCSe)6]2–

1988 ◽  
Vol 43 (7) ◽  
pp. 857-861 ◽  
Author(s):  
Wolfgang Heininger ◽  
Kurt Polborn ◽  
Günter Nagorsen
Keyword(s):  
Ir Spectra ◽  
Complex Anion ◽  
Molar Conductance ◽  
Acetonitrile Solution ◽  
Tetragonal Modification ◽  
Silicate Anion ◽  
X Ray ◽  
Low Concentrations ◽  
Orthorhombic Modification ◽  
Partial Dissociation

Abstract Reaction of SiCl4 with NMe4NCSe or NEt4NCSe in cold acetonitrile leads to the corresponding crystalline salts of the new hexa-coordinate silicon complex anion [Si(NCSe)6]2- (1 ] ; . Their crystallographic data were determined: [NMe4]2[Si(NCSe)6]: rhombohedral. R3̄. a = 897 pm. a = 84.1°. Z = 1. [NEt4]2[Si(NCSe)6], tetragonal modification (from pure acetonitrile): P42/m, a = 1056 pm. c - 1580 pm. Z = 2. [NEt4]2[Si(NCSe)6]. orthorhombic modification (from acetonitrile containing NEt4Cl): a = 1704 pm. b = 1986 pm. c = 1028 pm. Z = 4. N-bonding of the NCSe groups in [Si(NCSe)6]2 is proved by the X-ray structure analysis of [NMe4]2[Si(NCSe)6] and by IR spectra. The concentration dependence of the molar conductance of an acetonitrile solution of [NMe4]2[Si(NCSe)6] was studied. At low concentrations partial dissociation of the hexa-isoselenocyanatosilicate ion is observed.

Ein neues Silicat-Anion: [Si(NCS)6]2- / A New Silicate Anion: [Si(NCS)6]2-

1986 ◽  
Vol 41 (6) ◽  
pp. 702-707 ◽  
Author(s):  
Wolfgang Heininger ◽  
Rolf Stucka ◽  
Günter Nagorsen
Keyword(s):  
Ir Spectra ◽  
Structure Analysis ◽  
Complex Anion ◽  
Crystallographic Data ◽  
Silicate Anion ◽  
X Ray ◽  
Bond Lengths ◽  
Stoichiometric Reaction ◽  
The Mean

Crystalline salts of the new hexa-co-ordinated silicon complex anion [Si(NCS)6]2- were obtained by stoichiometric reaction of Si(NCS)4 with NEt4NCS. NMe4NCS or [DABCO · 2 Me](NCS)2 in acetonitrile. Their crystallographic data were determined: [NEt4]2[Si(NCS)6]: tetragonal, P42/m, a = 1049 pm, c = 1546 pm, Z = 2.[NMe4]2[Si(NCS)6]: rhombohedral, a = 879 pm, α = 83.2°, Z = 1.[DABCO · 2 Me][Si(NCS)6]: triclinic, a = 933 pm, b = 1511 pm, c = 899 pm, α = 105.8°, β = 96.3°, γ = 103.5°, Z = 2.The X-ray structure analysis of [NEt4]2[Si(NCS)6] shows silicon to be coordinated nearly octahedrally by the nitrogen atoms of two linear and four slightly bent NCS groups. The mean Si−N, N−C and C−S bond lengths are 182.1 pm. 115.2 pm and 160.3 pm, respectively.IR spectra are reported. The positions of the [Si(NCS)6]2- bands are discussed in context with the structure.

Microtubule nucleation sequence studied by time-resolved x-ray scattering and electron microscopy

1983 ◽  
Vol 41 ◽  
pp. 766-767
Author(s):  
Eva-Maria Mandelkow ◽  
Eckhard Mandelkow ◽  
Joan Bordas
Keyword(s):  
Electron Microscopy ◽  
Dynamic Equilibrium ◽  
Time Resolved ◽  
X Ray ◽  
Additional Information ◽  
X Ray Scattering ◽  
Low Concentrations ◽  
Microtubule Growth ◽  
Ray Patterns ◽  
Ray Scattering

When a solution of microtubule protein is changed from non-polymerising to polymerising conditions (e.g. by temperature jump or mixing with GTP) there is a series of structural transitions preceding microtubule growth. These have been detected by time-resolved X-ray scattering using synchrotron radiation, and they may be classified into pre-nucleation and nucleation events. X-ray patterns are good indicators for the average behavior of the particles in solution, but they are difficult to interpret unless additional information on their structure is available. We therefore studied the assembly process by electron microscopy under conditions approaching those of the X-ray experiment. There are two difficulties in the EM approach: One is that the particles important for assembly are usually small and not very regular and therefore tend to be overlooked. Secondly EM specimens require low concentrations which favor disassembly of the particles one wants to observe since there is a dynamic equilibrium between polymers and subunits.

The CM120 Biotwin: a high-contrast objective lens, optimum cryo-vacuum and improved EDX performance

1995 ◽  
Vol 53 ◽  
pp. 584-585
Author(s):  
Uwe Lücken ◽  
Michael Felsmann ◽  
Wim M. Busing ◽  
Frank de Jong
Keyword(s):  
Life Science ◽  
Focal Length ◽  
Objective Lens ◽  
High Contrast ◽  
Contrast Imaging ◽  
X Ray ◽  
Forming Mechanism ◽  
Similar Image ◽  
High Contrast Imaging ◽  
Low Concentrations

A new microscope for the study of life science specimen has been developed. Special attention has been given to the problems of unstained samples, cryo-specimens and x-ray analysis at low concentrations.A new objective lens with a Cs of 6.2 mm and a focal length of 5.9 mm for high-contrast imaging has been developed. The contrast of a TWIN lens (f = 2.8 mm, Cs = 2 mm) and the BioTWTN are compared at the level of mean and SD of slow scan CCD images. Figure 1a shows 500 +/- 150 and Fig. 1b only 500 +/- 40 counts/pixel. The contrast-forming mechanism for amplitude contrast is dependent on the wavelength, the objective aperture and the focal length. For similar image conditions (same voltage, same objective aperture) the BioTWIN shows more than double the contrast of the TWIN lens. For phasecontrast specimens (like thin frozen-hydrated films) the contrast at Scherzer focus is approximately proportional to the √ Cs.

Localization of calcium and zinc in the sperm storage tubules of chicken, quail and turkey using X-ray microanalysis

Reproduction ◽  
2000 ◽  
pp. 331-336 ◽  
Author(s):  
L Holm ◽  
H Ekwall ◽  
GJ Wishart ◽  
Y Ridderstrale
Keyword(s):  
Calcium Concentration ◽  
Sperm Storage ◽  
X Ray ◽  
Elemental Concentrations ◽  
Low Concentrations ◽  
Intracellular Content ◽  
Wet Weight ◽  
The Mean ◽  
Sperm Storage Tubules ◽  
Scanning Electron

Sperm storage tubules from the utero-vaginal junction of chickens, quails and turkeys were analysed for calcium and zinc using X-ray microanalysis of ultra-rapidly frozen tissue in a scanning electron microscope. This technique enabled the tubular fluid surrounding the stored spermatozoa and the intracellular content of the cells of the sperm storage tubules to be analysed separately and, by using standards with known concentrations, their elemental concentrations were estimated. The mean (+/- SEM) concentration of calcium in the tubular fluid from chickens, quails and turkeys was 17 +/- 3, 19 +/- 3 and 17 +/- 4 mmol kg(-1) wet weight, respectively. The intracellular calcium concentration of the cells of the tubules did not differ significantly from these values and was also similar in the mucosal epithelial cells of the utero-vaginal junction. Zinc was localized in the cells of turkey sperm storage tubules and tubular fluid, but at low concentrations. No zinc could be detected in corresponding structures from chickens and quails. The concentration of calcium in the tubular fluid is within the range known to inhibit the motility of spermatozoa, supporting this function for calcium during storage. Zinc is known to depress turkey sperm metabolism and it may also be involved in inducing quiescence of spermatozoa during storage in this species.

scholarly journals X-ray, DTA and Raman studies of monoclinic tridymite and its higher temperature orthorhombic modification with varying temperature

2005 ◽  
Vol 100 (2) ◽  
pp. 55-69 ◽  
Author(s):  
Tadayuki HIROSE ◽  
Kuniaki KIHARA ◽  
Masayuki OKUNO ◽  
Syuhei FUJINAMI ◽  
Keiji SHINODA
Keyword(s):  
X Ray ◽  
Orthorhombic Modification ◽  
Higher Temperature

scholarly journals New Insights into the Crystal Chemistry of Elpidite, Na2Zr[Si6O15]·3H2O and (Na1+YCax□1−X−Y)Σ=2Zr[Si6O15]·(3−X)H2O, and Ab Initio Modeling of IR Spectra

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2160
Author(s):  
Alexander Bogdanov ◽  
Ekaterina Kaneva ◽  
Roman Shendrik
Keyword(s):  
Ir Spectra ◽  
Structural Models ◽  
Chemical Characterization ◽  
Chemical Compositions ◽  
X Ray Diffraction ◽  
Special Group ◽  
X Ray ◽  
Influence Of Water ◽  
Radioactive Species

Elpidite belongs to a special group of microporous zirconosilicates, which are of great interest due to their capability to uptake various molecules and ions, e.g., some radioactive species, in their structural voids. The results of a combined electron probe microanalysis and single-crystal X-ray diffraction study of the crystals of elpidite from Burpala (Russia) and Khan-Bogdo (Mongolia) deposits are reported. Some differences in the chemical compositions are observed and substitution at several structural positions within the structure of the compounds are noted. Based on the obtained results, a detailed crystal–chemical characterization of the elpidites under study was carried out. Three different structure models of elpidite were simulated: Na2ZrSi6O15·3H2O (related to the structure of Russian elpidite), partly Ca-replaced Na1.5Ca0.25ZrSi6O15·2.75H2O (close to elpidite from Mongolia), and a hypothetical CaZrSi6O15·2H2O. The vibration spectra of the models were obtained and compared with the experimental one, taken from the literature. The strong influence of water molecule vibrations on the shape of IR spectra of studied structural models of elpidite is discussed in the paper.

Silicate-germanate K2Y[(Si3Ge)O10(OH)] with unusual complex corrugated layer and its correlation to ring silicate gerenite and chain silicate chkalovite

2020 ◽  
Vol 235 (4-5) ◽  
pp. 167-172
Author(s):  
Anastasiia P. Topnikova ◽  
Elena L. Belokoneva ◽  
Olga V. Dimitrova ◽  
Anatoly S. Volkov ◽  
Leokadiya V. Zorina
Keyword(s):  
Low Temperature ◽  
Cross Section ◽  
Complex Anion ◽  
Diffraction Experiment ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Chain Silicate ◽  
Novel Complex

AbstractA new silicate-germanate K2Y[(Si3Ge)O10(OH)] was synthesized hydrothermally in a system Y2O3:GeO2:SiO2 = 1:1:2 (T = 280 °C; P = 90–100 atm.); K2CO3 was added to the solution as a mineralizer. Single-crystal X-ray diffraction experiment was carried out at low temperature (150 K). The unit cell parameters are a = 10.4975(4), b = 6.9567(2), c = 15.4001(6) Å, β = 104.894(4)°; V = 1086.86(7) Å3; space group is P 21/c. A novel complex anion is presented by corrugated (Si,Ge) tetrahedral layers connected by couples of YO6 octahedra into the mixed microporous framework with the channels along b and a axes, the maximal size of cross-section is ~5.6 Å. This structure has similarity with the two minerals: ring silicate gerenite (Ca,Na)2(Y,REE)3Si6O18 · 2H2O and chain silicate chkalovite Na2BeSi2O6. Six-member rings with 1̅ symmetry as in gerenite are distinguished in the new layer. They are mutually perpendicular to each other and connected by additional tetrahedra. Straight crossing chains in chkalovite change to zigzag four-link chains in the new silicate-germanate layer.

Luminescent Properties of Zn2SiO4:Eu3+,Dy3+ Phosphors via Sol-Gel Process

2012 ◽  
Vol 217-219 ◽  
pp. 733-736
Author(s):  
Xiu Mei Han ◽  
Shu Ai Hao ◽  
Ying Ling Wang ◽  
Gui Fang Sun ◽  
Xi Wei Qi
Keyword(s):  
Thermal Analysis ◽  
Ir Spectra ◽  
Sol Gel ◽  
Luminescent Properties ◽  
Photoluminescence Spectra ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sol Gel Process ◽  
Ft Ir

Zn2SiO4:Eu3+, Dy3+ phosphors have been prepared through the sol-gel process. X-ray diffraction (XRD), thermogravimetric and ddifferential thermal analysis (TG-DTA), FT-IR spectra and photoluminescence spectra were used to characterize the resulting phosphors. The results of XRD indicated that the phosphors crystallized completely at 1000oC. In Zn2SiO4:Eu3+,Dy3+ phosphors, the Eu3+ and Dy3+ show their characteristic red(613nm, 5D0-7F2), blue (481nm, 4F9/2–6H15/2) and yellow (577nm, 4F9/2–6H13/2) emissions.

Chiral Resolution of Hexaamine Cobalt(III) Cages: Substituent Effects on Chiral Discrimination

2003 ◽  
Vol 56 (12) ◽  
pp. 1187 ◽  
Author(s):  
Paul V. Bernhardt ◽  
Tri Erny Dyahningtyas ◽  
Jack M. Harrowfield ◽  
Jee-Young Kim ◽  
Yang Kim ◽  
...  
Keyword(s):  
Complex Anion ◽  
Substituent Effects ◽  
Outer Sphere ◽  
Exchange Chromatography ◽  
Chiral Resolution ◽  
Chiral Discrimination ◽  
Pairing Interaction ◽  
X Ray ◽  
Selective Crystallization ◽  
Bonding Interaction

Chiral resolution of the cobalt cage complexes [Co(diNOsar)]3+ and [Co(diAMsarH2)]5+ have been achieved by selective crystallization with the anion bis-μ-(R), (R)-tartratodiantimonate(III) ([Sb2(R,R-tart)2]2–) and also by column chromatography with Na2[Sb2(R,R-tart)2] as eluent. The X-ray crystal structures of Λ-[Co(diNOsar)][Sb2(R,R-tart)2]Cl . 7 H2O and Δ-[Co(diAMsarH2)][Sb2(R,R-tart)2]2Cl . 14 H2O are reported, which reveal an unexpected reversal of chiral discrimination when the cage substituent is changed from nitro (Λ-enantiomer) to ammonio Δ-enantiomer) and shows that the ammonio-substituted cage is capable of forming a three-point hydrogen-bonding interaction with each complex anion, whereas the nitro analogue can only form two hydrogen bonds with each [Sb2(R,R-tart)2]2– anion. During cation exchange chromatography of the racemic cobalt cage complexes with Na2[Sb2(R,R-tart)2] as eluent, Λ-[Co(diNOsar)]3+ elutes first, which implies a tighter ion pairing interaction than for the Δ-enantiomer. On the other hand, Δ-[Co(diAMsarH2)]5+ elutes first during chromatography under identical conditions, which is also consistent with a preferred outer-sphere complex formed between Δ-[Co(diAMsarH2)]5+ and [Sb2(R,R-tart)2]2– relative to Λ-[Co(diAMsarH2)]5+ and [Sb2(R,R-tart)2]2–.

The direct electrochemical synthesis of some metal derivatives of lapachol

1997 ◽  
Vol 75 (5) ◽  
pp. 499-506 ◽  
Author(s):  
E.H. De Oliveira ◽  
G.E.A. Medeiros ◽  
C. Peppe ◽  
Martyn A. Brown ◽  
Dennis G. Tuck
Keyword(s):  
Electrochemical Oxidation ◽  
Copper Atom ◽  
Electrochemical Synthesis ◽  
Acetonitrile Solution ◽  
Triclinic Space Group ◽  
X Ray ◽  
Metal Anode ◽  
X Ray Crystallography ◽  
Metal Derivatives ◽  
Derivatives Of

The electrochemical oxidation of a sacrificial metal anode (M = Zn, Cd, Cu) in an acetonitrile solution of 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone, lapachol, C15H14O3 (=HL) gives ML2. The results are in keeping with earlier work on direct electrochemical synthesis in related systems. Adducts with 2,2′-bipyridine (bpy) and N,N,N′,N′-tetramethylethanediamine (tmen) have also been prepared. The structure of the 2,2′-bipyridine adduct of Cu(lapacholate)2 has been established by X-ray crystallography. The parameters are triclinic, space group [Formula: see text], a = 12.748(59) Å, b = 13.859(49) Å, c = 11.770(59) Å, α = 108.30(4)°, β = 108.08(3)°, γ = 68.94(3)°, Z = 2, R = 0.059 for 2256 unique reflections. The copper atom is in a distorted CuN2O2O2′ environment. The mechanism of the formation of this Cu(lapacholate)2 is discussed. Keywords: electrochemical synthesis, lapachol, X-ray crystallography, copper(II) complex.

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