Structural, Magnetic and Spectral Properties of Iron(II) and Nickel(II) Complexes of N1-(Pyridin-2-yl)-3,5-dimethylpyrazole

1989 ◽  
Vol 42 (5) ◽  
pp. 623 ◽  
Author(s):  
AT Baker ◽  
NJ Ferguson ◽  
HA Goodwin ◽  
AD Rae
Keyword(s):  
Ground State ◽  
Low Temperatures ◽  
Spectral Properties ◽  
Elevated Temperatures ◽  
Crystal Data ◽  
X Ray ◽  
Disordered Structures ◽  
Length Changes ◽  
Spin Species

Iron(II) and nickel(II) complexes of N1-(pyridin-2-yl)-3,5-dimethylpyrazole (L) are described. Salts of [FeL3]2+ undergo a reversible temperature-induced singlet (1A1) ↔ quintet (5T2) transition, both in the solid state and in solution. The singlet- quintet change in acetone solution is characterized by ΔH = 25 � 2 kJ mol-1 and ΔS = 95 � 5 J K-1 mol-1. Mossbauer spectral data for solid [FeL3] [BF4]2 confirm a change in ground state for the metal atom with change in temperature and indicate two low-spin species at low temperatures and two high-spin species at elevated temperatures. The average M-N bond length changes accompanying the spin change have been estimated as 0.19 � from data obtained by determination of the structures of [FeL3][ClO4]2 at 135 K and 294 K and of [NiL3][BF4]2 at 294 K by single-crystal X-ray diffractometry. The crystals were all refined as disordered structures in space group P3c1 with Z = 2. Crystal data: [FeL3] [ClO4]2 at 294 K, a = b 10.489(2), 17.521(5) � ;[FeL3][ClO4]2 at 135 K, a = b 10.355(3), c 17.464(5) � ; [NiL3] [BF4]2 at 294 K, a = b 10.404(3), c 17.618(8) � .

Coordination of 2,2'-Bithiazole. Spectral, Magnetic and Structural Studies of the Iron(II) and Nickel(II) Complexes

1988 ◽  
Vol 41 (11) ◽  
pp. 1625 ◽  
Author(s):  
DC Craig ◽  
HA Goodwin ◽  
D Onggo ◽  
AD Rae
Keyword(s):  
High Spin ◽  
Spectral Properties ◽  
Elevated Temperatures ◽  
Spin Transition ◽  
Anomalous Temperature ◽  
Space Group ◽  
X Ray ◽  
Spin Lattice ◽  
Centrosymmetric Space Group ◽  
Spin Species

Iron(II) and nickel(II) complexes of 2,2′bithiazole (2bt) have been prepared. Salts of [Fe(2bt)3]2+ have spectral properties typical of iron(II) diimine systems. Their magnetic and Mossbauer spectral properties show an anomalous temperature-dependence which is associated with a temperature-induced singlet (1A1) ↔ quintet (5T2) transition. The manifestation of the spin transition is complicated by the existence of two modifications of the complex perchlorate. In one of these there is a relatively small fraction of quintet state species in an essentially low-spin lattice. This fraction increases only slightly at elevated temperatures within the range 89-343 K. The other modification is essentially high-spin at high temperatures and low-spin at low temperatures. The quadrupole splitting values for the two high-spin species are quite different, arising from different lattice contributions. The structures of 2bt and the related 4,4′-bithiazole and of [Ni(2bt)3][ClO4]2 have been determined by single-crystal X-ray diffactometry. These afford a comparison of the coordination features of the isomeric bithiazoles. 2,2′-Bithiazole, orthorhombic with space group P bca , Z = 8, α 9.284(1), b 14.564(1), c 10.802(1) Ǻ; 4,4′-Bithiazole, monoclinic with space group P21/c, Z = 2, a 5.528(2), b 6.288(2), c 11.316(4)Ǻ. The nickel complex, orthorhombic with non-centrosymmetric space group Pna21, four molecules per unit cell, a 16.709(3), b 9.511(4), c 17.491(2)Ǻ, has a stacking fault which reduces the intensity of h = 2n+1 data. Pseudosymmetry enables data with h = 2n to be described by a disordered structure in the centrosymmetric space group Pnmn.

Low-temperature crystallization and structure determination of N-(trifluoromethyl)formamide, N-(2,2,2-trifluoroethyl)formamide and 2,2,2-trifluoroethyl isocyanide

1999 ◽  
Vol 55 (1) ◽  
pp. 70-77 ◽  
Author(s):  
G. J. Perpétuo ◽  
J. Buschmann ◽  
P. Luger ◽  
D. Lentz ◽  
D. Dreissig
Keyword(s):  
Crystal Structure ◽  
Low Temperatures ◽  
Crystal Packing ◽  
Crystal Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Low Temperature Crystallization ◽  
Temperature Crystallization

Crystals of N-(trifluoromethyl)formamide, C2H2F3NO, (I), N-(2,2,2-trifluoroethyl)formamide, C3H4F3NO, (II), and 2,2,2-trifluoroethyl isocyanide, C3H2F3N, (III), were grown in situ on an X-ray diffractometer and analysed by single-crystal X-ray diffraction methods at low temperatures. Crystal data: (I) orthorhombic, P212121, a = 4.547 (2) Å, b = 5.947 (3) Å, c = 14.731 (9) Å, V = 398.3 (4) Å3, Z = 4, M r = 113.05, T = 143 K, D x = 1.885 Mg m−3; (II) monoclinic, P21/n, a = 4.807 (1) Å, b = 16.707 (3) Å, c = 6.708 (1) Å, β = 109.90 (1)°, V = 506.6 (2) Å3, Z = 4, M r = 127.07, T = 141 K, D x = 1.666 Mg m−3; (III) orthorhombic, P212121, a = 5.668 (2) Å, b = 9.266 (3) Å, c = 8.626 (2) Å, V = 453.0 (2) Å3, Z = 4, M r = 109.06, T = 163 K, D x = 1.599 Mg m−3. The results showed that in the crystal both formamides (I) and (II) are exclusively present in the form of the Z isomer, although measurements of solutions of (I) have shown that the E isomer prevails [Lentz et al. (1987). Angew. Chem. 99, 951–953]. In addition ab initio calculations for (I) predicted the E isomer to be the more stable one. In compound (III) the isocyanide group is staggered with respect to the trifluoroethyl group. In the crystal packing of (I) and (II) intermolecular N—H\cdotsO hydrogen bonds generate infinite chains. In (I), these chains are linked to form sheets by C—H\cdotsO contacts. In the crystal structure of (III) each isocyanide dipole is surrounded by four electronegative F atoms with intermolecular C\cdotsF contacts between 3.4 and 3.5 Å.

Vibronische Kopplung und dynamisch verzerrte Strukturen in Hexahalogenotelluraten(IV): Ergebnisse aus Tieftemperatur-Röntgenbeugungsuntersuchungen (300—160 K) und aus FTIR-spektroskopischen Experimenten (300—5 K) [1] / Vibronic Coupling and Dynamically Distorted Structures in Hexahalogenotellurates(IV): Low Temperatur X-Ray Diffraction (300—160 K) and FTIR-Spectroscopic (300—5 K) Results [1]

1987 ◽  
Vol 42 (10) ◽  
pp. 1273-1281 ◽  
Author(s):  
Walter Abriel ◽  
Ernst-Jürgen Zehnder
Keyword(s):  
Ground State ◽  
Low Temperatures ◽  
Potential Surface ◽  
Energy Gap ◽  
Vibronic Coupling ◽  
High Symmetry ◽  
X Ray Diffraction ◽  
X Ray ◽  
First Excited State ◽  
Theoretical Considerations

AbstractFrom theoretical considerations a dynamically distorted octahedron as a result of vibronic coupling between the ground state and the first excited state should exist for 14 electron AX6E systems like TeX62- . A high symmetry crystal field yielding at least a center of symmetry for the Te position stabilizes this fluctuating structure, otherwise statical distortion will be observed. From X-ray diffraction experiments on antifluorite type compounds A2TeX6 (A = Rb. Cs: X = Cl, Br) the averaged structure (m3̅m symmetry) of the anions was found even at very low temperatures. The thermal parameters are not significantly different from those of similar SnX62 compounds. Distortions therefore are very small and are evident from FTIR spectroscopic meas­urements only. Here very broad T1u-deformation vibration bands are observed down to tempera­tures <10 K without splitting: Astatically distorted species could not be frozen out. In contrast to XeF6 for TeX62- the energy gap between the threefold, fourfold or sixfold minima of the potential surface (according to the symmetry of one component of the T1u-vibration) is very small and shifted to temperatures lower than reached with the devices used for these experiments.

THE INTERPLAY OF PROMPT AND AFTERGLOW EMISSION IN GRB 060418

2008 ◽  
Vol 17 (09) ◽  
pp. 1343-1349 ◽  
Author(s):  
S. D. VERGANI ◽  
D. MALESANI ◽  
E. MOLINARI
Keyword(s):  
Gamma Rays ◽  
Spectral Properties ◽  
Gamma Ray ◽  
Early Time ◽  
Lorentz Factor ◽  
X Ray ◽  
Central Engine ◽  
Low Energies ◽  
Prompt Emission

We present observations of the early afterglow emission of GRB 060418. Thanks to the simultaneous coverage at optical, X-ray and gamma-ray wavelengths, we can detect and separate the external shock emission (visible in the optical and late X-ray data) and the central engine activity (early X and gamma rays). The two components are clearly distinguished based on temporal and spectral properties. The detection of the afterglow onset (in the optical) allows the determination of the fundamental fireball properties, namely its bulk Lorentz factor and total energy. The early time X-ray flare closely resembles the prompt emission gamma-ray pulses in its temporal profile, being wider at low energies and showing lags between the hard and soft bands. This provides a strong suggestion that X-ray flares are a continuation of the prompt emission.

Kristallzucht und Strukturaufklärung von K2[Pt(CN)4Cl2], K2[Pt(CN)4Br2], K2[Pt(CN)4I2] und K2[Pt(CN)4Cl2] · 2H2O/ Crystal Growth and Crystal Structure Determination of K2[Pt(CN)4Cl2], K2[Pt(CN)4Br2], K2[Pt(CN)4I2] and K2[Pt(CN)4]Cl2] · 2H2O

2004 ◽  
Vol 59 (5) ◽  
pp. 567-572 ◽  
Author(s):  
Claus Mühle ◽  
Andrey Karpov ◽  
Jürgen Nuss ◽  
Martin Jansen
Keyword(s):  
Crystal Structure ◽  
Infrared Spectroscopy ◽  
Crystal Growth ◽  
Single Crystal ◽  
Structure Determination ◽  
Spectroscopy Data ◽  
Crystal Data ◽  
X Ray ◽  
Raman And Infrared Spectroscopy

Abstract Crystals of K2Pt(CN)4Br2, K2Pt(CN)4I2 and K2Pt(CN)4Cl2 ·2H2O were grown, and their crystal structures have been determined from single crystal data. The structure of K2Pt(CN)4Cl2 has been determined and refined from X-ray powder data. All compounds crystallize monoclinicly (P21/c; Z = 2), and K2Pt(CN)4X2 with X = Cl, Br, I are isostructural. K2Pt(CN)4Cl2: a = 708.48(2); b = 903.28(3); c = 853.13(3) pm; β = 106.370(2)°; Rp = 0.064 (N(hkl) = 423). K2Pt(CN)4Br2: a = 716.0(1); b = 899.1(1); c = 867.9(1) pm; β = 106.85(1)°; R(F)N′ = 0.026 (N’(hkl) = 3757). K2Pt(CN)4I2: a = 724.8(1); b = 914.5(1); c = 892.1(1) pm; β = 107.56(1)°; R(F)N′ = 0.025 (N’(hkl) = 2197). K2Pt(CN)4Cl2 ·2H2O: a = 763.76(4); b = 1143.05(6); c = 789.06(4) pm; β = 105.18(1)°; R(F)N′ = 0.021 (N’(hkl) = 2281). Raman and infrared spectroscopy data are reported.

Evolution of Ce-Valence in Ce-Rh-Si Compounds: Intermediate Valence in CeRh6Si4

2016 ◽  
Vol 257 ◽  
pp. 199-202
Author(s):  
Thomas Gruner ◽  
Christoph Geibel
Keyword(s):  
Ground State ◽  
Low Temperatures ◽  
Ternary Phase ◽  
Ternary Phase Diagram ◽  
Intermediate Valence ◽  
Characteristic Energy ◽  
X Ray ◽  
Resistivity Measurements ◽  
Intermediate Valent ◽  
X Ray Absorption

We synthesized polycrystalline samples of CeRh6Si4 and investigated its physical properties by means of magnetic susceptibility, specific heat and electrical resistivity measurements as well as LIII X-ray absorption spectroscopy. All results evidence an intermediate-valent (IV) Ce state with a valence close to 3.2 and a characteristic energy of about 300 K. Accordingly, we observe a Fermi liquid ground state at low temperatures with a slightly enhanced Sommerfeld coefficient γ = 28 mJ/molK2. Using presently available data on different compounds, we analyze the evolution of the Ce valence in the Ce-Rh-Si ternary phase diagram. The expected correlation with the distance to nearest Ce-ligands can be discerned. Thus, the evolution from a trivalent Ce3+ state in CeRh3Si2 to an IV state in CeRh6Si4 is related to a shortening of both the Ce-Rh and Ce-Si bonds in the first coordination sphere of Ce.

scholarly journals Redetermination of K2Mg3(OH)2(SO4)3(H2O)2 from single-crystal X-ray data revealing the correct hydrogen-atom positions

2021 ◽  
Vol 77 (1) ◽  
pp. 62-65
Author(s):  
Matthias Weil
Keyword(s):  
Hydrogen Bond ◽  
Single Crystal ◽  
Crystal Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Accuracy And Precision ◽  
Medium Strength ◽  
Anisotropic Displacement Parameters ◽  
Bonding Scheme

In comparison with the previous structure determination of K2Mg3(OH)2(SO4)3(H2O)2, dipotassium trimagnesium dihydroxide tris(sulfate) dihydrate, from laboratory powder X-ray diffraction data [Kubel & Cabaret-Lampin (2013). Z. Anorg. Allg. Chem. 639, 1782–1786], the present redetermination against CCD single-crystal data has allowed for the modelling of all non-H atoms with anisotropic displacement parameters. As well as higher accuracy and precision in terms of bond lengths and angles, the clear localization of the H-atom positions leads also to a reasonable hydrogen-bonding scheme for this hydroxy hydrate. The structure consists of (100) sheets composed of corner- and edge-sharing [MgO6] octahedra and sulfate tetrahedra. Adjacent sheets are linked by the potassium cations and a hydrogen bond of medium strength involving the water molecule. The title compound is isotypic with its CoII and MnII analogues: the three K2 M 3(OH)2(SO4)3(H2O)2 (M = Mg, Co, Mn) structures are quantitatively compared.

Coordination of 3,3'-Bipyridazine With Bivalent Copper, Palladium and Platinum

1990 ◽  
Vol 43 (11) ◽  
pp. 1919 ◽  
Author(s):  
HA Goodwin ◽  
D Onggo ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Vibrational Spectra ◽  
Complex Cation ◽  
Monoclinic Space Group ◽  
Crystal Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Planar Conformation ◽  
Bivalent Copper ◽  
Electronic And Vibrational Spectra

Bis ( ligand ) complexes of the diimine 3,3′-bipyridazine (L) with bivalent copper, palladium and platinum are described. Green and violet forms of [CuL2] [BF4]2 were obtained, and the electronic and vibrational spectra suggest coordinated fluoroborate groups in the violet species. In the green complex a tetragonal structure is indicated. Coordination of perchlorate in [PdL2] [ClO4]2 is also indicated but not in [PtL2] [ClO4]2. Structure determination of the latter complex reveals a strictly planar PtN4 moiety, and in fact the whole complex cation is approximately planar. Reduced interligand repulsions, compared to those operative in bis ( ligand ) complexes of 2,2?-bipyridine, are believed to allow the essentially planar conformation. The structure of [PtL2] [ClO4]2 was determined at 295 K by single-crystal X-ray diffraction methods, and was refined to a residual of 0.033 for 1942 'observed' independent reflections. Crystal data: [PtL2][ClO4]2 monoclinic, space group P21/c (C5/2h, No. 14), a 7.919(2), b 13.086(3), c 10.313(3)Ǻ, β 107.16(2)°.

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