Transition Metal Azolates from Metallocenes. 2. Synthesis, X-ray Structure, and Magnetic Properties of a Three-Dimensional Polymetallic Iron(II) Imidazolate Complex, a Low-Temperature Weak Ferromagnet

1997 ◽  
Vol 119 (37) ◽  
pp. 8675-8680 ◽  
Author(s):  
Steven J. Rettig ◽  
Alan Storr ◽  
David A. Summers ◽  
Robert C. Thompson ◽  
James Trotter
2006 ◽  
Vol 985 ◽  
Author(s):  
Tori Z. Forbes ◽  
Peter C. Burns ◽  
L. Soderholm ◽  
S. Skanthakumar

AbstractSingle crystals of Np2O5 have been synthesized by low-temperature hydrothermal reaction of a Np5+ stock solution with natural calcite crystals. The structure of Np2O5 was solved by direct methods and refined on the basis of F2 for all unique data collected on a Bruker X-ray diffractometer equipped with an APEX II CCD detector. Np2O5 is monoclinic, space group P2/c, with a = 8.168(2) Å, b = 6.584(1) Å, c = 9.3130(2) Å, β = 116.01(1)˚, V = 449.8(2) Å3, and Z = 1. The structure contains chains of edge-sharing neptunyl pentagonal bipyramids linked into sheets through cation-cation interactions with distorted neptunyl square bipyramids. Additional cation-cation interactions connect the sheets into a three-dimensional framework. The formation of Np2O5 on the surface of calcite crystals has important implications for the precipitation of isolated neptunyl phases in natural aqueous systems.


2005 ◽  
Vol 60 (8) ◽  
pp. 821-830 ◽  
Author(s):  
Jan F. Riecken ◽  
Gunter Heymann ◽  
Theresa Soltner ◽  
Rolf-Dieter Hoffmann ◽  
Hubert Huppertz ◽  
...  

The high-pressure (HP) modification of CePtSn was prepared under multianvil high-pressure (9.2 GPa) high-temperature (1325 K) conditions from the normal-pressure (NP) modification. Both modifications were investigated by powder and single crystal X-ray data: TiNiSi type, Pnma, a = 746.89(9), b = 462.88(4), c = 801.93(7) pm, wR2 = 0.0487, 452 F2 values, 20 variable parameters for NP-CePtSn, and ZrNiAl type, P6̅2m, a = 756.919(5), c = 415.166(4) pm, wR2 = 0.0546, 252 F2 values, 14 variable parameters for HP-CePtSn. Both modifications are built up from platinumcentered trigonal prisms. Together, the platinum and tin atoms form different three-dimensional [PtSn] networks in which the cerium atoms fill channels. The crystal chemistry and chemical bonding of NP- and HP-CePtSn is discussed. Susceptibility measurements of HP-CePtSn indicate Curie-Weiss behavior above 40 K with an experimental magnetic moment of 2.55(1) μB/Ce atom, indicating trivalent cerium. No magnetic ordering could be detected down to 2 K.


2008 ◽  
Vol 63 (9) ◽  
pp. 1127-1130 ◽  
Author(s):  
Falko M. Schappacher ◽  
Ute Ch. Rodewald ◽  
Rainer Pöttgen

New intermetallic compounds RE4TCd (RE = Y, La-Nd, Sm, Gd-Tm, Lu; T = Ni, Pd, Ir, Pt) were synthesized by melting of the elements in sealed tantalum tubes in a highfrequency furnace. They crystallize with the Gd4RhIn-type structure, space group F 4̄3m, Z = 16. The four gadolinium compounds were characterized by single crystal X-ray diffractometer data: a = 1361.7(1) pm, wR2 = 0.062, 456 F2 values, 19 variables for Gd4NiCd; a = 1382.1(2) pm, wR2 = 0.077, 451 F2 values, 19 variables for Gd4PdCd; a = 1363.6(2) pm, wR2 = 0.045, 494 F2 values, 19 variables for Gd4IrCd; a = 1379.0(1) pm, wR2 = 0.045, 448 F2 values, 19 variables for Gd4PtCd. The rare earth atoms build up transition metal-centered trigonal prisms which are condensed via common corners and edges, leading to three-dimensional adamantane-related networks. The cadmium atoms form Cd4 tetrahedra which fill voids left in the prisms’ network.


2000 ◽  
Vol 39 (8) ◽  
pp. 1803-1808 ◽  
Author(s):  
Carlo Bellitto ◽  
Fulvio Federici ◽  
Angela Altomare ◽  
Rosanna Rizzi ◽  
Said A. Ibrahim

Author(s):  
Bei Zhang ◽  
Gangxing Guo ◽  
Fang Lu ◽  
Ying Song ◽  
Yong Liu ◽  
...  

Low temperature is a major limiting factor for plant growth and development. Dehydrin proteins are generally induced in response to low-temperature stress. In previous research, a full-length dehydrin gene,PicW2, was isolated fromPicea wilsoniiand its expression was associated with hardiness to cold. In order to gain insight into the mechanism of low-temperature tolerance by studying its three-dimensional crystal structure, prokaryotically expressed PicW2 dehydrin protein was purified using chitosan-affinity chromatography and gel filtration, and crystallized using the vapour-diffusion method. The crystal grew in a condition consisting of 0.1 MHEPES pH 8.0, 25%(w/v) PEG 3350 using 4 mg ml−1protein solution at 289 K. X-ray diffraction data were collected from a crystal at 100 K to 2.82 Å resolution. The crystal belonged to space groupC121, with unit-cell parametersa= 121.55,b= 33.26,c= 73.39 Å, α = γ = 90.00, β = 109.01°. The asymmetric unit contained one molecule of the protein, with a corresponding Matthews coefficient of 2.87 Å3 Da−1and a solvent content of 57.20%. Owing to a lack of structures of homologous dehydrin proteins, molecular-replacement trials failed. Data collection for selenium derivatization of PicW2 and crystal structure determination is currently in progress.


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