scholarly journals High-Pressure Crystal Structure and Unusual Magnetoresistance of a Single-Component Molecular Conductor [Pd(dddt)2] (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate)

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 534
Author(s):  
Hengbo Cui ◽  
Hamish H.-M. Yeung ◽  
Yoshitaka Kawasugi ◽  
Takaaki Minamidate ◽  
Lucy K. Saunders ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Three Dimensional ◽  
Structural Disorder ◽  
Electron System ◽  
Experimental Information ◽  
Crystal Structure Analysis ◽  
Single Component ◽  
Unusual Behavior ◽  
Dirac Electron

A single-component molecular crystal [Pd(dddt)2] has been shown to exhibit almost temperature-independent resistivity under high pressure, leading theoretical studies to propose it as a three-dimensional (3D) Dirac electron system. To obtain more experimental information about the high-pressure electronic states, detailed resistivity measurements were performed, which show temperature-independent behavior at 13 GPa and then an upturn in the low temperature region at higher pressures. High-pressure single-crystal structure analysis was also performed for the first time, revealing the presence of pressure-induced structural disorder, which is possibly related to the changes in resistivity in the higher-pressure region. Calculations based on the disordered structure reveal that the Dirac cone state and semiconducting state coexist, indicating that the electronic state at high pressure is not a simple Dirac electron system as previously believed. Finally, the first measurements of magnetoresistance on [Pd(dddt)2] under high pressure are reported, revealing unusual behavior that seems to originate from the Dirac electron state.

Single-component molecular conductor [Pt(dmdt)2]—a three-dimensional ambient-pressure molecular Dirac electron system

2019 ◽  
Vol 55 (23) ◽  
pp. 3327-3330 ◽  
Author(s):  
Biao Zhou ◽  
Shoji Ishibashi ◽  
Tatsuru Ishii ◽  
Takahiko Sekine ◽  
Ryosuke Takehara ◽  
...  
Keyword(s):  
Ambient Pressure ◽  
Three Dimensional ◽  
Electron System ◽  
Single Component ◽  
Nodal Lines ◽  
Molecular Conductor ◽  
System P ◽  
Dirac Electron

[Pt(dmdt)2], an air-stable single-component molecular conductor, contains massless Dirac electrons and carries Dirac nodal lines at ambient pressure.

Emergence of the Dirac Electron System in a Single-Component Molecular Conductor under High Pressure

2017 ◽  
Vol 139 (5) ◽  
pp. 1770-1773 ◽  
Author(s):  
Reizo Kato ◽  
HengBo Cui ◽  
Takao Tsumuraya ◽  
Tsuyoshi Miyazaki ◽  
Yoshikazu Suzumura
Keyword(s):  
High Pressure ◽  
Electron System ◽  
Single Component ◽  
Molecular Conductor ◽  
Dirac Electron

Crystal Structure Analysis of Cu-Zr Alloys by Convergent Beam Diffraction

1981 ◽  
Vol 39 ◽  
pp. 354-355
Author(s):  
A. F. Marshall ◽  
J. W. Steeds ◽  
D. Bouchet ◽  
S. L. Shinde ◽  
R. G. Walmsley
Keyword(s):  
Crystal Structure ◽  
Point Group ◽  
Intermetallic Phase ◽  
Three Dimensional ◽  
Crystal Structure Analysis ◽  
Ion Milling ◽  
Composition And Structure ◽  
Unit Cells ◽  
Sputter Deposited ◽  
Convergent Beam

Convergent beam electron diffraction is a powerful technique for determining the crystal structure of a material in TEM. In this paper we have applied it to the study of the intermetallic phases in the Cu-rich end of the Cu-Zr system. These phases are highly ordered. Their composition and structure has been previously studied by microprobe and x-ray diffraction with sometimes conflicting results.The crystalline phases were obtained by annealing amorphous sputter-deposited Cu-Zr. Specimens were thinned for TEM by ion milling and observed in a Philips EM 400. Due to the large unit cells involved, a small convergence angle of diffraction was used; however, the three-dimensional lattice and symmetry information of convergent beam microdiffraction patterns is still present. The results are as follows:1) 21 at% Zr in Cu: annealed at 500°C for 5 hours. An intermetallic phase, Cu3.6Zr (21.7% Zr), space group P6/m has been proposed near this composition (2). The major phase of our annealed material was hexagonal with a point group determined as 6/m.

The first crystal structure of the peptidase domain of the U32 peptidase family

2015 ◽  
Vol 71 (12) ◽  
pp. 2505-2512 ◽  
Author(s):  
Magdalena Schacherl ◽  
Angelika A. M. Montada ◽  
Elena Brunstein ◽  
Ulrich Baumann
Keyword(s):  
Crystal Structure ◽  
Catalytic Mechanism ◽  
Quaternary Structure ◽  
Catalytic Domain ◽  
Three Dimensional ◽  
Zinc Ion ◽  
Crystal Structure Analysis ◽  
Dimensional Structure ◽  
Sequence Motifs ◽  
Conserved Sequence

The U32 family is a collection of over 2500 annotated peptidases in the MEROPS database with unknown catalytic mechanism. They mainly occur in bacteria and archaea, but a few representatives have also been identified in eukarya. Many of the U32 members have been linked to pathogenicity, such as proteins fromHelicobacterandSalmonella. The first crystal structure analysis of a U32 catalytic domain fromMethanopyrus kandleri(genemk0906) reveals a modified (βα)8TIM-barrel fold with some unique features. The connecting segment between strands β7 and β8 is extended and helix α7 is located on top of the C-terminal end of the barrel body. The protein exhibits a dimeric quaternary structure in which a zinc ion is symmetrically bound by histidine and cysteine side chains from both monomers. These residues reside in conserved sequence motifs. No typical proteolytic motifs are discernible in the three-dimensional structure, and biochemical assays failed to demonstrate proteolytic activity. A tunnel in which an acetate ion is bound is located in the C-terminal part of the β-barrel. Two hydrophobic grooves lead to a tunnel at the C-terminal end of the barrel in which an acetate ion is bound. One of the grooves binds to aStrep-Tag II of another dimer in the crystal lattice. Thus, these grooves may be binding sites for hydrophobic peptides or other ligands.

Crystal-to-Crystal Diastereoselective Transformation of 2,4,6-Triisopropyl-4'-(S)-phenylalaninocarbonylbenzophenone Methyl Ester

1998 ◽  
Vol 54 (6) ◽  
pp. 907-911 ◽  
Author(s):  
H. Hosomi ◽  
Y. Ito ◽  
S. Ohba
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Methyl Ester ◽  
Absolute Configuration ◽  
Crystal Structure Analysis ◽  
X Ray Diffraction ◽  
Pass Filter ◽  
X Ray ◽  
Ultra High Pressure ◽  
Phenylalanine Methyl Ester

Dissymmetry of the photoproduct was induced by using a chiral substituent, (S)-methylphenylalanine, in the title compound {N-4-(2,4,6-triisopropylbenzoyl)benzoyl]-(S)-phenylalanine methyl ester (I)}. On irradiation with light from a 250 W ultra-high-pressure Hg lamp for 7 h through a long-pass filter, the photoreaction in a crystal was 100% complete without the loss of crystallinity. The crystal structures (I), before, and (II) {N-[4-(7-hydroxy-3,5-diisopropyl-8,8-dimethylbicyclo[4.2.0]octa-1,3,5-trien-7-yl)benzoyl]-(S)-phenylalanine methyl ester}, after photocyclization, have been determined by X-ray diffraction. For comparison, a crystal structure analysis has also been carried out for the photoproduct (III) of the 3′-COOMe derivative after recrystallization {methyl 3-(7-hydroxy-3,5-diisopropyl-8,8-dimethylbicyclo[4.2.0]octa-1,3,5-trien-7-yl)benzoate}. The dihedral angle between the central carbonyl plane and the triisopropylphenyl ring deviates from 90° by 10 (1)° in (I), which makes an imbalance in the intramolecular O(carbonyl)...H(methine) distances of the isopropyl groups at positions 2 and 6. The crystal structure of (II) indicates that the nearer methine H was predominantly abstracted by the carbonyl O atom in the reaction. The absolute configuration around the asymmetric C atom in the cyclobutenol ring of the product is S.

A fourfold interpenetrating diamond-like three-dimensional zinc(II) coordination polymer: synthesis, crystal structure and physical properties

2019 ◽  
Vol 75 (5) ◽  
pp. 504-507 ◽  
Author(s):  
Hui-Ru Chen
Keyword(s):  
Crystal Structure ◽  
Room Temperature ◽  
Three Dimensional ◽  
Fluorescence Emission ◽  
Crystal Structure Analysis ◽  
The Novel ◽  
X Ray Diffraction ◽  
Metal Compounds ◽  
X Ray ◽  
Coordination Framework

Excellent fluorescence properties are exhibited by d 10 metal compounds. The novel three-dimensional ZnII coordination framework, poly[[{μ2-bis[4-(2-methyl-1H-imidazol-1-yl)phenyl] ether-κ2 N 3:N 3′}(μ2-furan-2,5-dicarboxylato-κ2 O 2:O 5)zinc(II)] 1.76-hydrate], {[Zn(C6H2O5)(C20H18N4O)]·1.76H2O} n , has been prepared and characterized using IR spectroscopy, elemental analysis and single-crystal X-ray diffraction. The crystal structure analysis revealed that the compound exhibits a novel fourfold interpenetrating diamond-like network. This polymer also displays a strong fluorescence emission in the solid state at room temperature.

X-ray powder crystal structure analysis of high pressure tungsten dioxide. On the information in weak reflections

1994 ◽  
Vol 209 (8) ◽  
Author(s):  
M. Sundberg ◽  
P.-E. Werner ◽  
I. P. Zibrov
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Structure Analysis ◽  
Crystal Structure Analysis ◽  
X Ray

AbstractA high-pressure modification of tungsten dioxide (hp-WOIn the hp-WO

The stereochemistry of B -diketo complexes with trim ethylplatinum iv II. The crystal structure of ethyl(trim ethylplatini-)- acetoacetate

1960 ◽  
Vol 254 (1277) ◽  
pp. 218-228 ◽  
Keyword(s):  
Crystal Structure ◽  
Three Dimensional ◽  
Carbonyl Oxygen ◽  
Crystal Structure Analysis ◽  
Methyl Groups ◽  
Methylene Carbon ◽  
X Ray ◽  
Methylene Carbon Atom ◽  
Critical Account ◽  
Active Methylene

A three-dimensional X-ray crystal structure analysis of the complex between trimethyl platinum and ethylacetoacetate, (CH 3 ) 3 Pt CH 3 . CO. CH. CO OC 2 H 5 , has shown that the molecule is dimeric. In a monoclinic unit cell (a = 8.83, b = 14.12, c = 9.30 Å, β = 95°, space group P2 1 / c ) there are two centrosymmetrical dimeric molecules in which each platinum atom is octahedrally co-ordinated by three methyl groups, in the cis configuration, by the two carbonyl oxygen atoms of one β -ketoester and by the central, or ‘active methylene’ carbon atom of the other β -ketoester in the dimer. The structure is thus essentially the same as that of trimethyl 4:6-dioxononyl platinum (part I) and the result shows that complex formation via a tridentate β -diketo system is preferred to co-ordination through an ester oxygen. A critical account is given of the criteria used to judge the correctness of the results.

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