11,935 research outputs found
Synthesis and characterization of multiferroic BiMnO
We report on the high pressure synthesis of BiMnO, a manganite
displaying a "quadruple perovskite" structure. Structural characterization of
single crystal samples shows a distorted and asymmetrical coordination around
the Bi atom, due to presence of the lone pair, resulting in
non-centrosymmetric space group Im, leading to a permanent electrical dipole
moment and ferroelectric properties. On the other hand, magnetic
characterization reveals antiferromagnetic transitions, in agreement with the
isostructural compounds, thus evidencing two intrinsic properties that make
BiMnO a promising multiferroic material.Comment: 4 pages, 3 figure
Crystallographic disorder and electron scattering on structural two-level systems in ZrAs1.4Se0.5
Single crystals of ZrAs1.4Se0.5 (PbFCl type structure) were grown by chemical
vapour transport. While their thermodynamic and transport properties are
typical for ordinary metals, the electrical resistivity exhibits a shallow
minimum at low temperatures. Application of strong magnetic fields does not
influence this anomaly. The minimum of the resistivity in ZrAs1.4Se0.5
apparently originates from interaction between the conduction electrons and
structural two-level systems. Significant disorder in the As-Se substructure is
inferred from X-ray diffraction and electron microprobe studies
4-Nitro-2-{[(tricyclo[3.3.1.13,7]decan-1-yl)iminiumyl]methyl}phenolate
The title compound, C17H20N2O3, is a Schiff base, which is found as a zwitterion in the solid state. The geometry around the iminium N atom indicates sp
2-hybridization. The zwitterion shows a strong intramolecular N—H⋯O hydrogen-bond interaction between the iminium N atom and the phenolate O atom
A new triclinic modification of the pyrochlore-type KOs2O6 superconductor
A new modification of KOs2O6, the representative of a new structural type
(Pearson symbol aP18, a=5.5668(1)A, b=6.4519(2)A, c=7.2356(2)A, space group
P-1, no.2) was synthesized employing high pressure technique. Its structure was
determined by single-crystal X-ray diffraction. The structure can be described
as two OsO6 octahedral chains relating to each other through inversion and
forming big voids with K atoms inside. Quantum chemical calculations were
performed on the novel compound and structurally related cubic compound.
High-pressure X-ray study showed that cubic KOs2O6 phase was stable up to
32.5(2) GPa at room temperature.Comment: 23 pages, 9 figures,6 tables. Accepted for J. Solid State Che
1-(4-Bromo-3-chlorophenyl)-3-methoxy-3-methylurea (chlorbromuron)
In the title urea-based herbicide, C9H10BrClN2O2, there exist multiple inter- and intramolecular interactions. Most notably, the intramolecular hydrogen bond between the urea carbonyl O atom and an aromatic H atom affects the planarity and torsion angles of the molecule by restricting rotations about the Ar—secondary amine N and the secondary amine N and the carbonyl C. The two N atoms in the urea fragment are in different environments. One is planar; the other, pseudo-C
3v. It is likely that the different nitrogen-atom geometries and the restricted rotations within the molecule impact the bioactivity of chlorbromuron
Diethyl 2-[(1-methyl-1H-pyrrol-2-yl)methyleneamino]-5-(2-thienylmethyleneamino)thiophene-3,4-dicarboxylate
Both imine bonds of the title compound, C21H21N3O4S2, were found to be in the E configuration. The terminal pyrrole and thiophene rings are twisted by 2.5 (3) and 2.3 (2)°, respectively, from the mean plane of the central thiophene to which they are attached. The structure is disordered by exchange of the terminal heterocyclic rings; the site occupancy factors are ca 0.8 and 0.2. The crystal packing involves some π–π stacking [3.449 (4) Å between pyrrole and terminal thiophene rings]
CRYSTAL AND MOLECULAR-STRUCTURE OF 2',3',5'-TRI-O-ACETYL-6-O-(MESITYLENESULPHONYL)GUANOSINE
The structure of a 6-O-mesitylenesulphonyl derivative of 2',3',5'-tri-O-acetylguanosine, C 24 H 29 N50 10 S, has
been determined by X-ray diffraction. Crystals are monoclinic, a = 26.370 (4), b = 8.200 (2), c =
17.991 (3) A, fl = 132.77 (4) o. The solution of the structure in space group C2 was not straightforward and is
described in detail. Refinement converged at R = 0.110 for 1102 observed reflections. The guanine base
displays some deviations from its usual geometry due to the loss of C(6)-O(6) double-bond character. The
ribose sugar is C(2')-endo puckered
2,4-Diiodo-6-{[4-(morpholin-4-yl)phenyl]iminomethyl}phenol
In the title compound, C17H16I2N2O2, the two aromatic rings are almost coplanar [dihedral angle 2.57 (15)°]. The morpholine ring adopts a chair conformation. The molecular structure is stabilized by an O—H⋯N hydrogen bond and the crystal packing exhibits weak intermolecular C—H⋯O and π–π [centroid-to-centroid distances 3.663 (3)-4.073 (3) Å] interactions
4-[(E)-(4-Diethylamino-2-hydroxybenzylidene)amino]-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one
In the title compound, C22H26N4O2, the phenyl ring and hydroxybenzene group are twisted with respect to the central pyrazolone ring, making dihedral angles of 54.05 (5) and 21.80 (6)°, respectively. One of the ethyl groups is disordered over two positions with site occupancies of 0.872 (6) and 0.128 (6). The molecular structure features short intramolecular O—H⋯N and C—H⋯O contacts. The crystal packing exhibits weak intermolecular C—H⋯O and C—H⋯π interactions
2-Methyl-4,4-dioxo-N-phenyl-5,6-dihydro-1,4-oxathiine-3-carboxamide (Oxycarboxin)
In the title compound, C12H13NO4S, a systemic fungicide, the heterocycle adopts a lounge chair conformation and the dihedral angle between the ring planes is 25.8 (2)°. Intermolecular C—H⋯O hydrogen bonds are noted in the crystal structure. Also observed is a short interaction of a methylene hydrogen atom with the π-electron system of a phenyl ring in an adjacent molecule
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