2-Bromo-N′-[(Z)-2-bromo­benzyl­idene]-5-methoxy­benzohydrazide

In the title compound, C15H12Br2N2O2, the mol­ecule adopts an E conformation about the C=N double bond and a transoid conformation about the central N—N bond, with a C(=O)—N—N—C(H) dihedral angle of 169.4 (4)°. In the crystal, mol­ecules are linked by N—H⋯O hydrogen bonds, leading to C(4) chains. The packing also features slipped π–π stacking inter­actions, with a centroid–centroid separation of 3.838 (3) Å and a slippage of 1.19 Å

Ethyl 4-(3-bromo-2-thien­yl)-2-oxo-6-phenyl­cyclo­hex-3-ene-1-carboxyl­ate

The title compound, C19H17BrO3S, crystallizes with two mol­ecules in the asymmetric unit. The methyl group of one mol­ecule is disordered approximately equally over two positions. The dihedral angles between the thio­phene and phenyl groups are 68.5 (2) and 67.5 (2)° in the two mol­ecules

Non-Fermi liquid behavior in a fluctuating valence system, the filled skutterudite compound CeRu_{4}As_{12}

Electrical resistivity $\rho$, specific heat C, and magnetic susceptibility $\chi$ measurements made on the filled skutterudite CeRu_4As_{12} reveal non-Fermi liquid (NFL) T - dependences at low T, i.e., $\rho$(T) $\sim$ T^{1.4} and weak power law or logarithmic divergences in C(T)/T and $\chi$(T). Measurements also show that the T - dependence of the thermoelectric power S(T) deviates from that seen in other Ce systems. The NFL behavior appears to be associated with fluctuations of the Ce valence between 3^+ and 4^+ rather than a typical Kondo lattice scenario that would be appropriate for an integral Ce valence of 3^+.Comment: 18 pages, 5 figure

4-[4-(Heptyloxy)benzoyloxy]phenyl 2-oxo-7-trifluoromethyl-2 H

The title compound, C(31)H(27)F(3)O(7), is a liquid crystal and exhibits enanti­otropic SmA and nematic phase transitions. In the crystal, the the 2H-chromene ring system makes dihedral angles of 54.46 (17) and 7.79 (16)°, respectively, with the central benzene ring and 4-(hept­yloxy)benzene ring. The three F atoms of the –CF(3) group are disordered over two sets of sites, with an occupancy ratio of 0.62 (3):0.38 (3). The crystal structre features two pairs of C—H⋯O hydrogen bonds, which form inversion dimers and generate R (2) (2)(10) and R (2) (2)(30) ring patterns. C—H⋯O inter­actions along [100] and C—H⋯π inter­actions futher consolidate the packing, leading to a three-dimensional network

(2E)-3-(3-Bromo-4-meth­oxy­phen­yl)-1-(4-methyl­phen­yl)prop-2-en-1-one

The overall shape of the mol­ecule of the title compound, C17H15BrO2, can be described by the dihedral angles between three planar fragments: 1-bromo-2-meth­oxy­phenyl ring [maximum deviation = 0.003 (2) Å], the central prop-2-en-1-one chain [maximum deviation = 0.005 (2) Å], and the methyl­phenyl ring [maximum deviation = 0.004 (2) Å]. The terminal planes are twisted by 10.37 (12)°, while the central plane is almost coplanar with the methyl­phenyl ring [3.30 (13)°], but the dihedral angle with the other phenyl ring is significantly larger [8.76 (16)°]. In the crystal, mol­ecules are linked into chains along [001] by three C—H⋯O hydrogen bonds. These chains inter­act with each other by means of weak π–π contacts [centroid–centroid distances = 3.73 (1) and 3.44 (1) Å]. An inter­molecular C—H⋯Br inter­action also occurs

Th substituted SmFeAsO: structural details and superconductivity with Tc above 50 K

Superconducting poly- and single-crystalline samples of Sm1-xThxFeAsO with partial substitution of Sm3+ by Th4+ were synthesized and grown under high pressure and their structural, magnetic and transport properties are studied. The superconducting Tc reaches values higher than 50 K. Bulk superconducting samples (x = 0.08, 0.15, 0.3) do not show any signs of a phase transition from tetragonal to orthorhombic crystal structure at low temperatures. With Th substitution the unit cell parameters a and c shrink and the fractional atomic coordinate of the As site zAs remains almost unchanged, while that of Sm/Th zSm/Th increases. Upon warming from 5 K to 295 K the expansion of the FeAs layer thickness is dominant, while the changes in the other structural building blocks are smaller by a factor of 1/5, and they compensate each other, since the As-Sm/Th distance appears to contract by about the same amount as the O-Sm/Th expands. The poly- and single-crystalline samples are characterized by a full diamagnetic response in low magnetic field, by a high intergrain critical-current density for polycrystalline samples, and by a critical current density of the order of 8 x 105 A/cm2 for single crystals at 2 K in fields up to 7 T. The magnetic penetration depth anisotropy {\gamma}{\lambda} increases with decreasing temperature, a similar behavior to that of SmFeAsO1-xFy single crystals. The upper critical field estimated from resistance measurements is anisotropic with slopes of 5.4 T/K (H//ab plane) and 2.7 T/K (H//c axis), at temperatures sufficiently far below Tc. The upper critical field anisotropy {\gamma}H is in the range of 2, consistent with the tendency of a decreasing {\gamma}H with decreasing temperature, already reported for SmFeAsO1-xFy single crystals.Comment: 30 pages, 2 tables, 15 figure

Thermal Conversion of Guanylurea Dicyanamide into Graphitic Carbon Nitride via Prototype CNx Precursors

Guanylurea dicyanamide, [(H2N)C(-O)NHC(NH2)2][N(CN)2], has been synthesized by ion exchange reaction in aqueous solution and structurally characterized by single-crystal X-ray diffraction (C2/c, a = 2249.0(5) pm, b = 483.9(1) pm, c = 1382.4(3) pm, β = 99.49(3)°, V = 1483.8(5) × 106 pm3, T = 130 K). The thermal behavior of the molecular salt has been studied by thermal analysis, temperature-programmed X-ray powder diffraction, FTIR spectroscopy, and mass spectrometry between room temperature and 823 K. The results were interpreted on a molecular level in terms of a sequence of thermally induced addition, cyclization, and elimination reactions. As a consequence, melamine (2,4,6-triamino-1,3,5-triazine) is formed with concomitant loss of HNCO. Further condensation of melamine yields the prototypic CNx precursor melem (2,6,10-triamino-s-heptazine, C6N7(NH2)3), which alongside varying amounts of directly formed CNxHy material transforms into layered CNxHy phases without significant integration of oxygen into the core framework owing to the evaporation of HNCO. Thus, further evidence can be added to melamine and its condensation product melem acting as “key intermediates” in the synthetic pathway toward graphitic CNxHy materials, whose exact constitution is still a point at issue. Due to the characteristic formation process and hydrogen content a close relationship with the polymer melon is evident. In particular, the thermal transformation of guanylurea dicyanamide clearly demonstrates that the formation of volatile compounds such as HNCO during thermal decomposition may render a large variety of previously not considered molecular compounds suitable CNx precursors despite the presence of oxygen in the starting material

Giant crystal-electric-field effect and complex magnetic behavior in single-crystalline CeRh3Si2

Single-crystalline CeRh3Si2 was investigated by means of x-ray diffraction, magnetic susceptibility, magnetization, electrical resistivity, and specific heat measurements carried out in wide temperature and magnetic field ranges. Moreover, the electronic structure of the compound was studied at room temperature by cerium core-level x-ray photoemission spectroscopy (XPS). The physical properties were analyzed in terms of crystalline electric field and compared with results of ab-initio band structure calculations performed within the density functional theory approach. The compound was found to crystallize in the orthorhombic unit cell of the ErRh3Si2 type (space group Imma -- No.74, Pearson symbol: oI24) with the lattice parameters: a = 7.1330(14) A, b = 9.7340(19) A, and c = 5.6040(11) A. Analysis of the magnetic and XPS data revealed the presence of well localized magnetic moments of trivalent cerium ions. All physical properties were found to be highly anisotropic over the whole temperature range studied, and influenced by exceptionally strong crystalline electric field with the overall splitting of the 4f1 ground multiplet exceeding 5700 K. Antiferromagnetic order of the cerium magnetic moments at TN = 4.70(1)K and their subsequent spin rearrangement at Tt = 4.48(1) K manifest themselves as distinct anomalies in the temperature characteristics of all investigated physical properties and exhibit complex evolution in an external magnetic field. A tentative magnetic B-T phase diagram, constructed for B parallel to the b-axis being the easy magnetization direction, shows very complex magnetic behavior of CeRh3Si2, similar to that recently reported for an isostructural compound CeIr3Si2. The electronic band structure calculations corroborated the antiferromagnetic ordering of the cerium magnetic moments and well reproduced the experimental XPS valence band spectrum.Comment: 32 pages, 12 figures, to appear in Physical Review

Gabapentinium picrate

The title compound {systematic name: [1-(carboxy­meth­yl)cyclo­hexyl]methanaminium 2,4,6-trinitro­phenolate}, C9H18NO2 +·C6H2N3O7 −, was synthesized from picric acid and gabapentin. The crystal packing is stabilized by intra­molecular N—H⋯O=N and N—H⋯O—Ph hydrogen bonds. An O—H⋯O inter­action is also present