Methyl­malon­amide and ethyl­malon­amide

In the title compounds, C₄H₈N₂O₂, (I), and C₅H₁₀N₂O₂, (II), respectively, the amide groups are rotated out of the central C—C—C plane by ca 76° in (I) and by 70–73° in (II). Compound (I) has crystallographic mirror symmetry perpendicular to the molecular plane.     

Di­methyl­phenyl­sulfonium tri­fluoro­methane­sulfonate and methyl­di­phenyl­sulfonium tri­fluoro­methane­sulfonate

The bonding geometry of sulfur in the cations of the title compounds, C₈H₁₁S⁺·CF₃SO₃^? and C₁₃H₁₃S⁺·CF₃SO₃^?, respectively, is similar and is independent of the ratio of the Me/Ph substituents. As expected, in both cations, the S—Ph bonds are somewhat shorter than the S—Me bonds. In both crystal structures, the interaction between cations and anions is similar.     

2,4,6‐Tri­chloro­phenyl­iso­nitrile and 2,4,6‐tri­chloro­benzo­nitrile

The molecular structures of the title compounds, 2,4,6‐tri­chloro­phenyl­iso­nitrile (IUPAC name: 2,4,6‐tri­chloro­phenyl isocyanide), C₇H₂Cl₃N, and 2,4,6‐tri­chloro­benzo­nitrile, C₇H₂Cl₃N, are normal. The two structures are not isomorphous, but do contain similar two‐dimensional layers in which pairs of mol­ecules are held together by pairs of Cl?CN [3.245 (3) Å] or Cl?NC [3.153 (2) Å] interactions. The two‐dimensional isomorphism is lost through different layer‐stacking modes.     

Heat capacities and absolute entropies of UTi<Subscript>2</Subscript>O<Subscript>6</Subscript> and CeTi<Subscript>2</Subscript>O<Subscript>6</Subscript>

Summary As part of a larger study of the physical properties of potential ceramic hosts for nuclear wastes, we report the molar heat capacity of brannerite (UTi₂O₆) and its cerium analog (CeTi₂O₆) from 10 to 400 K using an adiabatic calorimeter. At 298.15 K the standard molar heat capacities are (179.46±0.18) J K^-1 mol^-1 for UTi₂O₆ and (172.78±0.17) J K^-1 mol^-1 for CeTi₂O₆. Entropies were calculated from smooth fits of the experimental data and were found to be (175.56±0.35) J K^-1 mol^-1 and (171.63±0.34) J K^-1 mol^-1 for UTi₂O₆ and CeTi₂O₆, respectively. Using these entropies and enthalpy of formation data reported in the literature, Gibb’s free energies of formation from the elements and constituent oxides were calculated. Standard free energies of formation from the elements are (-2814.7±5.6) kJ mol^-1 for UTi₂O₆ and (-2786.3±5.6) kJ mol^-1 for CeTi₂O₆. The free energy of formation from the oxides at T=298.15 K are (-5.31±0.01) kJ mol^-1 and (15.88±0.03) kJ mol^-1 for UTi₂O₆ and CeTi₂O₆, respectively.     

Exo Diels–Alder adducts between ortho‐ and para‐N‐acetoxy­phenyl­male­imides and furan

In exo‐2‐(3,5‐dioxo‐10‐oxa‐4‐aza­tri­cyclo­[5.2.1.0^2,6]­dec‐8‐en‐4‐yl)­phenyl acetate, C₁₆H₁₃NO₅, the plane of the acetoxy group lies almost perpendicular to that of the phenyl ring [dihedral angle = 89.8 (1)°], in contrast with the smaller deviations found in the para isomer exo‐4‐(3,5‐dioxo‐10‐oxa‐4‐aza­tri­cyclo­[5.2.1.0^2,6]­dec‐8‐en‐4‐yl)­phenyl acetate, C₁₆H₁₃NO₅, these being 63.6 (1) and 37.0 (1)° for the two crystallographically independent mol­ecules. Irrespective of the position of the acetoxy group, both compounds pack through soft C—H⋯X (X is O or phenyl) interactions, forming interlinked centrosymmetric tetramers in the bc plane.     

Ethyl­tri­phenyl­phospho­nium perrhenate and (iodo­methyl)­tri­phenyl­phospho­nium perrhenate

Ethyl­tri­phenyl­phospho­nium perrhenate, (C₂₀H₂₀P)[ReO₄], and (iodo­methyl)­tri­phenyl­phospho­nium perrhenate, (C₁₉H₁₇IP)[ReO₄], have been crystallized from 2‐propanol. Both crystal structures consist of phospho­nium cations and perrhenate anions. The cations show the typical propeller‐like geometry. In both crystals, the positions of the nearly tetrahedral anions are stabilized by weak C—H⋯O hydrogen bonds, and for the latter compound, I⋯π interactions also occur.     

Structure and real composition of undoped and Cr- and Ni-doped Sr<Subscript>0.61</Subscript>Ba<Subscript>0.39</Subscript>Nb<Subscript>2</Subscript>O<Subscript>6</Subscript> single crystals

Strontium barium niobate crystals with congruent melting composition Sr_0.61Ba_0.39Nb₂O₆ (SBN-61), both nominally pure and doped with Cr³⁺ и Ni³⁺ ions, have been investigated by neutron diffraction. Different strontium and barium contents as well as their different distribution over the Sr1, of Sr2 and Ba2 crystallographic sites of SBN-61 structure, caused by introduction of dopants, have been revealed. Coordination polyhedra of cations have been established based on the analysis of cation–anion internuclear distances together with the calculation of bond-valence sums for cations, which are equal to their formal charge. It was found that the Nb1 and Nb2 atoms are located in distorted octahedra with quadfurcated (the Nb1O₆ polyhedron) or bifurcated (the Nb2O₆ polyhedron) vertices, and the Sr1 atoms are located in a cuboctahedron with bifurcated vertices in the base plane. Different polyhedra have been revealed for the Sr2 and Ba2 atoms: Sr2 atoms are coordinated by 15 oxygen atoms to form a highly distorted five-capped pentagonal prism, whereas Ba2 atoms are located in a highly distorted three-capped trigonal prism with a coordination number 9. Comparison of interatomic and internuclear distances, determined by X-ray and neutron diffraction analyses, respectively, allowed to reveal a highly pronounced shift of electron density in Nb1 and Sr2 polyhedra, responsible for the covalent bond and properties of crystals. Location of Cr³⁺ и Ni³⁺ dopant ions in the SBN-61 structure as well as their formal charges has been discussed.     

Polynuclear Ni<Superscript>II</Superscript> and Co<Superscript>II</Superscript> hexafluoroacetylacetonates

Hydrolysis of [M₄(hfac)₄(MeO)₄(MeOH)₄] (М = Сo, Ni and hfac is hexafluoroacetylaceton ate) is a convenient way of obtaining polynuclear complexes [Ni₇(hfac)₆(OH)₈(H₂O)₆]?2H₂O, [Co₁₂(hfac)₁₀(OH)₁₄(H₂O)₈]?2H₂O?2MePh, [Co₁₂(hfac)₁₀(OH)₁₄(H₂O)₄(Me₂CO)₄]?3PhMe, and [Co₁₂(hfac)₁₀(OH)₁₄(H₂O)₆(Me₂CO)₂]?2H₂O?2Me₂CO, whose structures were confirmed by X-ray analysis.     

High-temperature heat capacity and thermodynamic properties of Pb<Subscript>4</Subscript>V<Subscript>2</Subscript>O<Subscript>9</Subscript> and Pb<Subscript>8</Subscript>V<Subscript>2</Subscript>O<Subscript>13</Subscript>

The molar heat capacity of Pb₄V₂O₉ and Pb₈V₂O₁₃ in the temperature range 350–1000 K was measured by differential scanning calorimetry. It was determined that the plot C_p = f(T) for Pb₈V₂O₁₃ has an extremum within the range 416–516 K, which is due to a phase transition. A correlation was found between the heat capacity and composition of oxides in the PbO–V₂O₅ system. The data obtained allowed one to predict the specific heat capacity value for Pb(VO₃)₂.     

Interatomic interactions and electronic structure of NbSe<Subscript>2</Subscript> and Nb<Subscript>1.25</Subscript>Se<Subscript>2</Subscript> nanotubes

Atomic models of achiral NbSe₂ nanotubes are suggested. Band structure calculations have been performed to investigate the electronic structure and determine the parameters of interatomic interactions. The distribution of the density of states and pair bond occupancies of NbSe₂ nanotubes are analyzed in relation to the type of the atomic configuration and the tube diameter; the results are compared with the band structure of the 2H-NbSe₂ crystal. Calculations have been carried out on hypothetical superstoichiometric nanotubes with a formal composition Nb_1.25Se₂ as possible quasi-one-dimensional nanoforms of autointercalated niobium diselenide.Original Russian Text Copyright © 2004 by A. N. Enyashin, V. V. Ivanovskaya, I. R. Shein, Yu. N. Makurin, N. I. Medvedeva, A. A. Sofronov, and A. L. IvanovskiiTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 579–588, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Synthesis and Steric Structure of H-Leu-His-Lys-Leu-Gln-Thr-NH<Subscript>2</Subscript> and H-Ala-<Emphasis Type="Italic">D</Emphasis>-Ala-Lys-Leu-Ala-Thr-NH<Subscript>2</Subscript> Peptides

Conformational computations of the synthesized H-Leu-His-Lys-Leu-Gln-Thr-NH₂ and H-Ala-D-Ala-Lys-Leu-Ala-Thr-NH₂ peptide sequences corresponding to the 16–21 fragment of salmon calcitonin II and its highly active analog that exhibits an analgesic activity were performed. The molecular dynamics method with the AMBER force field was used to trace changes in the geometric parameters of the two molecules over the course of 1500 ps. The conformation of the molecular skeletons underwent no radical changes during computations, and relative flexibility was only revealed in the Lys³, Leu⁴, and Thr⁶ side chains.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 5, 2005, pp. 863–872.Original Russian Text Copyright © 2005 by Rogachevskii, Burov, Shchegolev.     

Development and Characterization of EST-SSR Markers from <em>Scapharca broughtonii</em> and Their Transferability in <em>Scapharca subcrenata</em> and <em>Tegillarca granosa</em>

Twenty-five novel EST-derived simple sequence repeat (EST-SSR) markers were developed in the ark shell Scapharca broughtonii. Polymorphisms of these EST-SSR markers were evaluated in 48 wild individuals collected from Shidao, Shandong Province, China. A total of 202 alleles were detected at 25 loci. The numbers of alleles per locus ranged from 4 to 14, with an average of 8.08. The observed and expected heterozygosities varied from 0.2917 to 1.000 and from 0.3570 to 0.9002, respectively. After sequential Bonferroni correction for multiple tests, only one locus was found to deviate from Hardy-Weinberg equilibrium. Twenty-five EST-SSR markers showed a high rate of across-species transferability (100%) in Scapharca subcrenata and a low rate of across-genus transferability (20%) in Tegillarca granosa. These EST-SSRs will be helpful for QTL mapping, molecular breeding and investigation of population genetic diversity in ark shell S. broughtonii and other Scapharca species.     

Dimethyl‐ and diethyl­dithio­cyanato­tin(IV)

The structures of dimethyl­dithio­cyanato­tin(IV), [Sn(CH₃)₂(NCS)₂], and diethyl­dithio­cyanato­tin(IV), [Sn(C₂H₅)₂(NCS)₂], have been determined. The dimethyl derivative has 2mm crystallographic symmetry and the diethyl derivative has twofold crystallographic symmetry. The experimental differences in the distances and angles around the Sn atom between the two structures agree reasonably well with the differences expected from the reaction path mapped previously [Britton & Dunitz (1981). J. Am. Chem. Soc. 103 , 2971–2979].     

Synthesis and characterization of Mn-, La-Mn- and La-Ca-Mn-citrates as precursors for LaMnO<Subscript>3</Subscript> and La<Subscript>1−x</Subscript>Ca<Subscript>x</Subscript>MnO<Subscript>3</Subscript>

Mn-, LaMn- and LaCaMn-citrates were synthesized at 60–120°C in ethylene glycol medium using chlorides or nitrates as metal sources. Their composition, IR spectra and thermal decomposition were studied. Equimolar La/Mn ratio has been established in the complex, prepared from chloride solution with the same initial composition of the metals. In the isolated three-metallic complex the molar ratio of the metals deviates from the composition in the initial solution. The final products of the heating of Mn- and mixed-metal LaMn-citrates at 1000°C are phase-homogeneous Mn₃O₄ (hausmannite) and LaMnO₃ respectively. Parasitic phase(s) are observed in La_xCa_1−xMn_yO₃, produced from LaCaMn-citrate.     

Separation and purification of <Superscript>249</Superscript>Cf and <Superscript>245</Superscript>Cm

There is a need to provide radioactivity standards of the higher actinides in support of both decommissioning and remediation activities as well as routine environmental analysis. In the case ²⁴⁹Cf, this will provide a useful calibration nuclide for both α-and γ-spectrometry as well as improving knowledge of the decay scheme for this nuclide. There is anecdotal evidence to suggest that the chemical yield of americium and curium may differ in radiochemical analysis. Thus, a chemical yield tracer of ²⁴⁵Cm may help to resolve this issue and will be suitable for both, suitable for use as a chemical yield tracer for both α-particle spectrometry and mass spectrometry. An aged source of ²⁴⁹Cf was used as the source material for the separation of these two nuclides by cation-exchange, using 2-hydroxy-2-methyl-propanoic acid at controlled pH as an eluant, ²⁴⁹Cf being eluted before the ²⁴⁵Cm daughter. The purity of both nuclides was measured by γ-ray spectrometry.     

o‐Chloro‐ and o‐bromo­benzonitrile: pseudosymmetry and pseudo‐isostructural packing

The structures of o‐chloro­benzonitrile, C₇H₄ClN, (I), and o‐bromo­benzonitrile, C₇H₄BrN, (II), have similar packing arrangements, even though Z′ = 4 in (I) and Z′ = 1 in (II). Both structures involve X⋯N inter­actions, as well as weak C—H⋯X and C—H⋯N hydrogen bonds. The four crystallographically independent mol­ecules in (I) are related by pseudosymmetry.     

2,4‐Di­nitro­phenyl­hydrazones of 2,4‐di­hydroxy­benz­aldehyde, 2,4‐di­hydroxy­aceto­phenone and 2,4‐di­hydroxy­benzo­phenone

In 2,4‐di­hydroxy­benz­aldehyde 2,4‐di­nitro­phenyl­hydrazone N,N‐di­methyl­form­amide solvate {or 4‐[(2,4‐di­nitro­phenyl)­hydrazono­methyl]­benzene‐1,3‐diol N,N‐di­methyl­form­amide solvate}, C₁₃H₁₀N₄O₆·C₃H₇NO, (X), 2,4‐di­hydroxy­aceto­phenone 2,4‐di­nitro­phenyl­hydrazone N,N‐di­methyl­form­am­ide solvate (or 4‐{1‐[(2,4‐di­nitro­phenyl)hydrazono]ethyl}benzene‐1,3‐diol N,N‐di­methyl­form­amide solvate), C₁₄H₁₂N₄O₆·C₃H₇NO, (XI), and 2,4‐di­hydroxy­benzo­phenone 2,4‐di­nitro­phenyl­hydrazone N,N‐di­methyl­acet­amide solvate (or 4‐­{[(2,4‐di­nitro­phenyl)hydrazono]phenyl­methyl}benzene‐1,3‐diol N,N‐di­methyl­acet­amide solvate), C₁₉H₁₄N₄O₆·C₄H₉NO, (XII), the molecules all lack a center of symmetry, crystallize in centrosymmetric space groups and have been observed to exhibit non‐linear optical activity. In each case, the hydrazone skeleton is fairly planar, facilitated by the presence of two intramolecular hydrogen bonds and some partial N—N double‐bond character. Each molecule is hydrogen bonded to one solvent mol­ecule.     

Identification and Determination of <em>Aconitum</em> Alkaloids in <em>Aconitum</em> Herbs and <em>Xiaohuoluo Pill</em> Using UPLC-ESI-MS

A rapid, specific, and sensitive ultra-performance liquid chromatography-electrospray ionization-mass spectrometry (UPLC-ESI-MS) method to examine the chemical differences between Aconitum herbs and processed products has been developed and validated. Combined with chemometrics analysis of principal component analysis (PCA) and orthogonal projection to latent structural discriminate analysis, diester-diterpenoid and monoester-type alkaloids, especially the five alkaloids which contributed to the chemical distinction between Aconitum herbs and processed products, namely mesaconitine (MA), aconitine (AC), hypaconitine (HA), benzoylmesaconitine (BMA), and benzoylhypaconitine (BHA), were picked out. Further, the five alkaloids and benzoylaconitine (BAC) have been simultaneously determined in the Xiaohuoluo pill. Chromatographic separations were achieved on a C₁₈ column and peaks were detected by mass spectrometry in positive ion mode and selected ion recording (SIR) mode. In quantitative analysis, the six alkaloids showed good regression, (r) > 0.9984, within the test ranges. The lower limit quantifications (LLOQs) for MA, AC, HA, BMA, BAC, and BHA were 1.41, 1.20, 1.92, 4.28, 1.99 and 2.02 ng·mL^-1, respectively. Recoveries ranged from 99.7% to 101.7%. The validated method was applied successfully in the analysis of the six alkaloids from different samples, in which significant variations were revealed. Results indicated that the developed assay can be used as an appropriate quality control assay for Xiaohuoluo pill and other herbal preparations containing Aconitum roots.     

Eu<Superscript>3+</Superscript>-doped LaPO<Subscript>4</Subscript> and LaAlO<Subscript>3</Subscript> nanosystems and their luminescence properties

Eu³⁺ ion-doped LaPO₄ nanowires or nanorods have been successfully synthesized by a simple hydrothermal method. The influence of varying the hydrothermal and subsequent sintering conditions on the morphology and structure of the LaPO₄ host has been investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). For comparison, the Eu³⁺ ions were also doped into monoclinic monazite LaPO₄ nanoparticles and perovskite LaAlO₃ nanoparticles. The relative intensities of the emission lines of the LaPO₄:Eu³⁺ nanosystems were essentially independent of their shape. The optimal doping concentrations in the monoclinic LaPO₄ and perovskite LaAlO₃ nanosystems were determined to be about 5.0 and 3.5 mol%, respectively. Under appropriate UV-radiation, the red light emitted from LaAlO₃:Eu³⁺ (3.5 mol%) was brighter than that from LaPO₄:Eu³⁺ (5.0 mol%) nanomaterial, resulting from differences in their spin-orbit couplings and covalence, which indicates that the nanoscale LaAlO₃ is a promising host material for rare earth ions. Electronic Supplementary Material  Supplementary material is available for this article at and is accessible for authorized users. Supported by the National Natural Science Foundation of China (Grant Nos. 20873039 & 90606001), Hunan Provincial Natural Science Foundation (No. 07jj4002), and the Students Innovation Training Fund of Hunan University