Synthesis of YbBr2 and YbCl2 and an x-ray diffraction study of the system YbBr2YbCl2

Ytterbium dichloride was prepared in pure form by the oxidation of elemental ytterbium by ZnCl₂ with subsequent removal of the zinc impurities by sublimation. Ytterbium dibromide in the orthorhombic SrI₂-type structural form was prepared in a sealed tantalum container by reduction of the tribromide with elemental ytterbium at a temperature not exceeding 960°C for 15 min. The dihalides, mixed intimately in appropriate molar ratios in a glove-box and contained in pyrolytic graphite boats, were melted under vacuum. These two halides form a solid solution with the SrI₂-type structure. Lattice parameters are reported as a function of composition.     

Synthesis and x-ray crystal structure of a stable α-chlorooxetane

The Barton modification of the Hunsdiecker reaction is the key step in the preparation of 3,5-anhydro-5R-chloro-1,2-O-isopropylidenexylofuranose (1), a stable α-chlorooxetane.     

Synthesis and x-ray structures of some homonuclear μ-alkylidenetungsten complexes

The complexes W₂{μ-CHCHC(CH₃)₂](CO)₁₀} and W₂{μ-CHCHC(CH₃)(CH₂)₃CH₃][(CO)₁₀} have been synthesized, and an X-ray diffraction study has revealed the presence of five CO groups on each metal center. The analogy between W₂{μ-CHCHC(CH₃)₂][(CO)₉]} anda complex of W(CO)₄ and a tungstabutadiene (CO)₅WCHCHC(CCH₃)₂ prompted the synthesis of the first heteroatom-substitued μ-alkylidene complexes of tungsten, starting from conjugated Fischer-typ carbene complexes (CO)₅WC(OR)CHCHR. The X-ray structure of the complex W₂{μ-C(OEt)CHCH(CH₃)][(CO)₉]} has also been determined. In the case of the simplest conjugated compelx (CO)₅WC(OR)CHCH₂, an interesting rearrangement initiated by addition of W(CO)₅ to the terminal CC double bond giving a dinuclear complex W(CO)₅[η²-CH₂CHC(OMe)W(CO)₅] in which the two metal centers are not directly linked, has been observed.     

Conformational investigation of α-methylthio and α-phenylthio derivatives of acetone and cyclohexanone by molecular mechanics. An x-ray study of α-phenylthioacetone

A conformational investigation of -methylthioacetone, -methylthiocyclohexanone, -phenylthioacetone, and -phenylthiocyclohexanone was undertaken in the MM2(87) force field. In all cases theac-G rotamers with unidirectional orientation of the C=O and S-R bonds are preferred in accordance with the experimental investigations. In all cases the energy of dipole-dipole interaction makes a contribution to the stabilization of these forms. For the eclipsedsp conformers the relatively high calculated values of the energies contradict the data of the experimental investigations, which take account of their participation in the equilibrium. X-ray crystallographic analysis of -phenylthioacetone (3) showed that thesp-T structure with a planar orientation of the thioanisole fragment is realized in the solid phase.A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan' Scientific Center, Russian Academy of Sciences, 420083 Kazan'. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1364–1371, June, 1992.     

High resolution photoemission and x-ray absorption spectroscopy of a lepidocrocite-like TiO2 nanosheet on Pt(110) (1 × 2)

The electronic structure of TiO(2) nanosheets on the Pt(110)-(1 × 2) surface has been investigated by using high resolution photoemission spectroscopy and x-ray absorption spectroscopy (XAS). The Ti 2p XAS spectra of the deposited TiO(2) films have been theoretically evaluated and, from the comparison with the experimental data, the assignment to a lepidocrocite-like structure is confirmed. Coexistence of TiO(2) islands with PtO(2) stripes for incomplete nanosheets is confirmed by high resolution photoemission data. The location of the valence and conduction band edges of the nanosheet has been experimentally determined allowing us to describe in details subtle electronic effects due to the interface with the substrate. The locations of the valence band maximum and the leading peak in the O 1s XAS spectrum indicate a band gap similar to anatase but with the Fermi level closer to mid-gap than found for bulk, n-type TiO(2).     

Analysis of x-ray Ni Kβ emission,xanes, xps,Ni 2p,and optical spectra of nickel(II) spinels and structure inference

X-ray absorption near-edge structure, X-ray Ni Kβ emission, X-ray photoelectron Ni 2p, and optical spectra are reported for NiM₂O₄ spinels (M = Al,Cr,Ga,Fe,Mn). The characteristic parameters of the Ni(II)-O chemical bond may be correlated with the structural properties (cation repartition and charge distribution).     

Synthesis and characterization of diblock copolymer of butadiene and 2-ethyl-2-oxazoline

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Preparation and x-ray structure analysis of [Rh2Cl2(μ-CO)(μ-vdpp)2] [vdpp=H2C=C(PPh2)2]

Summary The complex [Rh₂Cl₂(-CO)(-vdpp)₂] (1) (vdpp=H₂C=C(PPh₂)₂) was prepared by reaction of [Rh₂(CO)₄-(-Cl)₂] with vdpp. When (1) is allowed to stand overnight under an atmosphere of CO without stirringtrans-[Rh₂Cl₂(CO)₂(-vdpp)₂] is formed as a red precipitate in low yields. On rapid addition of CO the tricarbonyl complex [Rh₂(CO)₂(-CO)(-Cl)(-vdpp)₂]-Cl is formed instead. The chemical behaviour of the vdpp-substituted complex (1) is very similar to that of the corresponding dppm-substituted complex [Rh₂(Cl₂-(-CO)(-dppm)₂] (dppm=H₂C(PPh₂)₂). this similarity also extends to the molecular structures of both compounds. Unit cell parameters of (1): space group Pben (Z=8),a=2344.7(5),b=1506.9(7),c=3021.6(9)pm. Rh-Rh 267.4(1) pm.     

Collective dynamics of hydrated β-lactoglobulin by inelastic x-ray scattering

Inelastic x-ray scattering measurements of hydrated β-lactoglobulin (β-lg) were performed to investigate the collective dynamics of hydration water and hydrated protein on a picosecond time scale. Samples with different hydration levels h [=mass of water (g)/mass of protein (g)] of 0 (dry), 0.5, and 1.0 were measured at ambient temperature. The observed dynamical structure factor S(Q,ω)/S(Q) was analyzed by a model composed of a Lorentzian for the central peak and a damped harmonic oscillator (DHO) for the side peak. The dispersion relation between the excitation energy in the DHO model and the momentum transfer Q was obtained for the hydrated β-lg at both hydration levels, but no DHO excitation was found for the dry β-lg. The high-frequency sound velocity was similar to that previously observed in pure water. The ratio of the high-frequency sound velocity of hydrated β-lg to the adiabatic one of hydrated lysozyme (h=0.41) was estimated as ～1.6 for h=0.5. The value is significantly smaller than that (～2) of pure water that has the tetrahedral network structure. The present finding thus suggests that the tetrahedral network structure of water around the β-lg is partially disrupted by the perturbation from protein surface. These results are consistent with those reported from Brillouin neutron spectroscopy and molecular dynamics simulation studies of hydrated ribonuclease A.     

Structures and Vibrational Spectra of C_2 and LaC_2~ Clusters

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Structures and Stability of HNS_2 Isomers

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Structures and stabilities of HPS_2 isomers

The potential energy surface of HPS2 system containing nine isomers and fifteen transition states is obtained at MP2/6-311++G(d, p) and QCISD(t)/6-311++G(3df, 2p)(single-point) levels. On the potential energy surface, the lowest-lying frans-HSPS(EI) is found to be thermodynami-cally the most stable isomer followed by cis-HSPS(E2) and HP(S)S(C2v, E3) at 3.43 and 14.17 kJ/mol higher, respectively. The computed results show that species E1, E2, E3, stereo HP(S)S(Cs, E4) with PSS three-membered ring, isomers trans-HPSS(E5) and cis-HPSS(E6) which coexist with E4 are kinetically stable isomers. The products E6 and E5 in the reaction of HP with S2 can be isomerized into higher kinetic stable isomer E4 with 65.75 and 71.73 kJ/mol reaction barrier height, respectively. The predicated results may correct the possible inaccurate conclusion in that the product was experimentally assigned as isomer cis-HPSS(E6).     

Adsorption properties and photocatalytic activity of TiO2 and La-doped TiO2

Photocatalysts of TiO₂ and La-doped TiO₂ were prepared by calcining the pure TiO₂ sols and the sols mixed with La(NO₃)₃⋅6H₂O at 873 K, respectively. These photocatalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and N₂ adsorption-desorption isotherms measurement. As results, the BET surface area, pore diameter, mesopore volume and micropore volume slightly increased, while the crystallite size and the phase structure were little affected by lanthanum doping. The equilibrium adsorption of methylene blue (MB) on the photocatalysts were measured in a dark room. The adsorption isotherms were confirmed to fit to the Langmuir theory. Photocatalytic activities of the photocatalysts were studied by employing the photocatalytic degradation of MB in water and degradation of acetaldehyde in air under UV-irradiation using a black light. Kinetic analysis revealed that the rate controlling steps could be the surface reaction of the adsorbed MB on the catalyst surface for MB degradation and the reaction of adsorbed acetaldehyde with the gaseous acetaldehyde for degradation of acetaldehyde, respectively.     

A combined Mössbauer spectroscopy and x-ray diffraction operando study of Sn-based composite anode materials for Li-ion accumulators

The reaction mechanisms of Li with Sn/BPO₄ composites to be used as negative electrode materials for Li-ion batteries were studied during electrochemical cycling by operando Mössbauer spectroscopy and X-ray diffraction using a specifically conceived in situ electrochemical cell. The starting composites consist of three main components: β-Sn particles as the electrochemically active species, an inactive matrix of BPO₄ and an amorphous Sn^II-borophosphate interfacial phase linking the two former components and improving the cohesion of the composite. During the first discharge, the latter Sn(II) species are first reduced to zerovalent tin forming Li-poor Li–Sn alloys. After its complete reduction, the reaction of Li continues with β-Sn leading to Li–Sn alloys increasingly rich in Li, with a final composition between those of Li₇Sn₂ and Li₁₃Sn₅. X-ray diffraction shows a progressive loss of long range order of the composites with the suppression of the diffraction peaks of the initial β-Sn and the formation of an ill-defined mixture of Li–Sn alloys. The evolution of this mechanism is investigated on going from a reference Sn/BPO₄ composite prepared by conventional ceramic methods with common micrometric BPO₄ to a new improved material prepared by carbothermal synthesis starting from nanometric BPO₄. With the new composite prepared by carbothermal synthesis, a significant improvement of the reversible capacity at the first cycle is obtained together with a slight improvement of the cycling behaviour. An additional improvement can be obtained by increasing the rate of the first discharge, and thus hampering the formation of the thermodynamically stable LiSn intermetallic.     

Structures and stabilities of HPO_2 isomers

The potential energy surface of HPO2 system including eight isomers and twelve transition states is predicated at MP2/6-311++G(d, p) and QCISD(t)/6-311++G(3df,2p)(single-point) levels of theory. On the potential energy surface, cis-HOPO(E1) is found to be thermodynamically and kinetically most stable isomer followed by trans-HOPO(E2) and HPO(O)(C2v, E3) at 10.99 and 48.36 kJ/mol higher, respectively. Based on the potential energy surface, only E1 and E3 are thermodynamically stable isomers, and should be experimentally observable. The products cis-HPOO(E5) and frans-HPOO(E6) in the first-step reaction of HP with O2 can isomerize into isomer E1 that has higher stability. The reaction of OH with PO will directly lead to the formation of isomer E1. The computed results are well consistent with the previous experimental studies.     

Synthesis and Characterization of the Terpolymer of Itaconic Acid with Acrylamide and 2-Acrylamido-2-methylpropanesulfonic Acid

The thermal stability of the polymer is of great significance in paper, ceramics and oil industry1. Conventional polymers such as polyanionic cellulose can not meet high temperature limitations2-4. Aggour5-6 and Collette7 etc. have conducted extensive research on synthesis and characterizations of the copolymer or terpolymer containing 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS). Till now, very few research works have been reported on the terpolymer of itaconic acid (IA), acrylamid…     

Structures and Stability of NHS2 Isomers

Potential energy surface of HNS2 is investigated by means of second-order Moller-Plesset Perturbation theory(MP2) and QCISD(T) (single-point)methods,At final QCISD (T)/6-311 G(3df,2p)//MP2/6-311 G(d,p),level with zero-point vibrational energies included,cis-NHSS is found to be global minimum on the potential energy sufrace,followed by low-lying trans-HNSS ,HN(S)S(C2v).cis-HSNS,cis-NSSN,trans-HSNS,trans-NSSN,and HN(S)S(Cs) by 13.46,66.92,78.25,80.38,81.22,81.38 and 86.40 kJ/mol,respectively.A new high-lying HS(N)S isomer with Cs symmetry is located on the potential energy surface ,The kinetic stabilities of all isomers are predicted.Comprisons are made for HNS2 with its analogues,NHO2,HPS2 and HPO2,The causes that lead to the differences between HNS2 and its analogues are hypervalent capacity of phosphorus and distinct electronegativities of hydrogen,nitrogen and phosphorus.