Raman analysis of mode softening in nanoparticle CeO(2-δ) and Au-CeO(2-δ) during CO oxidation

Oxygen vacancy levels are monitored during the oxidation of CO by CeO(2-δ) nanorods and Au-CeO(2-δ) nanorods, nanocubes, and nanopolyhedra by using Raman scattering. The first-order CeO(2) F(2g) peak near 460 cm(-1) decreases when this reaction is fast (fast reduction and relatively slow reoxidation of the surface), because of the lattice expansion that occurs when Ce(3+) replaces Ce(4+) during oxygen vacancy creation. This shift correlates with reactivity for CO oxidation. Increases in the oxygen deficit δ as large as ~0.04 are measured relative to conditions when the ceria is not reduced.     

Structure and chemical behavior of (+)-δ-cadinol

The review summarizes data on natural sources, the history of the structure determination, and transformations of the rare sesquiterpenoid (+)-δ-cadinol.     

Synthesis and Crystal Structure of 1-(N,N-Di-(p-toluenesulfonyl))-amino-2-(N'-p-toluenesulfonyl)-amino-3,5-dinitrobenzene

The title compound,1-(N,N-di-(p-toluenesulfonyl))-amino-2-(N'-p-toluenesulfonyl)-amino-3,5-dinitrobenzene,was synthesized and structurally determined by single-crystal X-ray diffraction method. It crystallizes in orthorhombic,space group Pna21 with a=13.723(2),b=25.354(4),c=8.6565(12) ,V=3011.9(8) 3,Z=4,Mr=660.68,F(000)=1368,Dc=1.457 g/cm3,μ=0.309,the final R=0.0609 and wR=0.1042. The H atom of N2-H group,which is the unique recognition site to anion,is enveloped by two oxygen atoms and one benzene from two and one p-toluenesulfonyl moieties,respectively.     

Structure and potential energy surface of K+·CX2

The potential energy surface of K⁺·CO₂ and K⁺·CS₂ complexes are determined at high levels of ab initio theory (CCSD), B3LYP, and MP2 using different basis sets. These calculations predict the existence of three minima for K⁺·CO₂ complex; linear, quadrilateral and Y-shape, and two minima for K⁺·CS₂ complex; bent and Y-shape. In addition, the binding energies, and other thermodynamic quantities are calculated at different levels of theories. Our calculations show that the difference in the global minima geometries of both complexes is mainly due to the sign of the quadrupole moment of CO₂ and CS₂ molecules.     

Structure and conductivity in CeNb3O9-δ

Abstract  

In the search of new materials for solid oxide fuel cells, a study of the structure and electrical conductivity of Mg-doped and nominally pure CeNb₃O_9-δ was undertaken. This material exhibits an orthorhombic crystal structure as determined by Rietveld refinement. Through a combined study of 4-point DC and AC impedance spectroscopy, it was determined that the material presents oxygen ion conductivity, electron conductivity and electron-hole conductivity according to the partial pressure of oxygen and temperature in agreement with a simple defect chemistry model. Finally, some experiments seem to indicate the presence of proton conduction.     

Highly crystalline strontium ferrites SrFeO(3-δ): an easy and effective wet-chemistry synthesis

The synthesis of strontium ferrite SrFeO(3-δ) has been explored through wet-chemistry methods in order to optimize a quick, easy and reproducible method to obtain the perovskite in pure crystalline form with a high yield. Among the three investigated synthetic paths, (i) coprecipitation of hydroxides, (ii) coprecipitation of oxalates and (iii) polyol-assisted coprecipitation, only the second one was effective in obtaining the desired perovskite modification as a single phase. The products were analyzed by means of powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), to determine the crystalline structure and the chemical composition of the sample surface, respectively, and to optimise the synthetic process. Pure samples were further characterised by means of inductively coupled plasma (ICP-AES) analysis, nitrogen adsorption, elemental analysis, temperature programmed reduction (TPR) and M?ssbauer spectroscopy.     

Structure and properties of Ni(110) surface coadsorbing chlorine and oxygen

The coadsorption of chlorine with oxygen on Ni(110) surface has been investigated by XPS, UPS, AES and work function measurements. The chlorine preadsorption drastically inhibits the further uptake of oxygen. On the contrary, precovered oxygen has hardly any influence on the additional adsorption of chlorine due to the incorporation of precovered oxygen into the subsurface driven by the chlorine coadsorption. ARXPS measurements provide the evidence for this coadsorption model. The thermal desorption of chlorine and oxygen from the coadsorption surface is very similar to that of both individual adsorbates under the same heating conditions, but the desorption temperature of both the adsorbates apparently decreases on the coadsorption surface. The coadsorption and thermodesorption mechanisms are also discussed in detail.     

Structure and stability of one-dimensional o-phthalaldehyde lines on the Si(100)-2 × 1:H surface

We present the structural models for the o-phthalaldehyde (OP) molecular lines on the H-terminated Si(100) surface which were recently observed by scanning tunnelling microscopy. Our first-principles density-functional theory calculations show that the formation of OP lines is not only kinetically more facile but also thermodynamically more stable than those of previously reported alkene lines.     

The synergy of modulated surface polarity and oxygen vacancy for CO2 to methanol over Zn(δ-)-Ti(δ+)Ovacancy

Bi-functional catalysts,which can be traced back to 1960s,are widely applied in energy conversion and chemical transformation[1].Generally,the enhanced performance of the bi-functional catalyst comes from the local geometry or electron density change after the second component introduced.These changes facilitate the reaction at the structure or electron density level[2].In fact,it is a great challenge to understand and control those effects[3].     

Water vapour adsorption and contrast-modified SAXS in microporous polymer-based carbons of different surface chemistry

The adsorption of water vapour on highly microporous activated carbons with different surface chemistry is investigated by small angle X-ray scattering (SAXS) as well as by adsorption isotherms. The water changes the intensity of the SAXS in a way that depends on how the pores are filled. With wetting liquids such as hexane, a pseudo binary model can be assumed in which pore-filling in reciprocal space q is described by a density function p(q). For water, clusters develop, even in the most oxidized carbon, creating a fully ternary system. In the Porod scattering region, however, the final slope is insensitive to the liquid-vapour interfaces. In this region, for the less oxidized samples, p(q) shows reasonable agreement with the adsorption isotherms. At low relative pressure P/P ₀, however, the SAXS results indicate a small degree of filling (about 10%) that is not reflected in the isotherms. The highly oxidized sample attains a degree of filling of about 70% that, unlike the corresponding isotherm, is constant for P/P ₀>0. These differences may be due to kinetic effects and/or ageing, involving either redistribution of the water molecules or modifications of the surface groups.     

Formation of μ(2)-hydroxo-bonded (MgPc)2OH- assemblies and (C60(-))2 dimers in ionic fullerene {(MgPc)2OH-}2·(C60(-))2·(cation+)4 complexes

Ionic complexes containing μ(2)-hydroxo-bonded (MgPc)(2)OH(-) phthalocyanine assemblies and C(60)(-) anions: {(MgPc)(2)OH(-)}(2)·(C(60)(-))(2)·(PMDAE(+))(4)·(C(6)H(5)CN)(4) (1); {(MgPc)(2)OH(-)}(2)·(C(60)(-))(2)·(TMP(+))(4)·(C(6)H(5)CN)(3)·(C(6)H(4)Cl(2))(2.5) (2) (where PMDAE(+) is the cation of N,N,N',N',N'-pentamethyldiaminoethane and TMP(+) is the N,N'N'-trimethylpiperazinium cation) have been obtained as single crystals. The ionic ground state of the complexes is justified by the EPR spectra and the spectra in the IR and NIR ranges. The C(60)˙(-) radical anions are dimerized both in 1 and 2 in the 240-220 K range. Dimerization is accompanied by the reversible transition of the complexes from paramagnetic to diamagnetic state. MgPc forms unusual (MgPc)(2)OH(-) assemblies, in which the hydroxo-anion coordinates to two MgPc molecules by a μ(2)-fashion. The length of the Mg-O bonds is 1.936-1.955(2) ?, the Mg-O-Mg angle is 133.37-135.27(4)° and the displacement of the Mg atoms out of the mean 24-atom phthalocyanine plane is 0.77-0.86 ?. The packing of spherical fullerene and planar phthalocyanine molecules is attained in a crystal by the insertion of fullerenes between phenylene groups of phthalocyanines. It has been shown that metal phthalocyanines in ionic complexes with C(60) form M(II)Pc·(L(-)) assemblies, whereas metalloporphyrins form M(II)porphyrin·(C(+)) assemblies.     

Crystal and Molecular Structure of Hexahydro-2-(Nitro-Benzoylmethylene)Pyrimidine

1INTRODUCTIONHeterocyclicketeneaminalsareversatilestartingmaterialsforthesynthesisofawidevarietyofnewheterocyclesandfusedheterocycles.Thus,thesynthesisandre-actionofheterocyclicketeneaminalshavegivenrisetomuchattention[18i.Recentlynitrationofheterocyclicketeneaminalswasstudied[9i.Wehavepreparedhexahydro-2-(nitro-benzoylmethylene)pyrimidi(1).ItscrystalstructurehasbeendeterminedbyX-raydiffractionmethodandthemolecularstructureisdiscussed.2EXPERIMENTALThesinglecrystalofhexahydro-2-(nitr…     

Synthesis and Crystal Structure of 5-N-i-Propyl-2-(2′-nitrobenzenesulfonyl)-glutamine

IntroductionAcetohydroxy acid synthase(AHAS) is a perfecttarget for the design of environmentally benign herbi-cides because it is a key enzyme that is absent in ani-mals but is important for the biosynthesis of branched-chain amino acids in plants[1,2]. …     

Synthesis and Crystal Structure of 1-(o-methylphenyl)-2-(p-methoxyphenyl)-1,3,2-diazaphospholidin-4-thione-2-sulfide

11NTRODUCTIoNThederivativesofdiazaphospholidinoneorthecorrespondingthionesareknowntopossessinterestingbiologicalproperties,suchasherbicidalactivity"'2i.Inrecentyears,itwasreportedthatthel,4,2-diazaphospholindine-5-thione-2havegoodselectiveherbicidalactivity"'41.Tolookformoreeffectiveherbicideswithlowtoxicity,aseriesofnovel1-(o-methylphenyl)-2-(p-methoxyphenyl)-phospholidin-4-thione-sulfideshavebeensynthesizedandtheirmolecularstructuresstudied.PreliminarybioassaysshowthatthesecomPoundshaveg…     

Textural and surface chemistry of activated bagasse and its role in the removal of chromium ions from solution

The role of the surface chemical and physical properties of activated carbon in the removal of chromium was investigated. This was conducted by fitting the chromium removal by adsorption and reduction to Cr(III) to the physical properties including total surface and pore size of the carbon and its chemical property globally measured using carbon pH. The role of heteroatoms—sulfur, nitrogen, hydrogen and oxygen, to chromium removal was also investigated. This study showed that the structural and chemical properties displayed dual and conflicting properties in removing chromium. As such efficiencies gained in controlling the structure of the carbon are minimal. Optimal carbon properties which exhibited high chromium adsorption included high surface area, large pore size, high quantities of sulfur and nitrogen and minimal hydrogen and oxygen contents.     

Structure of 1-β-d-xylofuranosyluracil in the crystal and in solution

The molecular and crystal structure of 1-β-d-xylofuranosyluracil hydrate was established by X-ray diffraction analysis. The mutual arrangement of the xylofuranose fragment and the nucleic base corresponds to the anti conformation. The furanose ring adopts a C-envelope conformation. The structure of the nucleoside in a DMSO-d₆ solution has been determined by¹H NMR spectroscopy. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1378–1380, July, 1998.     

Synthesis,Characterization and X-ray Structure of N-(4-bromobutanoyl-N’-(2-3- and 4-methylphenyl)thiourea

N-4-(bromobutanoyl)-N'-(o-, m- and p-tolyl)thioureas 3a, 3b and 3c respectively, were synthesized by the reaction of 4-bromobutanoylisothiocyanate with p-, m- and o-toludine. The products were characterized by IR, and NMR spectroscopic techniques. The two carbonoylthiourea isomers N-(4-bromobutanoyl)-N'-(3-methylphenyl)thiourea(3b) and N-(4-bromobutanoyl)-N'-(4-methylphenyl)thiourea(3c) were obtained in crystalline form by recrystallization from DMSO. Xray crystallographic studies showed that both compounds 3b and 3c crystallize in triclinic system with space group of P1. The molecules adopt trans-cis configuration with respect to the positions of 4-bromobutanoyl and tolyl groups respectively, against the thiono C=S bond across their C–N bonds. The configuration is attributed by the intrahydrogen bond between the carbonyl oxygen and amide hydrogen atoms. Both crystal structures are stabilized by N–H···S intermolecular hydrogen bonds to form dimers and arranged along the b axis.     

Crystal Structure of 2-(4-Fluorophenylamino)-2-thiomethyl acetophenone

1mThODUCTIONThioacetalshavebeenwellstudied,becauseoftheirapplicationsinorganicsyn-thesist1i.However,aketohemithioacetalshaveseldombeeninvestigated.Inthispa-Per,wediscussedthecrystalstructureofthetitlecompoundsynthesizedbythereac-tionofabenzoylhemithioacetal(2-hydroxy-2-thiomethylacetoPhenone)and4-fluthroaniline.Sinceknowledgeofthemolecularandcrystalstructureofthetitlecom-PoundwasconsideredusefulforunderstandingthemechanismofthereactionandchemicalproPertiesofaketohemithioacetal,theX-raycr…     

Structure of (O→Si)-(acetoxymethyl)trifluorosilane in three phase states and in solutions

According to the IR spectroscopy data, the molecules of (O→Si)-(acetoxymethyl)trifluorosilane having in the liquid state and in polar media the intramolecular bond C=O→Si, exist in the gas phase in the temperature range 438–538 K in the equilibrium with the molecules with tetracoordinate silicon atom. This allowed to determine experimentally the enthalpy of formation of the intramolecular bond C=O→Si for the gas phase to be ΔH = 2.2±0.1 kcal mol⁻¹. In the solid state at 110 K and in the CS₂ solution, along with molecule with the C=O→Si bond, the dimers exist, which include both tetra- and pentacoordinate silicon atom. The data of quantum-chemical calculations (B3LYP/6-311G**) show that the shortest intermolecular bond Si-F→Si is realized in the associate formed by the molecules in the ap,sp- and sp,sp-forms, and the longest one, when both components are in the sp,sp-forms.     

Structure of clean and hydrated α-Al2O3 (1102) surfaces: implication on surface charge

Periodic DFT calculations coupled to a first-principle thermodynamic approach have allowed us to establish a surface phase diagram for the different terminations of the α-Al(2)O(3) (1102) surface in various temperature and water pressure conditions. Theoretical results are compared with previous experimental data from the literature. Under a wide range of temperature and water pressure (including ambient conditions) the most stable surface (denoted C2_1H(2)O in this work) is terminated with singly coordinated hydroxyls on four-fold coordinated aluminium (Al(4C)-μ(1)-OH) while most existing surface models are only considering six-fold coordinated surface Al atoms as in the bulk structure of alumina. The presence of more acidic Al(4C)-μ(1)-OH sites helps explain the low Point of Zero Charge (PZC) (between 5 and 6) determined from the onset of Mo oxoanions adsorption on (1102) single crystal wafers. It is also postulated that another termination (corresponding to the hydration of the non-polar, stoichiometric surface, stable in dehydrated conditions) may be observed in aqueous solution depending on the surface preparation conditions.