Configuration interaction calculations of satellite structure in photoelectron spectra of H2O

Configuration interaction wavefunctions were computed for the satellite peaks in the core and the valence photoelectron spectra of H₂O. Relative intensities were computed in the sudden approximation including electron correlation in the neutral ground state. The intensity profile of the O_1s ESCA spectrum is understood in terms of single excitations from the 3a₁ and the 1b₁ orbitals to low lying virtual MOs. Strong correlation effects are observed for the levels in the inner valence region where the satellites derive their intensity both from the 2a₁ and 3a₁ MOs.     

Thermal decomposition mechanisms of MgCl2·6H2O and MgCl2·H2O

The thermal decomposition mechanisms and the intermediate morphology of MgCl₂·6H₂O and MgCl₂·H₂O were studied using integrated thermal analysis, X-ray diffraction, scanning electron microscope and chemical analysis. The results showed that there were six steps in the thermal decomposition of MgCl₂·6H₂O: producing MgCl₂·4H₂O at 69 °C, MgCl₂·2H₂O at 129 °C, MgCl₂·nH₂O (1 ≤ n ≤ 2) and MgOHCl at 167 °C, the conversion of MgCl₂·nH₂O (1 ≤ n ≤ 2) to Mg(OH)Cl·0.3H₂O by simultaneous dehydration and hydrolysis at 203 °C, the dehydration of Mg(OH)Cl·0.3H₂O to MgOHCl at 235 °C, and finally the direct conversion of MgOHCl to the cylindrical particles of MgO at 415 °C. To restrain the sample hydrolysis and to obtain MgCl₂·H₂O, MgCl₂·6H₂O was first calcined in HCl atmosphere until 203 °C when MgCl₂·H₂O was obtained; HCl gas was then turned off and the calcination process continued, producing Mg₃Cl₂(OH)₄·2H₂O calcined at 203 °C, Mg₃(OH)₄Cl₂ at 220 °C and MgO at 360 °C. The temperature of producing MgO from calcination of MgCl₂·H₂O was lower (360 °C) than that from MgCl₂·6H₂O (415 °C) because of its more reactive intermediate products: the irregular shape and tiny needle-like Mg₃Cl₂(OH)₄·2H₂O particles and the uneven surface porous Mg₃(OH)₄Cl₂ particles. The MgO particles obtained at 360 °C had a flake structure.     

The crystal structure of hydrogen cerium(III) sulfate hydrate, [H3O][Ce(SO4)2] · H2O

[H₃O][Ce(SO₄)₂] · H₂O crystallizes in the monoclinic system with unit-cell dimensions (from single-crystal data) a = 9.359(4), b = 9.926(4), c = 8.444(3) Å, β = 96.53(9)° and space group P2₁/n, z = 4. The structure was solved by conventional heavy-atom methods using 1787 counter-measured reflections (MoKα radiation), and refined using full-matrix least-squares techniques to an R of 0.0465 (ωR = 0.0413). The structure consists of cerium(III) ions in irregular nine-coordination to oxygen atoms from two bidentate sulfate ions, four monodentate sulfate oxygen atoms, and one water molecule. The oxonium ions are present as isolated ions in the structure and take par in the hydrogen bonding network. The Ce-O bond lengths range from 2.454(7) to 2.626(6) Å.     

NMR study of water reorientation in molybdic acids: MoO3 · 2H2O and yellow MoO3 · H2O

Proton NMR relaxation times (T₂, T₁, T_1?) are reported for powder samples of MoO₃ · 2H₂O and yellow MoO₃ · H₂O in the temperature range 150–325 K and at 20 and 60 MHz. No translation of hydrogen atoms is detected but the spin-lattice relaxation behavior indicates reorientation of H₂O molecules. The waters coordinated to Mo atoms undergo 180° flips (about their C₂ axes) with similar motional parameters in both compounds. The interlayer waters in MoO₃ · 2H₂O undergo 180° flips with different parameters. An assumed Arrhenius-type temperature dependence of correlation times leads to preexponential factors which are “anomalously” low. The possible involvement of temperature-dependent activation barriers is discussed.     

Theoretical studies on the stability of the H3O radical based on ab initio UHF-CI calculations

An UHF-CI investigation of parts of the energy surface for the H₃O radical is reported. Several types of basis sets have been used and the CI expansion included all singly and doubly replaced configurations using an UHF determinant as the reference state. H₃O, constrained-to C_3v symmetry is in the best approximation found to be 20.5 kcal/mol less stable than H₂O + H. A small local barrier of 4.6 kcal/mol for dissociation is found on the UHF level of approximation. Correlation effects lower this barrier to 3.4 kcal/mol making the existence of a quasibound state with a measurable lifetime improbable. The height of the barrier was found to be very sensitive to the detailed form of the diffuse singly occupied orbital.     

Photoabsorption in H2O: Stieltjes-Tchebycheff calculations in the time-dependent Hartree-Fock approximation

Total and partial-channel photoabsorption cross-section calculations in H₂O are reported employing the time-dependent Hartree-Fock approximation and Stieltjes-Tchebycheff imaging procedures, and comparisons are made with the corresponding results of recent (e, 2e), (e, e + ion), and synchrotron-radiation dipole oscillator-strength studies.     

Synthesis and crystal structure of KNa3[Fe3O(CH3COO)6(H2O)2]3 [α-P2W17Fe(H2O)O61]·32.5H2O

A complex of the composition KNa₃[Fe₃O(CH₃COO)₆(H₂O)₃]₃ [α-P₂W₁₇Fe(H₂O)O₆₁]·32.5H₂O (I) was obtained by interaction of FeCl₃·6H₂O and phosphotungstate K₁₀[α₂-P₂W₁₇O₆₁]·20H₂O in an acetate buffer with a yield of 52%. Compound I was characterized by single crystal X-ray phase analysis and IR spectroscopy. In the crystal structure, the Na and K cations bind [Fe₃O(CH₃COO)₆(H₂O)₃]⁺ trinuclear cations and [α-P₂W₁₇Fe(H₂O)O₆₁]⁷⁻ heteropolytungstate anions into infinite zigzag chains. Original Russian Text Copyright ? 2005 by N. V. Izarova, M. N. Sokolov, A. V. Virovets, H. G. Platas, and V. P. Fedin __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 46, No. 1, pp. 149–155, January–February, 2005.     

Experimental and theoretical investigations on the electric field gradient at the Br site in Sr(BrO3)2 · H2O and Ba(BrO3)2 · H2O

Single-crystal Zeeman effect studies have been done using ⁷⁹Br NQR in Sr(BrO₃)₂ · H₂O and Ba(BrO₃)₂ · H₂O and the electric field gradient (EFG) parameters at the Br site have been determined. The point-charge model for the evaluation of EFG at the Br site, when applied to these systems, has not yielded satisfactory results. In another model, the total EFG is obtained as the sum of the covalent contribution and the inter-ionic contribution. To obtain the covalent contribution CNDO/2 MO calculations have been done for the (BrO₃)⁻ ions of these systems. There is excellent agreement with the experimental values in the case of Sr(BrO₃)₂ · H₂O, while the results on Ba(BrO₃)₂ · H₂O indicate that the structural data on this crystal need refinement.     

Na4H3[SiW9Al3(H2O)3O37]·12H2O/H2O: a new system for selective oxidation of alcohols with H2O2 as oxidant

This work describes a catalytic system consisting of both Na₄H₃[SiW₉Al₃(H₂O)₃O₃₇]·12H₂O(SiW₉Al₃) and water as solvents (a small quantity of organic solvents were used as co-solvent for a few substrates) that can be good for selective oxidation of alcohols to ketones (aldehydes) using 30% H₂O₂ without any phase-transfer catalyst under mild reaction conditions. The catalyst system allows easy product/catalyst separation. Under the given conditions, the secondary hydroxyl group was highly chemoselectively oxidized to the corresponding ketones in good yields in the presence of primary hydroxyl group within the same molecule, and hydroxides are selectively oxidized even in the presence of alkene. Benzylic alcohols were selectively oxidized to the corresponding benzaldehydes in good yields without over oxidation products in solvent-free conditions. Nitrogen, oxygen, sulfur-based moieties, at least for the cases where these atoms are not susceptible to oxidation, do not interfere with the catalytic alcohol oxidation.     

Hydrothermal synthesis, crystal structure and characterization of [Zn(H2O)4]2 [H2As6V15O42(H2O)]·2H2O

The compound [Zn(H₂O)₄]₂[H₂As₆V₁₅O₄₂(H₂O)]·2H₂O (1) has been synthesized and characterized by elemental analysis, IR, ESR, magnetic measurement, third-order nonlinear property study and single crystal X-ray diffraction analysis. The compound 1 crystallizes in trigonal space group R3, a=b=12.0601(17) Å, c=33.970(7) Å, γ=120°, V=4278.8(12) Å³, Z=3 and R1(wR2)=0.0512 (0.1171). The crystal structure is constructed from [H₂As₆V₁₅O₄₂(H₂O)]⁴⁻ anions and [Zn(H₂O)₄]²⁺ cations linked through hydrogen bonds into a network. The [H₂As₆V₁₅O₄₂(H₂O)]⁶⁻ cluster consists of 15 VO₅ square pyramids linked by three As₂O₅ handle-like units.     

Syntheses and structural determination of nine-coordinate K3[Nd(nta)2(H2O)]·6H2O and K3[Er(nta)2(H2O)]·5H2O

The syntheses and structural determination of Nd^III and Er^III complexes with nitrilotriacetic acid (nta) were reported in this paper. Their crystal and molecular structures and compositions were determined by single-crystal X-ray structure analyses and elemental analyses, respectively. The crystal of K₃[Nd^III(nta)₂(H₂O)]·6H₂O complex belongs to monoclinic crystal system and C2/c space group. The crystal data are as follows: a=1.5490(11) nm, b=1.3028(9) nm, c=2.6237(18) nm, β=96.803(10)°, V=5.257(6) nm³, Z=8, M=763.89, D_c=1.930 g cm⁻³, μ=2.535 mm⁻¹ and F(000)=3048. The final R₁ and wR₁ are 0.0390 and 0.0703 for 4501 (I>2σ(I)) unique reflections, R₂ and wR₂ are 0.0758 and 0.0783 for all 10474 reflections, respectively. The Nd^IIIN₂O₇ part in the [Nd^III(nta)₂(H₂O)]³⁻ complex anion has a pseudo-monocapped square antiprismatic nine-coordinate structure in which the eight coordinate atoms (two N and six O) are from the two nta ligands and a water molecule coordinate to the central Nd^III ion directly. The crystal of the K₃[Er^III(nta)₂(H₂O)]·5H₂O complex also belongs to monoclinic crystal system and C2/c space group. The crystal data are as follows: a=1.5343(5) nm, b=1.2880(4) nm, c=2.6154(8) nm, b=96.033(5)°, V=5.140(3) nm³, Z=8, M=768.89, D_c=1.987 g cm⁻³, μ=3.833 mm⁻¹ and F(000)=3032. The final R₁ and wR₁ are 0.0321 and 0.0671 for 4445 (I>2σ(I)) unique reflections, R₂ and wR₂ are 0.0432 and 0.0699 for all 10207 reflections, respectively. The Er^IIIN₂O₇ part in the [Er^III(nta)₂(H₂O)]³⁻ complex anion has the same structure as Nd^IIIN₂O₇ part in which the eight coordinate atoms (two N and six O) are from the two nta ligands and a water molecule coordinate to the central Nd^III ion directly.     

Nd(Gly)2Cl3·3H2O和Pr(Ala)3Cl3·3H2O的热力学性质

利用精密自动绝热热量计测定了Nd(Gly)₂Cl₃·3H₂O在80-357K和Pr(Ala)₃Cl₃·3H₂O在80-374K温区的热容. 根据两个化合物的热容计算出了相对于参考温度298.15K的热力学函数(H_T?H_298.15)和(S_T?S_298.15). 根据热重(TG)分析结果, 提出了这两个稀土化合物可能的热分解机理. 利用溶解-反应恒温热量计测定相关化合物的溶解焓并设计盖斯热化学循环, 计算出了两个化合物的标准摩尔生成焓.     

Solvent-assisted interaction between molecules: calculations at the Hartree-Fock + correlation level Part 1. The study of the BH3 + H2O and NH3 + NH3 systems

The dispersion interaction energy with the molecules BH₃ and NH₃ was computed using a specific supermolecule method. The essence of the approach used lies in applying a localized representation in the virtual space. This method makes it sensible to investigate the above systems surrounded by several water molecules.     

New process of preparation, structure, and physicochemical investigations of the new titanyl phosphate Ti2O(H2O)(PO4)2

New titanyl phosphate Ti₂O(H₂O)(PO₄)₂ has been prepared and characterized by X-ray and neutron diffraction, nuclear magnetic resonance, infrared and Raman spectroscopies and thermogravimetric analysis. The crystal structure has been solved from neutron powder diffraction data at 300 K by Rietveld method in P2₁ space group. The refinement led to satisfactory profile factors (R_p=2.7%, R_wp=3.2%) and crystal structure model indicators (R_B=5.8%, R_F=3.2%). The cell is monoclinic with a=7.3735 Å, b=7.0405 Å, c=7.6609 Å and β=121.48°, Z=4. The structure can be described as a three-dimensional framework built up by chains of [TiO₅(OH₂)] octahedra with alternative short bonds [Ti₍₁₎-O₍₁₂₎; Ti₍₂₎-O₍₁₂₎, 1.88-1.84 Å] and long ones [Ti₍₁₎-O_W; Ti₍₂₎-O_W, 2.25-2.23 Å] along c-axis and connected via [PO₄] tetrahedra. Oxygen atom denoted O₍₁₂₎ is only linked to two titanium atoms and Oxygen atom denoted O_W is linked to two titanium atoms and two hydrogen atoms. O₍₁₂₎ and O_W are not linked to P atoms and justify the titanyl phosphate formulation Ti₂O(H₂O)(PO₄)₂. The infrared and Raman spectra presents peaks due to vibrations of Ti-O, P-O and O-H bonds. The ³¹P MAS NMR spectrum reveals two ³¹P resonance lines, in agreement with the structure which showed two crystallographic sites for phosphorus. The thermogravimetric analysis show that Ti₂O(H₂O)(PO₄)₂ is thermally stable until 400 °C. Above this temperature, it losses water and decomposes to Ti₅O₄(PO₄)₄ and TiP₂O₇.     

Syntheses and structures of three new scandium selenites: Sc2(SeO3)3·H2O, Sc2 (SeO3)3·3H2O and CsSc3(SeO3)4 (HSeO3)2·2H2O

Three new hydrated scandium selenites have been hydrothermally synthesized as single crystals and structurally and physically characterized. Sc₂(SeO₃)₃·H₂O crystallizes as a new structure type containing novel ScO₇ pentagonal bipyramidal and ScO₆₊₁ capped octahedral coordination polyhedra. Sc₂(SeO₃)₃·3H₂O contains typical ScO₆ octahedra and is isostructural with its M₂(SeO₃)₃·3H₂O (M=Al, Cr, Fe, Ga) congeners. CsSc₃(SeO₃)₄(HSeO₃)₂·2H₂O contains near-regular ScO₆ octahedra and has essentially the same structure as its indium-containing analogue. All three phases contain the expected pyramidal [SeO₃]^2- selenite groups. Crystal data: Sc₂(SeO₃)₃·3H₂O, M_r=524.85, trigonal, R3c (No. 161), , , , Z=6, R(F)=0.018, wR(F²)=0.036; Sc₂(SeO₃)₃·H₂O, M_r=488.82, orthorhombic, P2₁2₁2₁ (No. 19), , , , , Z=4, R(F)=0.051, wR(F²)=0.086; CsSc₃(SeO₃)₄(HSeO₃)₂·2H₂O, M_r=1067.60, orthorhombic, Pnma (No. 62), , , , , Z=4, R(F)=0.035, wR(F²)=0.070.     

Hydrothermal synthesis and structure characterization of a new 3D vanadium hydrogen phosphite with 14-ring channels: (C5N2H14)[VO(H2O)]3(HPO3)4·H2O

A new 3D vanadium hydrogen phosphite, (C₅N₂H₁₄)[VO(H₂O)]₃(HPO₃)₄·H₂O, has been prepared by hydrothermal reactions and characterized by single crystal X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, and magnetic techniques. It crystallizes in the triclinic space group P-1 (no. 2) with , , , α=76.124(3)°, β=83.726(4)^o, γ=75.222(4)^o, Z=2. The structure is built up from sharing equatorial oxygen atoms of VO₅(H₂O) octahedra with HPO₃ tetrahedra, which can be viewed as a (3,4) connected net. The framework is mainly constructed by two types of four-ring related chains. Intrachain and interchain hydrogen bonds play an important role on supporting the framework structure. The 14-ring tunnels in the structure are filled with 1-methypiperazinium and water molecules, which also contribute the hydrogen bonding with the vanadium phosphite framework.     

Infrared spectra of (CH3)2O and (CH3)2O + H2O at low temperature

Fourier transform infrared reflection spectroscopy (incidence angle of 5°) was used to characterize thin films of dimethyl ether (DME) and of mixtures containing water and DME between 10 and 160 K under a pressure of 10⁻⁷ mbar. Solid DME has two solid phases: an amorphous phase which is obtained below 65 K and a crystalline phase >65 K. From 90 K, DME begins to sublimate with surface binding energy of 20±2 kJ mol⁻¹. Vibrational spectrum of DME trapped in water ice remains nearly unchanged from 30 to 120 K. Between 120 and 130 K, a large part of DME is released and strong changes in the frequencies and the profile of the absorptions of DME are observed. This behavior suggests the formation of clathrate hydrate. Below 120 K, the trapped DME is hydrogen-bonded to water molecules.