Systems R-Fe-O (R=Ho, Er): Thermodynamic properties of ternary oxides using differential scanning calorimetry and solid-state electrochemical cells

The thermodynamic properties of three different types of ternary oxides RFeO₃(s), R₃Fe₅O₁₂(s) and RFe₂O₄(s) (where R=Ho and Er) have been determined by calorimetric and solid-state galvanic cell methods. Heat capacities of RFeO₃(s) and R₃Fe₅O₁₂(s) have been determined by differential scanning calorimetry from 130 to 860 K. Heat capacity measurements from 130 to 860 K revealed λ-type anomalies for RFeO₃(s) and R₃Fe₅O₁₂(s) compounds which are assigned due to magnetic order-disorder transitions. The oxygen chemical potentials corresponding to the three-phase equilibria involving these ternary oxides have been determined by using solid-state electrochemical cells. The standard molar Gibbs energies of formation of RFeO₃(s), R₃Fe₅O₁₂(s) and RFe₂O₄(s) have been computed from the oxygen potential data. Based on the thermodynamic information, oxygen potential diagrams have been computed for the systems R-Fe-O (R=Ho and Er) at two different temperatures: T=1250 and 1450 K. Thermodynamic functions like , , H^o, G^o, , , , , and have been generated for the compounds RFeO₃(s) and R₃Fe₅O₁₂(s) based on the experimental data obtained in this study and the available data in the literature.     

Three-dimensional molecular network, [{Cu(dps)2(SO4)}·3H2O·DMF]n, and its different third-order NLO performance (dps=4,4′-dipyridyl sulfide)

A new three-dimensional non-interpenetrating coordination polymer, [{Cu(dps)₂(SO₄)}·3H₂O·DMF]_n (1) (dps=4,4′-dipyridyl sulfide) was synthesized and structurally characterized. 1 crystallizes in triclinic system, space group P−1 with cell parameters of a=10.9412(1) Å, b=11.8999(1) Å, c=12.5057(1) Å, V=1400.7(3) Å³, Z=2, D_c=1.573 g cm⁻³, F(0 0 0)=686, μ=1.059 mm⁻¹. R₁=0.0436, wR₂=0.1148. In the polymeric architecture, serve as bridging coligands to connect highly puckered [Cu₂(dps)₂]_n frameworks resulting in a 3D motif containing channels for guest molecule inclusion. Quantum chemistry calculation shows that the third-order NLO properties of polymer 1 are controlled by groups and dps ligands, and metal ions have less influence on the third-order NLO properties.     

Synthesis and single crystal structures of ternary phosphides Li4SrP2 and AAeP (A=Li, Na; Ae=Sr, Ba)

Two new (NaSrP, Li₄SrP₂) and two known (LiSrP, LiBaP) ternary phosphides have been synthesized and characterized using single crystal X-ray diffraction studies. NaSrP crystallizes in the non-centrosymmetric hexagonal space group (#189, a=7.6357(3) Å, c=4.4698(3) Å, V=225.69(2) Å³, Z=3, and R/wR=0.0173/0.0268). NaSrP adopts an ordered Fe₂P structure type. PSr₆ trigonal prisms share trigonal (pinacoid) faces to form 1D chains. Those chains define large channels along the [001] direction through edge-sharing. The channels are filled by chains of PNa₆ face-sharing trigonal prisms. Li₄SrP₂ crystallizes in the rhombohedral space group (#166, a=4.2813(2) Å, c=23.437(2) Å, V=372.04(4) Å³, Z=3, and R/wR=0.0142/0.0222). In contrast to previous reports, LiSrP and LiBaP crystallize in the centrosymmetric hexagonal space group P6₃/mmc (#194, a=4.3674(3) Å, c=7.9802(11) Å, V=131.82(2) Å³, Z=2, and R/wR=0.0099/0.0217 for LiSrP; a=4.5003(2) Å, c=8.6049(7) Å, V=150.92(2) Å³, Z=2, and R/wR=0.0098/0.0210 for LiBaP). Li₄SrP₂, LiSrP, and LiBaP can be described as Li₃P derivatives. Li atoms and P atoms make a graphite-like hexagonal layer, . In LiSrP and LiBaP, Sr or Ba atoms reside between layers to substitute for two Li atoms of Li₃P, while in Li₄SrP₂, Sr substitutes only between every other layer.     

The steric effect of o-tolyl ligand on the fluxionality behavior of some binuclear organoplatinum(II) complexes with bis(diphenylphosphino)methane as bridging ligand

A series of binuclear organoplatinum(II) complexes of general formula cis,cis-[R₂Pt(μ-SMe₂)(μ-dppm)Pt(o-MeC₆H₄)₂], 3a-3d, in which R = Ph, p-MeC₆H₄, m-MeC₆H₄ or p-MeOC₆H₄, were prepared by the reaction of monomeric precursors [Pt(o-MeC₆H₄)₂(dppm)] and cis-[PtR₂(SMe₂)₂]. The binuclear dialkyl analogs, in which R = Me (3e) or R₂ = {(CH₂)₄} (3f), were prepared by the reaction of cis-[Pt(o-MeC₆H₄)₂ (SMe₂)₂] and [PtR₂ (dppm)]. The complexes were fully characterized by multinuclear (¹H, ¹³C, ³¹P, ¹⁹⁵Pt) NMR spectroscopy each as a mixture of syn and anti isomers (depending on the relative orientations of Me substituents on o-tolyl ligands) and each isomer was shown to have a rigid structure. Other binuclear analogs , 3g-3j, in which R is a less steric demanding aryl groups m-MeC₆H₄ or p-MeOC₆H₄, and R′ = Me or , were prepared by the reaction of cis-[PtR₂(SMe₂)₂] and , and shown to have fluxional structures.     

Heat capacities, order-disorder transitions, and thermodynamic properties of rare-earth orthoferrites and rare-earth iron garnets

Rare-earth orthoferrites, RFeO₃, and rare-earth iron garnets (RIGs) R₃Fe₅O₁₂ (R=rare-earth elements) were prepared by citrate-nitrate gel combustion method and characterized by X-ray diffraction method. Isobaric molar heat capacities of these oxides were determined by using differential scanning calorimetry from 130 to 860 K. Order-disorder transition temperatures were determined from the heat capacity measurements. The Néel temperatures (T_N) due to antiferromagentic to paramagnetic transitions in orthoferrites and the Curie temperatures (T_C) due to ferrimagnetic to paramagnetic transitions in garnets were determined from the heat capacity data. Both T_N and T_C systematically decrease with increasing atomic number of R across the series. Lattice, electronic and magnetic contributions to the total heat capacity were calculated. Debye temperatures as a function of absolute temperature were calculated for these compounds. Thermodynamic functions like , , H^o, G^o, , , , , and have been generated for the compounds RFeO₃(s) and R₃Fe₅O₁₂(s) based on the experimental data obtained in this study and the available data in the literature.     

Analysis of primary aliphatic short-chain monoamines by LC in water samples

Several derivatization procedures with o-phthaldialdehyde-N-acetylcysteine (OPA-NAC) were compared for a rapid analysis of primary aliphatic short-chain monoamines in water samples by HPLC using a LiChorospher analytical separation column (100RP₁₈ mm i.d., 5 μm). Both the solution and the solid-support assisted off-line derivatization on C₁₈ SPE cartridges were inadequate options because of beginning degradation processes of the instable isoindol derivatives during their transfer to the analytical column. This problem was precluded with the on-column or solid-support assisted on-line derivatization. In the last mentioned procedure, the derivatization took place in a Hypersil C₁₈ precolumn ( mm i.d., 30 μm) connected with an additional preconcentration step resulting in better detection limits (0.002-0.040 μg ml⁻¹ requiring only 150 μl of water sample) than in the on-column procedure (0.08-0.16 μg ml⁻¹). The improved sample handling, the better control of parameters affecting reaction rates, the fully automation of this method with only 10 min analysis time for each sample are further advantageous. The potential of the solid-support assisted on-line derivatization was outlined and applied to water samples from several sources. Recovery values near 100% were obtained.     

Synthesis and crystal structure of gallosilicate- and aluminogermanate tetrahydroborate sodalites Na8[GaSiO4]6(BH4)2 and Na8[AlGeO4]6(BH4)2

Tetrahydroborate enclathrated sodalites with gallosilicate and aluminogermanate host framework were synthesized under mild hydrothermal conditions and characterized by X-ray powder diffraction and IR spectroscopy. Crystal structures were refined in the space group P-43n from X-ray powder data using the Rietveld method. Na₈[GaSiO₄]₆(BH₄)₂: a=895.90(1) pm, V=0.71909(3)×10⁻⁶ nm³, R_P=0.074, R_B=0.022, Na₈[AlGeO₄]₆(BH₄)₂: a=905.89(2) pm, V=0.74340(6)×10⁻⁶ nm³, R_P=0.082, R_B=0.026. The tetrahedral framework T-atoms are completely ordered in each case and the boron atoms are located at the centre of the sodalite cages. The hydrogen atoms of the enclathrated anions were refined on x, x, x positions, restraining them to boron-hydrogen distances of 116.8 pm as found in NaBD₄.The IR-absorption spectra of the novel phases show the typical bands of the tetrahedral group as found in the spectrum of pure sodium boron hydride.The new sodalites are discussed as interesting -containing model compounds which could release pure hydrogen.     

Structural and conductivity studies of CsKSO4Te(OH)6 and Rb1.25K0.75SO4Te(OH)6 materials

The crystal structures of the title compounds were solved using the single-crystal X-ray diffraction technique. At room temperature CsKSO₄Te(OH)₆ was found to crystallize in the monoclinic system with Pn space group and lattice parameters: ; ; ; β=106.53(2)°; ; Z=4 and . The structural refinement has led to a reliability factor of R₁=0.0284 (wR₂=0.064) for 7577 independent reflections. Rb_1.25K_0.75SO₄Te(OH)₆ material possesses a monoclinic structure with space group P2₁/a and cell parameters: ; ; ; β=106.860(10)°; ; Z=4 and . The residuals are R₁=0.0297 and wR₂=0.0776 for 3336 independent reflections. The main interest of these structures is the presence of two different and independent anionic groups (TeO₆⁶⁻ and SO₄²⁻) in the same crystal.Complex impedance measurements (Z^*=Z^′—iZ^″) have been undertaken in the frequency and temperature ranges 20-10⁶ Hz and 400-600 K, respectively. The dielectric relaxation is studied in the complex modulus formalism M^*.     

Reactions of pyridyl donors with halogens and interhalogens: an X-ray diffraction and FT-Raman investigation

Three different N-donors L, namely N-ethyl-N′-3-pyridyl-imidazolidine-4,5-dione-2-thione (1), N,N′-bis(3-pyridylmethyl)-imidazolidine-4,5-dione-2-thione (2), and tetra-2-pyridyl-pyrazine (3), bearing one, two and four pyridyl substituents, respectively, have been reacted with halogens X₂ (X = Br, I) or interhalogens XY (X = I; Y = Cl, Br). CT σ-adducts L · nXY, bearing linear N?XY moieties (L = 3; X = I; Y = Br, I; n = 2), and salts containing the protonated cationic donors H_nLⁿ⁺ (L = 1 − 3; n = 1, 2, 4), counterbalanced by Cl⁻, Br⁻, , , , , I₂Br⁻, , or anions, have been isolated. Among the reactions products, (H1⁺)Cl⁻, (H1⁺)Br⁻, , , and 3 · 2IBr have been characterised by single-crystal X-ray diffraction. The nature of the products has been elucidated based on elemental analysis and FT-Raman spectroscopy supported by MP2 and DFT calculations.     

Synthesis, structural characterization of some germanium substituted chiral diethyltin derivatives

Some new bimetallic carboxylates of tin and germanium with general formula where R¹ = m-CH₃C₆H₄, p-CH₃C₆H₄, C₆H₅, R² = o-CH₃C₆H₄, p-CH₃C₆H₄, o-CH₃OC₆H₄, C₆H₅, CH₃, have been prepared by the condensation reaction of diethyltin oxide and triarygermyl(substituted)propanoic acid in 1:2 mole ratio, respectively, and characterized by multinuclear (¹H, ¹³C, ¹¹⁹Sn) NMR, ^119mSn Mössbauer and IR spectroscopy. The X-ray crystal structure of the ligand I₄ [(C₆H₅)₃GeCH(o-CH₃OC₆H₄)CH₂COOH] delineate four coordinated germanium atom with a peculiarity of having a molecule of solvent (CHCl₃). The chiral center in the synthesized compounds was identified on the basis of ¹H NMR data and measurements of angle of rotations.     

A computational study of SbnF5n (n = 1-4): Implications for the fluoride ion affinity of nSbF5

This contributions shows with a series of ab initio MP2 and DFT (BP86 and B3-LYP) computations with large basis sets up to cc-pVQZ quality that the literature value of the standard enthalpy of depolymerization of Sb₄F_20(g) to give SbF_5(g) (+18.5 kJ mol⁻¹) [J. Fawcett, J.H. Holloway, R.D. Peacock, D.R. Russell, J. Fluorine Chem. 20 (1982) 9] is by about 50 kJ mol⁻¹ in error and that the correct value of (Sb₄F_20(g)) is +68 ± 10 kJ mol⁻¹. We assign , , and values for Sb_nF_5n with n = 2-4 and compare the results to available experimental gas phase data. Especially the MP2/TZVPP values obtained in an indirect procedure that rely on isodesmic reactions or the highly accurate compound methods G2 and CBS-Q are in excellent agreement with the experimental data, and reproduce also the fine experimental details at temperatures of 423 and 498 K. With these data and the additional calculation of [Sb_nF_5n+1]⁻ (n = 1-4), we then assessed the fluoride ion affinities (FIAs) of Sb_nF_5n(g), nSbF_5(g), nSbF_5(l) and the standard enthalpies of formation of Sb_nF_5n(g) and [Sb_nF_5n+1]⁻_(g): FIA(Sb_nF_5n(g)) = 514 (n = 1), 559 (n = 2), 572 (n = 3) and 580 (n = 4) kJ mol⁻¹; FIA(nSbF_5(g)) = 667 (n = 2), 767 (n = 3) and 855 (n = 4) kJ mol⁻¹; FIA(nSbF_5(l)) = 434 (n = 1), 506 (n = 2), 528 (n = 3) and 534 (n = 4) kJ mol⁻¹. Error bars are approximately ±10 kJ mol⁻¹. Also the related Gibbs energies were derived. Δ_fH°([Sb_nF_5n+1]⁻_(g)) = −2064 ± 18 (n = 1), −3516 ± 25 (n = 2), −4919 ± 31 (n = 3) and −6305 ± 36 (n = 4) kJ mol⁻¹.     

Cationic η-allyl sulfide complexes of nickel(II) for the polymerization of butadiene in aqueous emulsion

Reaction of the dimeric allyl-nickel(II) chloro complex [Ni(η³-C₃H₅)(μ-Cl)]₂ (5) with sulfur donor ligands (L = L₁₀-L₁₃) in the presence of ( = 3,5-(CF₃)₂C₆H₃) gives the corresponding cationic mononuclear complexes of the type [Ni(η³-C₃H₅)(L)₂]⁺ (1-4) [L = L₁₀ = diphenyl sulfide (1); L = L₁₁ = 4,4′-thiodiphenol (2); L = L₁₂ = 4,4′-thio-bis(6-tert-butyl-o-cresol) (3); L = L₁₃ = 4,4′-thio-bis (6-tert-butyl-m-cresol) (4)]. All of these complexes were characterized by elemental analysis and NMR spectroscopy, as well as the representative complex 3 additionally by single-crystal X-ray analysis. In comparison to the known complex [Ni(η³-C₃H₅)(η⁶-BHT)][B] (BHT = 3,5-di-tert-butyl-4-hydroxytoluene), the herein described cationic complexes show an increased stability towards water. The activity of the complexes for butadiene polymerization in aqueous emulsions was studied.     

Thermodynamic properties of lithium mica: Lepidolite

Calorimetric measurements were made on natural sample of lepidolite having the composition (K_0.80Na_0.05Ca_0.07Rb_0.16Cs_0.03)(Li_1.34Al_1.40Fe³⁺_0.01)[Si_3.25Al_0.75O₁₀]F_1.80(OH)_0.20 from Na-Li-type rare-element-rich pegmatites of East Sayany, Russia. High-temperature enthalpy increments were measured with a Tian-Calvet calorimeter at 444-972 K using the drop method. The resultant (T) equation in the interval T = 298.15-972 K was calculated:  = 316.10 + 228.12 × 10⁻³ T − 50.10 × 10⁵ T⁻² (J K⁻¹ mol⁻¹) [± 0.4%] and the value of (298.15 K) = 327.8 J K⁻¹ mol⁻¹ was obtained. The standard molar enthalpy of formation from the elements was determined by high-temperature drop solution calorimetry in molten lead borate at T = 973 K. The value of Δ_f(298.15 K) for lepidolite was found to be −6201 ± 18 kJ mol⁻¹. The thermodynamic properties of lepidolite of idealized composition KLi_1.5Al_1.5[Si₃AlO₁₀]F₂ were estimated based on the experimental data obtained.     

Syntheses, structures, and magnetic properties of the europium(II) selenido pnictogenates(III), EuPnSe3 (Pn=Sb, Bi)

EuPnSe₃ (Pn=Sb, Bi) have been synthesized through the reaction of Eu with Pn₂Se₃ (Pn=Sb, Bi) and Se at 850-900 °C. These compounds are isotypic with SrPnSe₃ (Pn=Sb, Bi) and consist of square pyramidal PnSe₅ units and distorted PnSe₆ octahedra that form hollow columns that extend along the c-axis. These columns are separated by Eu²⁺ cations that occur as nine-coordinate tricapped trigonal prisms. There are also additional V-shaped triselenide Se₃²⁻ anions between the columns that bind the Eu²⁺ cations. The Se?Se contacts (in EuSbSe₃) in these units are 2.4584(11) and 2.4359(11) Å, which are consistent with Se-Se single bonds. The overall structure is chiral. Bond-valence sum calculations indicate that these compounds contain Eu²⁺. Magnetic susceptibility measurements provide values of 7.66 μ_B/Eu for EuSbSe₃ and 7.64 μ_B/Eu for EuBiSe₃, which are close to the expected free-ion moment for Eu²⁺. These compounds follow essentially Curie behavior from 300 to 5 K, and undergo an apparently antiferromagnetic transition below 5 K. Crystallographic data: EuSbSe₃, orthorhombic, space group P2₁2₁2₁, , , , , Z=16, R(F)=2.63% for 183 parameters and 5095 reflections with I>2σ(I); EuBiSe₃, orthorhombic, space group P2₁2₁2₁, , , , , Z=16, R(F)=2.68% for 183 parameters and 4895 reflections with I>2σ(I).     

Synthesis, crystal structure and optical properties of BiMgVO5

The new vanadate BiMgVO₅ has been prepared and its structure has been determined by single crystal X-ray diffraction: space group P2₁/n, , , , β=107.38(5)°, wR₂=0.0447, R=0.0255. The structure consists of [Mg₂O₁₀] and [Bi₂O₁₀] dimers sharing their corners with [VO₄] tetrahedra. The ranges of bond lengths are 2.129-2.814 Å for Bi-O; 2.035-2.167 Å for Mg-O and 1.684-1.745 Å for V-O. V-O bond lengths determined from Raman band wavenumbers are between 1.679 and 1.747 Å. An emission band overlapping the entire visible region with a maximum around 650 nm is observed.     

A one-dimensional zirconium hydroxyfluoride, [Zr(OH)2F3][enH]

The first example of a unidimensional zirconium hydroxide fluoride was synthesized under mild solvothermal treatment and characterized by X-ray diffraction and thermal techniques. Monoprotonated ethylenediamine cations reside between the anionic chains. Crystal data for this material are as follows: [C₂N₂H₉][Zr(OH)₂F₃], M=243.35, orthorhombic, space group Pca2₁, a=6.8016(13), b=6.1393(12), , , , Z=4, , μ(Mo-Kα)=1.777 mm⁻¹, . The material transforms to an unknown layered material at ∼175 °C, a common occurrence for 1D structures where the chains are arranged in hydrogen-bonded layers and separated by interlayer organoammoniums. Collapse to the known condensed mineral phase Zr(FO)_2.7 occurs at ca. 275 °C before finally transforming to the baddeleyite form of ZrO₂ at ca. 460 °C.     

New hydrophobic ionic liquids based on perfluoroalkyltrifluoroborate anions

New hydrophobic ionic liquids, 1-ethyl-3-methylimidazolium (EMI⁺) perfluoroalkyltrifluoroborate ([R_fBF₃]⁻) (R_f=C₂F₅,n-C₃F₇, and n-C₄F₉) were prepared in high yield and purity by facile neutralization of 1-ethyl-3-methylimidazolium (EMI⁺) methylcarbonate (MeOCO₂⁻) with aqueous H_solv.[R_fBF₃]_solv. solutions. All the salts prepared were characterized by , , NMR, MS and elemental analysis, and thermal and electrochemical properties of these salts have been measured. [EMI][C₂F₅BF₃] melted at lower temperature (−1 °C) than [EMI][BF₄] (13 °C), resulting in higher conductivity at low temperature. Its application to double-layer capacitors (DLCs) was examined.