Polarised IR and Raman spectra of non-centrosymmetric Na3Li(SeO4)2.6H2O crystal--a new Raman laser material

Polarised IR and Raman spectra of Na₃Li(SeO₄)₂·6H₂O single crystal have been recorded. Discussion of the results has been based on the factor group approach for the trigonal R3c (C_3v⁶) space group with Z = 2. The obtained results for the spontaneous Raman scattering have been used in the discussion of the stimulated Raman spectra of the material studied—a new Raman laser crystal.     

Raman spectroscopic study of the tellurite minerals: emmonsite Fe23+Te34+O9·2H2O and zemannite Mg0.5[Zn2+Fe3+(TeO3)3]4.5H2O

Raman spectroscopy has been used to study zemannite Mg_0.5[Zn²⁺Fe³⁺(TeO₃)₃]4.5H₂O and emmonsite Fe₂³⁺Te₃⁴⁺O₉·2H₂O. Raman bands for zemannite and emmonsite, observed at 740 and 650 cm⁻¹ and at 764 and 788 cm⁻¹, respectively, are attributed to the ν₁ (TeO₃)²⁻ symmetric stretching mode. The splitting of the symmetric stretching mode for emmonsite is in harmony with the results of X‐ray crystallography which shows three non‐equivalent TeO₃ units in the crystal structure. Two bands at 658 and 688 cm⁻¹ are assigned to ν₃ (TeO₃)²⁻ anti‐symmetric stretching modes. Raman bands observed at 372 and 408 cm⁻¹ for zemannite and 397 and 414 cm⁻¹ for emmonsite are attributed to the (TeO₃)²⁻ν₂(A₁) bending mode. The two Raman bands at 400 and 440 cm⁻¹ for emmonsite are ascribed to the ν₄(E) bending modes, while the band at 326 cm⁻¹ is due to the ν₂(A₁) bending vibration. Copyright © 2008 John Wiley & Sons, Ltd.     

Crystal and molecular structure of 2‐amino‐5‐chloropyridinium hydrogen selenate—its IR and Raman spectra,DFT calculations and physicochemical properties

The new organic‐inorganic salt, 2‐amino‐5‐chloropyridinium hydrogen selenate, has been synthesised and characterised by means of FT‐IR, FT‐Raman and single crystal X‐ray crystallography. Its vibrational spectra have been discussed on the basis of quantum chemical DFT calculations using the B3LYP/6‐31G(d,p) approach. The crystal and molecular structures have been compared and the role of the intermolecular interactions in this crystal has been analysed. The N HO interactions between the hydrogen atoms of the organic cation and oxygen atoms of hydrogen selenate anion determine the supramolecular arrangement in three‐dimensional space. The possible application of the studied composite material as a Raman laser has been discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

聚合羟基铁改性蒙脱石的制备、表征及吸附Se(Ⅵ)的特性

采用共沉淀法制备了3种聚合羟基铁改性蒙脱石(Mt-Fex,x=1,2,3),对比研究了纯蒙脱石(Mt)和Mt-Fex(x=1,2,3)的表面性质及吸附Se(Ⅵ)的特性。结果表明,Mt样品的d(001)层间距为1.296 nm,在Mt-Fex中升高至1.430 nm以上;与Mt样品比较,MtFex的孔体积、表面积、表面分形度均随含铁量的增加而升高,其中微孔体积和微孔表面积的变化尤为明显;Mt样品的等电点(IEP)低于3,而Mt-Fe3的IEP升高至6.8;初始p H=5.0时,Mt和Mt-Fex(x=1,2,3)的表面ζ电位分别为-33.5,-11.7,9.9和33.2m V。单吸附位Langmuir模型能够很好地拟合Mt样品对Se(VI)的等温吸附数据(R2=0.993),4种样品吸附数据的单吸附位Langmuir拟合判断系数(R2)随样品含铁量的增加而降低;3种Mt-Fex样品的吸附数据更适合用双吸附位Langmuir模型拟合(R2=0.993~0.997);Freundlich模型对4种样品的吸附数据拟合度较低(R2=0.849~0.970),其判断系数(R2)随样品含铁量的增加而升高。初始p H=5.0时,Mt和Mt-Fex(x=1,2,3)对Se(Ⅵ)的吸附容量分别为4.23,7.83,10.38和14.34 mg·g-1。可见,聚合羟基铁含量较高的Mt-Fex样品对土-水体系中Se(Ⅵ)的固定能力明显高于Mt。     

Extended networks, porous sheets, and chiral frameworks. Thorium materials containing mixed geometry anions: Structures and properties of Th(SeO3)(SeO4), Th(IO3)2(SeO4)(H2O)3·H2O, and Th(CrO4)(IO3)2

Three novel Th(IV) compounds containing heavy oxoanions, Th(SeO₃)(SeO₄) (1), Th(IO₃)₂(SeO₄)(H₂O)₃·H₂O (2), and Th(CrO₄)(IO₃)₂ (3), have been synthesized under mild hydrothermal conditions. Each of these three distinct structures contain trigonal pyramidal and tetrahedral oxoanions. Compound 1 adopts a three-dimensional structure formed from ThO₉ tricapped trigonal prisms, trigonal pyramidal selenite, SeO₃^2-, anions containing Se(IV), and tetrahedral selenate, SeO₄^2-, anions containing Se(VI). The structure of 2 contains two-dimensional porous sheets and occluded water molecules. The Th centers are found as isolated ThO₉ tricapped trigonal prisms and are bound by four trigonal pyramidal iodate anions, two tetrahedral selenate anions, and three coordinating water molecules. In the structure of 3, the Th(IV) cations are found as ThO₉ tricapped trigonal prisms. Each Th center is bound by six IO₃^1- anions and three CrO₄^2- anions forming a chiral three-dimensional structure. Second-harmonic generation of 532 nm light from 1064 nm radiation by a polycrystalline sample of 3 was observed. Crystallographic data (193 K, MoKα, λ=0.71073): 1; monoclinic, P2₁/c; , , , β=103.128(1), Z=4, R(F)=2.47% for 91 parameters with 1462 reflections with I>2σ(I); 2, monoclinic, P2₁/n, , , , β=100.142(2), Z=4, R(F)=4.71% for 158 parameters with 2934 reflections with I>2σ(I); 3, orthorhombic, P2₁2₁2₁, , , , Z=4, R(F)=2.04% for 129 parameters with 2035 reflections with I>2σ(I).     

Thermodynamical study on the magnesium selenate-nickel selenate-water system at 25°C

Summary Activity coefficients of the salt components in both the saturated solutions and the (Mg_xNi_1–x)SeO₄·6H₂O mixed crystals of the MgSeO₄-NiSeO₄-H₂O system at 25°C have been determined by the isopiestic method. It has been established that the formed mixed crystals deviate only slightly from ideality and can be adequately described by a regular model. ThePitzer ion-interaction model has been used to calculate the thermodynamic properties of the salt components in the ternary system. The calculated data are in good agreement with those obtained experimentally by the isopiestic method.

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Thermodynamische Untersuchungen am Magnesiumselenat-Nickelselenat-Wasser-System bei 25°C

Zusammenfassung Die Aktivitätskoeffizienten der Salzkomponenten sowohl der gesättigten Lösungen als auch der Mischkristalle (Zusammensetzung: (Mg_xNi_1–x)SeO₄·6H₂O) des Systems MgSeO₄-NiSeO₄-H₂O wurden bei 25°C mit Hilfe der isopiestischen Methode bestimmt. Es konnte gezeigt werden, daß die gebildeten Mischkristalle nur leicht vom idealen Zustand abweichen und mit einem regulären Modell gut beschrieben werden können. Zur Berechnung der thermodynamischen Eigenschaften der Salzkomponenten des ternären Systems wurde dasPitzersche lonenwechselwirkungsmodell herangezogen. Die berechneten Werte stimmen mit den mittels der isopiestischen Methode gewonnenen experimentellen Ergebnissen gut überein.

     

The first organically templated linear metal selenate

An organically templated cadmium selenate of the formula [enH₂][Cd(H₂O)₂(SeO₄)₂], , has been synthesized by carrying out the reaction between CdO and H₂SeO₄ in the presence of the amine in aqueous medium at 80°C. The structure of involves isolated infinite [Cd(H₂O)₂(SeO₄)₂]²⁻ chains running along the c-axis, with the protonated ethylenediamine molecules between them. Crystal data for are as follows: Monoclinic, space group=C2/c, a=10.5059(7), b=10.3605(7), , β=94.666(2)°, , z=8, R₁=0.0237, wR₂=0.0500 (for all data).     

Polarized IR-microscope spectra of guanidinium hydrogenselenate single crystal

The polarized IR-microscope spectra of C(NH2)3.HSeO4 small single crystal samples were measured at room temperature. The spectra are discussed with the framework of oriented gas model approximation and group theory. The stretching nuOH vibration of the hydrogen bond with the O...O distance of 2.616 A gives characteristic broad AB-type absorption in the IR spectra. The changes of intensity of the AB bands in function of polarizer angle are described. Detailed assignment for bands derived from stretching and bending modes of selenate anions and guanidinium cations were performed. The observed intensities of these bands in polarized infrared spectra were correlated with theoretical calculation of directional cosines of selected transition dipole moments for investigated crystal. The vibrational studies seem to be helpful in understanding of physical and chemical properties of described compound and also in design of new complexes with exactly defined behaviors.     

The Crystal Structure, Vibrational Spectra, and Thermal Behavior of Piperazinium(2+) Selenate Monohydrate and N, N′-Dimethylpiperazinium(2+) Selenate Dihydrate

The crystal structure of piperazinium(2+) selenate monohydrate has been resolved; this substance crystallizes in the monoclinic space group P2₁/n, a=6.4586(8), b=11.8335(7), c=11.8065(7) Å, β=100.990(8)°; V=885.80(13) Å⁵, Z=4, R=0.0446 for 1556 observed reflections. A similar compound, N,N′-dimethylpiperazinium(2+) selenate dihydrate, crystallizes in a triclinic system with space group P and lattice parameters a=6.7370(8), b=7.9845(9), c=12.3802(12) Å, α=92.435(9)°, β=100.219(9)°, γ=114.699(10)°; V=590.34(11) ų, Z=2, R=0.0311 for 2071 observed reflections. While, in the former structure, the cations of piperazinium(2+) in the chair conformation are arranged roughly plane-parallel above one another, in the second substance, the N,N′-dimethylpiperazinium (2+) ions lie approximately perpendicularly above one another. The FTIR and FT Raman spectra of both test substances have been measured and studied. The thermoanalytical properties were studied using TG, DTG, and DTA methods in the temperature range 293–533 K. DSC measurements were carried out in the temperature range 95–343 K. No phase transition was found in this temperature region for either of the compounds.     

On the Double Salt Formation in the Systems Rb2SeO4=ZnSeO4=H2O andCs2SeO4=ZnSeO4=H2O at 25°C

Summary.  The solubilities in the systems Rb₂SeO₄=ZnSeO₄=H₂O and Cs₂SeO₄=ZnSeO₄=H₂O at 25°C were studied by the method of isothermal decrease of supersaturation. Comparatively wide crystallization fields of the double salts Rb₂Zn(SeO₄)₂ċ6H₂O and Cs₂Zn(SeO₄)₂ċ6H₂O are observed in the solubility diagrams. The double salts form monoclinic crystals which are isostructural with those of the corresponding rubidium and cesium zinc sulfate hexahydrates. TG and TDA measurements indicate that the double salts lose their crystallization water in one step in the temperature intervals of 50–160°C (rubidium salt) and 70–150°C (cesium salt). Received March 14, 2000. Accepted (revised) June 5, 2000