Influence of valence and coordination of manganese ions on spectral and dielectric features of Na2SO4–B2O3–P2O5 glasses

Sodiumsulpho borophosphate glasses with composition (40 ? x)Na₂SO₄–30B₂O₃–30P₂O₅: xMnO with x ranging from 0 to 5.0 mol% were manufactures. Dielectric spectra have been studied over a wide frequency range of 10²–10⁵ Hz and in the temperature range within 30–250 °C. The valance states of manganese ions and their ligand coordination in the glass network have been investigated using optical absorption, luminescence and ESR spectroscopy. The analysis of the these results has indicated that the manganese ions exist both in Mn²⁺ as well as in Mn³⁺ states and occupy prevailingly octahedral positions and serve as modifiers similarly to Na⁺ ions The values of dielectric parameters (dielectric constant, ε′(ω), loss tan δ and ac conductivity, σ_ac) were found to increase with increasing MnO content. They play a role of modifiers similarly to Na⁺ ions, create bonding defects and free ions viz., [SO₄]^2?, [POO_1/2O₂]^2?, [POO_0/2O₃]^3–, Na⁺ and (NaSO₄)^?. The migration of these charge carriers would build up space charge polarization and may be responsible for the enhanced dielectric parameters. The ac conductivity also is enhanced with increasing MnO content. The mechanism responsible for such increase is well explained based on the modifying action of Mn²⁺ ions.     

Influence of X-ray irradiation on the optical properties of chromium-doped KliSO4 crystals

The absorption and circular-dichroism spectra of chromium-activated KLiSO₄ crystals both nonirradiated and irradiated with an X-ray beam have been studied. It was established that in nonirradiated crystals chromium ions are mainly trivalent (Cr³⁺) and have octahedral coordination. In irradiated crystals, along with the centers provided by (Cr³⁺) ions, new centers are formed associated with (^Cr4+) and (^Cr5+) ions.     

Two-dimensional crown ether complex. Synthesis and crystal structure of [Na(N15C5)]<Subscript>2</Subscript>[Cu(mnt)<Subscript>2</Subscript>]

A novel crown ether complex [Na(N15C5)]₂[Cu(mnt)₂] (1) (where N15C5 = 2,3-naphtho-15-crown-5 and mnt = maleonitriledithiolate, [C₂S₂(CN)₂]^2–) was synthesized and characterized by elemental analysis, FT-IR spectra, UV-visible spectra and single crystal X-ray diffraction. Structural analysis reveals that the complex 1 consists of two [Na(N15C5)]⁺ complex cations and one [Cu(mnt)₂]^2– complex anion and the complex molecules are assembled into a novel 2D network by Na–N interactions. In the network, there are 34-member macrocycles formed by four sodium ions of complex cations and four complex anions through Na–N bonds. In each macrocycle, – stacking interactions occurred between two parallel naphthylene moieties of N15C5. It is interesting that the 2D network displays an open-capped wave-like sheet viewed along the crystallographic a axis.     

Effect of quenching rate and annealing on ESR of Cu2+ and γ-induced Cd+ in low alkali borate glasses

A new ESR hyperfine structure (hfs) of Cu²⁺ was detected in moderately (cooling rate ≈ 3 K/s) and rapidly (10³–10⁵K/s) quenched borate glasses with Na₂O content smaller than 5 mol% in addition to the already reported three patterns, spectra I, II and III, for the moderately quenched borate glasses with 5 ? [Na₂O]?13, 20 ? [Na₂O] ?37 and 55 ? [Na₂O] ? 75, respectively. The ESR parameters of this spectrum were much the same as those of II, but a significant difference was observed between thermal stabilities of these spectra. The newly observed spectrum was named spectrum II′. A superposition of spectra II′ and I was seen in low alkali borate glasses ([Na₂O] ? 5 mol%). The relative intensity of II′ to I increased remarkably with increasing quenching rate of the melts and with decreasing alkali content under the same quenching condition. In addition, spectrum II′ was found to relax into I upon thermal annealing of the glasses. Similar changes were observed also in ESR of the γ-induced Cd⁺ with 5s¹ electronic configuration. A tentative model to account for the spectral changes was proposed on the basis of the characteristics of B—O bonding.     

Crystal structures of dioxonium hexafluorotantalate and dioxonium hexafluoroniobate complexes with tetrabenzo-30-crown-10

Two isostructural complexes of dioxonium [H₅O₂]⁺ with tetrabenzo-30-crown-10 of the compositions [(tetrabenzo-30-crown-10 · H₅O₂)][TaF₆] (I) and [(tetrabenzo-30-crown-10 · H₅O₂)][NbF₆] (II) are studied using X-ray diffraction. The complexes crystallize in the monoclinic crystal system (space group C2/c, Z = 4). The unit cell parameters of these compounds are as follows: a = 15.6583(12) Å, b = 15.2259(13) Å, c = 16.4473(13) Å, and β = 99.398(6)° for complex I and a = 15.7117(12) Å, b = 15.2785(15) Å, c = 16.5247(15) Å, and β = 99.398(7)° for complex II. These complexes belong to the ionic type. The dioxonium cation [H₅O₂]⁺ in the form of the two-unit cluster [H₃O · H₂O]⁺ is stabilized by the strong hydrogen bond OH?O [O?O, 2.353(4) Å] and encapsulated by the crown ether. Each oxygen atom of the dioxonium cation also forms two oxygen bonds O?O(crown). The crown ether adopts an unusual two-level (pocket-like) conformation, which provides a complete encapsulation of the oxonium associate. The interaction of the cationic complex with the anion in the crystal occurs through contacts of the C-H?F type.     

Crystal structure of the binary complex of cobalt and zinc chlorides with carbamide [Co(OCN<Subscript>2</Subscript>H<Subscript>4</Subscript>)<Subscript>5</Subscript>(H<Subscript>2</Subscript>O)][ZnCl<Subscript>4</Subscript>]

Mixed single crystals of [Co(OCN₂H₄)₅(H₂O)][ZnCl₄] were grown by the isothermal evaporation of an aqueous solution. The crystal structure of this complex was established by X-ray diffraction (R = 0.052 based on 7003 reflections). The crystals consist of [Co(OCN₂H₄)₅(H₂O)]²⁺ cations containing Co atoms in an octahedral coordination and [ZnCl₄]²⁻] anions containing Zn atoms in a tetrahedral coordination. The carbamide molecules are involved in both intramolecular and interionic hydrogen bonds. The H₂O molecule forms hydrogen bonds with the anions.     

Determination of silicate anion constitution in glassy and crystalline lead silicates using an improved TMS technique

Using the DMF trimethylsilylation technique developed by Tamás, Sarkar and Roy, the distribution of silicate anions in lead silicate glasses of the composition range PbO·SiO₂4PbO· SiO₂ has been reinvestigated. The obtained results agree with earlier findings except for the tetrameric chain anion [SiO₄O₁₃]^10?, which had not been found before. Crystallization of glassy PbO·SiO₂ proceeds via the formation of low-molecular silicate anions [Si₂O₇]^6?, [Si₄O₁₃]_(II)^10? and [Si₇O₂₂]^16?, which characterize the low-temperature crystalline polymorph TPbO·SiO₂. Further heat treatment turns TPbO·SiO₂ into alamosite, characterized by polysilicate chain anions [SiO₃^2?]_∞.     

Optical and structural properties of Sr-Nb-phosphate glasses

This research studied optical and structural properties of SrO-Nb₂O₅-P₂O₅ glasses containing 0 ~ 25 mol% Nb₂O₅ and 35 ~ 60 mol% SrO using spectra of UV-Vis, FTIR and XPS. Our aim was to work new moldable glasses which are colorless with high refractive index and transmittance, and their correlation with glass structure. Nb₂O₅ plays the role as an intermediate of glass formation, and transforms the role to network-former or glass-modifier depending on composition. Refractive index increases monotonically with Nb₂O₅ content at the expense of transmittance, and specific coloring which occurs in ternary compositions with the ratio P₂O₅/SrO > 1. This effect arises from much increased [Nb³⁺ and Nb⁴⁺] fraction, as quantitatively deconvoluted in Nb3d XPS spectra, in the ligand [NbO₆]_octahedral which is supported by FTIR and O1s XPS spectra. As the ratio P₂O₅/SrO ≤ 1, Nb₂O₅ is more of a network former and [NbO₆]_octahedral structure turns into [NbO₄]_tetrahedron with partial Nb-O…(Sr) bonding turns into (Nb-O-Nb)_tetrahedron, coloring disappears.     

Solvothermal synthesis and growth mechanism of asymmetric ZnO hierarchical structures in diethylene glycol with ammonia solution

Several novel asymmetric ZnO hierarchical structures were synthesized in diethylene glycol (DEG) with different amount of ammonia solution via solvothermal process. The submicron‐rods or nanorods as the building units are distributed on the two sides in an asymmetric manner, resulting in formation of the shiitake‐like or bouquet‐like morphology. A possible formation mechanism was proposed on the basis of the experimental result. The consumption of the precursor could lead to a two‐step nucleation and growth process. The relative content of the [Zn(OH)₄]²⁻ and the [Zn(NH₃)₄]²⁺ precursors varies with the amount of ammonia solution, which affect the size and morphology of the asymmetric structures. The [Zn(OH)₄]²⁻ complex and the [Zn(NH₃)₄]²⁺ complex are absorbed on the positive (0001)‐Zn polar surface and the negative (000–1)‐O polar surface respectively, which lead to the alteration of growth rate of these polar surfaces.     

Synthesis and thermal,phase transition and FTIR spectral characterization of tetraethylammonium tetrachlorocuprate (II) crystals

Single crystals of tetraethylammonium tetrachlorocuprate (II), [N(C₂H₅)₄]₂CuCl₄, were grown by slow evaporation method at room temperature. The crystals were characterized through powder XRD, thermogravimetric (TG‐DTA), low temperature differential scanning calorimetric (DSC) studies and FTIR spectroscopy. While the powder XRD pattern of the compound shows sharp Bragg peaks confirming the crystallinity of the compound, the TG‐DTA studies confirm formation of the compound in the stoichiometric ratio. The thermal anomalies observed in DSC curve at ‐120°C in the heating cycle and around ‐30°C in the cooling cycle indicate a first order phase transition. The phase transition was predicted to be associated with the ordering of CuCl₄^2‐ and successive long range orientation of [N(C₂H₅)₄]⁺ ions which are disordered at high temperatures. The cationic [N(C₂H₅)₄]⁺ plays a role in phase transitions at low temperatures. The sharp exothermic peak observed in high temperature DSC indicates a structural phase transition when [N(C₂H₅)₄]CuCl₃ is formed on heating the compound. The FTIR spectra of the compound characterize the various chemical bonding and water molecules adsorbed in the compound. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and crystal structure of a new composite complex between a hepta-coordinate ytterbium(III) and a heteropoly molybdic anion: [Yb(DMSO)<Subscript>7</Subscript>]H[SiMo<Subscript>12</Subscript>O<Subscript>40</Subscript>] (DMSO = dimethyl sulfoxide)

A new composite complex of the general formula [Yb(DMSO)₇]H[SiMo₁₂O₄₀] has been synthesized from H₄SiMo₁₂O₄₀⋅nH₂O, YbCl₃ and DMSO in mixed solvent of acetonitrile and water and characterized by elemental analysis, IR spectra and single crystal X-ray diffraction. Singe crystal X-ray structure analysis shows that it belongs to monoclinic system, space group P2₁/c, with a = 11.685(2) Å, b = 14.969(3) Å, c = 35.037(7) Å, β = 98.50(3)^∘, and Z = 4. There is one [Yb(DMSO)₇]³⁺ coordinated cation and one [SiMo₁₂O₄₀]⁴⁻ polyanion in one structure unit. The organic ligands (DMSO) do coordinate directly with ytterbium(III) to form a distorted pentagonal bipyramid complex ion by coordination bond, then combines to the SiMo₁₂O₄₀⁴⁻ anion by static electric force. The results of IR and X-ray diffraction show that there is strong interaction between polyoxometalate and organic donors.     

Structural features of 3d metal compounds with 1-hydroxyethylidenediphosphonic acid

Structural features of 3d metal complexes with anions of 1-hydroxyethylidenediphosphonic acid (HEDP, H₄ L), in which the M: HEDP ratios are equal to 1: 2, 1: 1, 3: 2, and 5: 2, are discussed. The Cu(II): HEDP = 1: 2 complexes are characterized by five types of structures: monomeric structures trans-[Cu(H_{4 ? n} L)₂(H₂O)₂]^{2 ? 2n} , cis-[Cu(H_{4 ? n} L)₂(H₂O)₂]^{2 ? 2n} , and [Cu(L)₂]^6?; the dimeric structure { [Cu(H₂ L)(H₂O)]₂(μ ₂-H₂ L)₂}^4? ; and the polymeric chain structure {[Cu(μ ₂-H₂ L)₂]^2?}_∞. Six coordination modes exhibited by HEDP in the Cu(II) compounds are described.     

X-ray diffraction study of the heterovalent copper compound [Cu4(OH)4 Bipy 4][Cu2(B10H10)3] · 4CH3CN

X-ray diffraction studies of three samples of the [Cu₄(OH)₄ Bipy ₄][Cu₂(B₁₀H₁₀)₃]·4CH₃CN crystals reveal a small amount (4?C6%) of the second component, which is related to the main component by a mirror pseudoplane. An analysis of the geometric structure and mutual arrangement of complex cations [Cu₄(OH)₄ Bipy ₄]⁴⁺ and anions [Cu₂(B₁₀H₁₀)₃]^4? in the cell shows that replacing structural elements by their mirror equivalents results in insignificant steric conflicts. The existence of this minor crystal component can be attributed to point substitution defects or a separate twin individual.     

Synthesis and the crystal and molecular structures of a germanium(IV)-copper(II) heteronuclear diethylenetriaminepentaacetate complex, [Cu(μ-H<Emphasis Type="Italic">Dtpa</Emphasis>)<Subscript>2</Subscript>{Ge(OH)}<Subscript>2</Subscript>] · 12H<Subscript>2</Subscript>O

A procedure for synthesizing a mixed Cu-Ge complex with diethylenetriaminepentaacetic acid (H₅Dtpa) is worked out, the compound [Cu{Ge(OH)(HDtpa)}₂] · 12H₂O is synthesized, and its crystal structure is studied by X-ray diffraction. In the centrosymmetric trinuclear molecular complex, the octahedral coordination of the peripheral Ge atom involves three O and two N atoms of the HDtpa^4? ligand and the O atom of the hydroxo ligand. The central Cu atom is coordinated by four O and two N atoms of two HDtpa^4? ligands, which form a tetragonal bipyramid (4 + 2). The HDtpa^4? ligand fulfills an octadentate hexachelate bridging function (3N, 5O). The molecular complexes and crystallization water molecules are linked by an extended hydrogen-bond network.     

Microstructure and thermal properties of the GeS2–In2S3–CsI glassy system

A new series of chalcohalide glasses in the GeS₂–In₂S₃–CsI pseudo-ternary system were prepared by conventional melt-quenching method. The glass-forming region was determined and it is mainly situated in the GeS₂-rich domain. The glasses have relatively high glass transition temperatures (T_g ranges from 335 to 405 °C) and good thermal stabilities. Based on the Raman spectra, it can be speculated that the glassy net is mainly constituted by [GeS₄] and [InS_4?xI_x] tetrahedra, which are interconnected by the bridging sulfur atoms. And the ethane-liked structural units [S₃Ge–GeS₃] can be formed because of the lacking of sulfur. Cs⁺ ion, which was added from CsI, exists as the nearest neighbor of I^? ion.     

Synthesis and crystal structures of nitratocobaltates Na2[Co(NO3)4], K2[Co(NO3)4], and Ag[Co(NO3)3] and potassium nitratonickelate K2[Ni(NO3)4]

The cobalt(II) and nickel(II) nitrate complexes with an island structure (Na₂[Co(NO₃)₄] (I) and K₂[Co(NO₃)₄] (II)] and a chain structure [Ag[Co(NO₃)₃] (III) and K₂[Ni(NO₃)₄] (IV)] are synthesized and investigated using X-ray diffraction. In the anionic complex [Co(NO₃)₄]^2? of the crystal structure of compound I, the Co coordination polyhedron is a twisted tetragonal prism formed by the O atoms of four asymmetric bidentate nitrate groups. In the anion [Co(NO₃)₄]^2? of the crystal structure of compound II, one of the four NO₃ groups is monodentate and the other NO₃ groups are bidentate (the coordination number of the cobalt atom is equal to seven, and the cobalt coordination polyhedron is a monocapped trigonal prism). The crystal structures of compounds III and IV contain infinite chains of the compositions [Co(NO₃)₂(NO₃)_2/2]^? and [Ni(NO₃)₃(NO₃)_2/2]^2?, respectively. In the crystal structure of compound III, seven oxygen atoms of one monodentate and three bidentate nitrate groups form a dodecahedron with an unoccupied vertex of the A type around the Co atom. In the crystal structure of compound IV, the octahedral polyhedron of the Ni atom is formed by five nitrate groups, one of which is terminal bidentate. The data on the structure of Co(II) coordination polyhedra in the known nitratocobaltates are generalized.     

Infrared spectra of silver complexes with 2-aminopyridine and crystal structure of the 4:3 aminopyridine-silver nitrate compound

The 43 complex formed between 2-aminopyridine (ampy) and AgNO₃ belongs to the orthorhombic space groupPccn. The unit cell of dimensionsa=7.992(4),b=16.788(5),c=21.034(8) Å contains four formula units. The structure was refined on 998 nonzero reflections toR=0.038. The crystal contains the dimeric [Ag₃(ampy)₄]³⁺ cation. Two of the three independent Ag atoms are each coordinated to two ampy ligandsvia the heterocyclic nitrogen lone pair (mean Ag-N=2.18 Å), and the N-Ag-N angle in this [ampy-Ag-ampy]⁺ unit is 154.0°. By using the two available amino groups, the [ampy-Ag-ampy]⁺ unit acts as a bidentate ligand, and two such units related by a twofold axis achieve a roughly tetrahedral environment of NH₂ lone pairs about the third Ag atom (mean Ag-N=2.39 Å). The infrared spectra of [Ag₃(ampy)₄](NO₃)₃, [Ag(ampy)₂]ClO₄, [Ag₃(ampy-H)₂]NO₃, and [Ag₃(ampy-H)₂]ClO₄, and those of their amino-deuterated derivatives, are discussed. Diagnostic regions are proposed to identify coordinationvia the amino group and the heterocyclic nitrogen atom.     

Synthesis and structure of [(NH<Subscript>2</Subscript>)<Subscript>2</Subscript>CSSC(NH<Subscript>2</Subscript>)<Subscript>2</Subscript>]<Subscript>2</Subscript>[OsBr<Subscript>6</Subscript>]Br<Subscript>2</Subscript> · 3H<Subscript>2</Subscript>O

The complex [(NH₂)₂CSSC(NH₂)₂]₂[OsBr₆]Br₂ · 3H₂O is synthesized by the reaction of K₂OsBr₆ with thiocarbamide in concentrated HBr and characterized using electronic absorption and IR absorption spectroscopy. Its crystal structure is determined by X-ray diffraction. The crystals are orthorhombic, a = 11.730(2) Å, b = 14.052(3) Å, c = 16.994(3) Å, space group Cmcm, and Z = 4. The [OsBr₆]^2? anionic complex has an octahedral structure. The Os-Br distances fall in the range 2.483–2.490 Å. The α,α′-dithiobisformamidinium cation is a product of the oxidation of thiocarbamide. The S-S and C-S distances are 2.016 and 1.784 Å, respectively. The H₂O molecules, Br^?ions, and NH₂ groups of the cation are linked by hydrogen bonds.     

Vanadium contribution in different glasses in view of the ligand field theory

Spectrophotometric and magnetic studies were carried out on different glasses containing known amounts of V₂O₅ in order to throw some light on the valence states and coordination of vanadium in such glasses (in view of the ligand field theory).The results obtained were found to be in agreement with those of aqueous solutions, e.g. [V(H₂O)₆]³⁺, [VO(H₂O)₅]²⁺, and VO²⁺ which showed a slight difference in band positions due to the distortion as well as the difference between the ligand field strength of glass and water. Generally it may be concluded that vanadium is present in borate and silicate glasses in three possible valencies, V⁵⁺, V⁴⁺ and V³⁺, while in phosphate glasses it is generally present in two valencies V⁴⁺ and V³⁺.     

Crystal structure of urusovite Cu[AlAsO5: A new type of a tetrahedral aluminoarsenate polyanion

The crystal structure of the new mineral urusovite Cu[AlAsO₅] has been determined (monoclinic system, sp. gr. P2₁/c, a = 7.335(1) Å, b = 10.255(1) Å, c = 5.599(1) Å, β = 99.79(1)°, V = 415.0(1) ų, Z = 4). The structure is solved by direct methods and refined to R = 0.048 (wR = 0.103). The structure is built by open-branched {uB, _∞ ² } [AlAsO₅]^2? layers parallel to the (100) plane. The layers consist of two-link chains of _∞ ¹ [Al₂O₆] tetrahedra, which are parallel to the z-axis and are connected through the [AsO₄]-groups. The sharing-edges [CuO₅] tetragonal pyramids link the aluminoarsenate layers to form a three-dimensional framework. The established layer is the second example of an tetrahedral aluminoarsenate polyanion.