Vibrational spectra of MII3Pb(P2O7)2 (MII = Ni,Co)

Raman and IR spectra of polycrystalline Ni₃Pb(P₂O₇)₂ and Co₃Pb(P₂O₇)₂ have been recorded and analyzed. The internal modes are assigned in terms of PO₃ and POP vibrations. The results point to a bent POP bridge configuration in Co₃Pb(P₂O₇)₂ as in Ni₃Pb(P₂O₇)₂. In the cobalt compound, the P₂O⁴⁻₇ ions are distorted. Non-coincidence of the majority of the Raman and IR bands confirms a centrosymmetric structure for Ni₃Pb(P₂O₇)₂, and Co₃Pb(P₂O₇)₂. The POP bridge angle is slightly higher in the cobalt compound than in the nickel compound.     

Preparation,Crystal Structure and Vibrational Spectra of Ca2P2O6·2H2O and [Ca(H2O)3(H2P2O6)]·0.5(C12H24O6)·H2O

The calcium salts Ca₂P₂O₆ · 2H₂O ( 1 ) and [Ca(H₂O)₃(H₂P₂O₆)] · 0.5(C₁₂H₂₄O₆) · H₂O ( 2 ) were prepared and structurally characterized by single‐crystal X‐ray diffraction. Compound 1 crystallizes in the orthorhombic space group Pbca and compound 2 in the monoclinic space group P2₁/n. The crystal structure of compound 1 consists of chains of edge‐sharing [CaO₇] polyhedra linked by hypodiphosphate(IV) anions to form a three‐dimensional network. The crystal structure of compound 2 consists of alternated layers of crown ether and water molecules and respective ionic units. Within the layers of ionic units the Ca²⁺ cations are octahedrally coordinated by three monodentate dihydrogenhypodiphosphate(IV) anions and three water molecules. The IR/Raman spectra of the title compounds were recorded and interpreted, especially with respect to the [P₂O₆]^4– and [H₂P₂O₆]^2– groups. The phase purity of 2 was verified by powder diffraction measurements.     

Degradation thermique et etude vibrationnelle de MII(NH4)4(P3O9)2x4H2O(M II=Cu2+, Ni2+, Co2+)

We have studied the thermal behaviour under atmospheric pressure of isotypic tetrahydrate cyclotriphosphates M^II(NH₄)₄(P₃O₉)₂x4H₂O (M ^II=Cu, Ni and Co), between 25 and 1400°C, by X-ray diffraction, thermal analyses (TG and DTA) and infrared spectrometry. This study shows that the series of the compounds M^II(NH₄)₄(P₃O₉)₂x4H₂O (M ^II=Cu, Ni and Co) after elimination of water, in two different stages, and ammonia leads, at 400°C to cyclotetraphosphate M₂ ^IIP₄O₁₂ crystallized and to a thermal residue with a formula H₄P₄O₁₂ which undergoes under a thermal degradation by evolving water and pentoxide phosphorus. The kinetic characteristics of the dehydration and elimination of ammonia have been determinated. The vibrational spectra of Cu(NH₄)₄(P₃O₉)₂x4H₂O were examined and interpreted, in the domain of the valency frequencies, on the basis of the crystalline structure of its isotypic compound Co(NH₄)₄(P₃O₉)₂x4H₂O whose cycle has the site symmetry C₁, of our results of the calculation of the IR frequencies and the successive isotopic substitutions of the equivalent atoms (3P, 3Oi and 6Oe belonging to the P₃Oi₃Oe₆ ring) of the P₃O₉ ³⁻ cycle with high symmetry D_3h. This revised version was published online in August 2006 with corrections to the Cover Date.     

Expanding the Averievite Family, (MX)Cu5O2(T5+O4)2 (T5+ = P,V; M = K,Rb, Cs,Cu; X = Cl,Br): Synthesis and Single-Crystal X-ray Diffraction Study

Averievite-type compounds with the general formula (MX)[Cu₅O₂(TO₄)], where M = alkali metal, X = halogen and T = P, V, have been synthesized by crystallization from gases and structurally characterized for six different compositions: 1 (M = Cs; X = Cl; T = P), 2 (M = Cs; X = Cl; T = V), 3 (M = Rb; X = Cl; T = P), 4 (M = K; X = Br; T = P), 5 (M = K; X = Cl; T = P) and 6 (M = Cu; X = Cl; T = V). The crystal structures of the compounds are based upon the same structural unit, the layer consisting of a kagome lattice of Cu²⁺ ions and are composed from corner-sharing (OCu₄) anion-centered tetrahedra. Each tetrahedron shares common corners with three neighboring tetrahedra, forming hexagonal rings, linked into the two-dimensional [O₂Cu₅]⁶⁺ sheets parallel to (001). The layers are interlinked by (T⁵⁺O₄) tetrahedra (T⁵⁺ = V, P) attached to the bases of the oxocentered tetrahedra in a “face-to-face” manner. The resulting electroneutral 3D framework {[O₂Cu₅](T⁵⁺O₄)₂}⁰ possesses channels occupied by monovalent metal cations M⁺ and halide ions X⁻. The halide ions are located at the centers of the hexagonal rings of the kagome nets, whereas the metal cations are in the interlayer space. There are at least four different structure types of the averievite-type compounds: the P-3m1 archetype, the 2 × 2 × 1 superstructure with the P-3 space group, the monoclinically distorted 1 × 1 × 2 superstructure with the C2/c symmetry and the low-temperature P2₁/c superstructure with a doubled unit cell relative to the high-temperature archetype. The formation of a particular structure type is controlled by the interplay of the chemical composition and temperature. Changing the chemical composition may lead to modification of the structure type, which opens up the possibility to tune the geometrical parameters of the kagome net of Cu²⁺ ions.     

Thermal properties of [MII(phen)3]2V4O12·phen·22H2O (M II=Co,Ni, Cu,phen=1,10-phenanthroline)

Thermal decomposition of three tetravanadates, [M^II(phen)₃]₂V₄O₁₂·phen·22H₂O, where M ^II is Co (1), Ni (2), Cu (3) and phen is 1,10-phenanthroline, was studied by dynamic method (for 1 and 2) or isothermally (for 3). The thermal decomposition of the studied compounds is a multi-step process which involve: discontinuous dehydration, release of uncoordinated, and of coordinated phenanthroline molecules. In course of the latter process, a phase transition of the cyclo-tetravanadates to polymeric metavanadates occurred. Metavanadates with chain structure of the anion were the final decomposition products of all tetravanadates studied. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis and structural investigation of a new cadmium cyclohexaphosphate Cd[3,4-(CH3)2C6H5NH3]4P6O18·6H2O

Single crystals of a new cyclohexaphosphate, are synthesised and investigated by X-ray diffraction. This compound crystallizes in the triclinic system with the space group P-1 and cell parameters a=7.773(4), b=9.238(3), c=18.532(7) Å, α=88.57(3), β=88.10(4), γ=67.35(4)°, Z=1 and V=1227(1) ų. The three-dimensional network is built up from parallel (0 0 1) layers of [CdP₆O₁₈(H₂O)₆]⁴⁻ between which the organic molecules are inserted. The Cd atoms, in 1(a) sites, adopt an octahedral coordination. The 3,4-xylidinium cations exercise an electrostatic interaction on the inorganic anion and establish strong H-bonds with their oxygen atoms.     

Preparation,thermal and vibrational studies of [UO2(acac-o-phdn)(L)] (L=H2O,py, DMF and Et3N)

Four new dioxouranium(VI) complexes, [UO₂(acac-o-phdn)(L)] where L?=?H₂O, py, DMF and Et₃N, with the tetradentate dibasic Schiff base (acac-o-phdn), derived from condensation of acetylacetone with o-phenylene diamine have been synthesized. The infrared spectra were obtained and full assignments of all the observed vibrations are proposed on the basis of C_2v symmetry for H₂O and py complexes and C_s for the other two complexes, respectively. The bond stretching force constant and bond length of the U=O bond for the four complexes were calculated. Differential thermal analysis (DTA) and thermogravimetric (TG) analysis of the complexes were also carried out.     

Electron density investigation of a push-pull ethylene (C14H24N2O2.H2O) by X-ray diffraction at T = 21 K

The electron charge distribution in a strongly twisted push-pull ethylene [PPE, 3-(1,3-diisopropyl-2-imidazolidinylidene)-2,4-pentanedione] has been determined by low temperature (T = 21 K) single-crystal X-ray diffraction analysis. The derived electronic properties are consistent with a zwitterionic molecule, as indicated by a charge transfer of 0.82(16) e from the push to the pull moieties and a charge polarization of 0.29(7) e on the olefinic bond. A dipole moment of 12(3) D has been determined, which compares well with ab initio theoretical results in terms of both modulus and orientation. The second moments, which have also been obtained with good precision, characterize PPE as a highly quadrupolar molecule. The special electronic features of the molecule confer particular topological properties to the electron density distribution, as evidenced by comparison with "standard" organic molecules. The crystallographic asymmetric unit of the present system includes one water molecule, which is hydrogen bonded to PPE. Its topological properties have also been investigated, together with an analysis of the hydrogen bonds involved.     

Syntheses and Structures of Na2Mg3(OH)2(SO4)3·4H2O and K2Mg3(OH)2(SO4)3·2H2O

The crystal structures of Na₂Mg₃(OH)₂(SO₄)₃ · 4H₂O and K₂Mg₃(OH)₂(SO₄)₃ · 2H₂O, were determined from conventional laboratory X‐ray powder diffraction data. Synthesis and crystal growth were made by mixing alkali metal sulfate, magnesium sulfate hydrate, and magnesium oxide with small amounts of water followed by heating at 150 °C. The compounds crystallize in space group Cmc2₁ (No. 36) with lattice parameters of a = 19.7351(3), b = 7.2228(2), c = 10.0285(2) Å for the sodium and a = 17.9427(2), b = 7.5184(1), c = 9.7945(1) Å for the potassium sample. The crystal structure consists of a linked MgO₆–SO₄ layered network, where the space between the layers is filled with either potassium (K⁺) or Na⁺‐2H₂O units. The potassium‐bearing structure is isostructural to K₂Co₃(OH)₂(SO₄)₃ · 2(H₂O). The sodium compound has a similar crystal structure, where the bigger potassium ion is replaced by sodium ions and twice as many water molecules. Geometry optimization of the hydrogen positions were made with an empirical energy code.     

Jahn-Teller-Verzerrungen von Übergangsmetallionen in tetraedrischer Koordination – die Strukturen von Cat[MII(NCS)4] (MII: Co,Ni, Cu) und von Spinellmischkristallen MIICr2O4(MII: Zn?Ni,Zn?Cu,Cu?Ni)

Jahn-Teller Distortions of Transition Metal Ions in Tetrahedral Coordination — The Structures of Cat[M^II(NCS)₄]^II (M^II: Co, Ni, Cu) and of Mixed Crystals M^IICr₂O₄(M^II: Zn? Ni, Zn? Cu, Cu? Ni) of the Spinel Type The structure determination of compounds Cat[M^II(NCS)₄] with Cat = p-xylylenebis(triphenylphosphonium)²⁺ and M^II = Co, Ni, Cu [space group P2₁/n, Z = 4] yielded pseudotetrahedral M^IIN₄-polyhedra, which are distorted by packing forces and vibronic coupling effects of the Jahn-Teller type. Spinel mixed crystals with M^II = Zn? Ni, Zn? Cu, Ni? Cu in the tetrahedral sites exhibit phase transition to tetragonal and o-rhombic structures, induced by cooperative Jahn-Teller interactions. The distortion symmetries of the M^IIN₄ and M^IIO₄ tetrahedra are analysed on the basis of the respective electronic groundstate and the possible Jahn-Teller active vibrational modes.     

Synthesis and X-ray diffraction study of nanostructured particles of cuprate manganites LaM 2 II CuMnO6 (MII = Mg,Ca, Sr,Ba)

Cuprate manganites of the composition LaM ₂ ^II CuMnO₆ (M^II = Mg, Ca, Sr, Ba) were synthesized from lanthanum, copper(II), and manganese(III) oxides and alkaline-earth metal carbonates by high-temperature solid-phase synthesis. By grinding the produced substances in a ball mill, their nanostructured particles were obtained, the sizes of which were determined with an electron microscope. Indexing the X-ray powder diffraction patterns of the cuprate manganites established that all of them crystallize in the cubic system with the following unit cell parameters: LaMg₂CuMnO₆: a = 15.523 ± 0.033 Å, Z = 6, V ⁰ = 3740.48 ± 0.10 ų, V _el.cell ⁰ = 623.41 ± 0.03ų, ρ_X-ray = 5.81 g/cm³, and ρ_pycn = 5.75 ± 0.06 g/cm³; LaCa₂CuMnO₆: a = 15.422 ± 0.058 Å, Z = 4, V ⁰ = 3667.94 ± 0.174 ų, V _el.cell ⁰ = 916.48 ± 0.04 ų, ρ_X-ray = 3.77 g/cm³, and ρ_pycn = 3.72 ± 0.05 g/cm³; LaSr₂CuMnO₆: a = 15.275 ± 0.049 Å, Z = 4, V ⁰ = 3564.05 ± 0.27 ų, V _el.cell ⁰ = 891.01 ± 0.07 ų, ρ_X-ray = 4.31 g/cm³, and ρ_pycn = 4.25 ± 0.05 g/cm³; and LaBa₂CuMnO₆: a = 15.589 ± 0.029 Å, Z = 4, V ⁰ = 3788.39 ± 0.09 ų, V _el.cell ⁰ = 947.10 ± 0.02 ų, ρ_X-ray = 4.74 g/cm³, and ρ_pycn = 4.70 ± 0.05 g/cm³. The data of an IR spectroscopic study of the cuprate manganites were presented.     

Light-induced structural changes in (HgBr2)3(As4S4)2: An X-ray single-crystal diffraction,Raman spectroscopy and ab initio study

To investigate the behaviour of the As₄S₄ molecule within a crystal-chemical environment differing from realgar, α-As₄S₄, and its high-temperature polymorph, β-As₄S₄, the effects of the light exposure on the structure of the (HgBr₂)₃(As₄S₄)₂ adduct have been studied. Differently from the cases previously studied, the action of the light filtered using a 550 nm long-wavelength pass filter did not produce any evident effect on the unit-cell. On the other hand, employing the 440 nm long-wavelength pass filter, remarkable variations of the unit-cell parameters were observed. In particular, an increase of the a, c, and β, and a decrease of the b parameter, producing on the whole an expansion of the unit-cell volume, is observed as a function of the light exposure times. Structure refinements indicated that the increase of the unit-cell volume is to ascribe to the formation of an increasing fraction (up to 20%) of pararealgar-type replacing the realgar-type molecule. Further light-exposure did not cause any further increase of the lattice parameters. On the contrary, a decrease of the unit-cell volume occurred by keeping the crystal in the dark (46 days): due to the loss of the crystallinity, only the core of the crystal, less altered and with smaller unit-cell volume, contributes to the diffraction effects. Micro-Raman spectra were collected on crystals exposed to the above mentioned wavelength light for increasing times. The peak at 275(±1) cm⁻¹ whose intensity increases as a function of the exposure time confirms the transition from a realgar- to a pararealgar-type molecule in the (HgBr₂)₃(As₄S₄)₂ adduct. Relativistic DFT-GGA ab initio band structure calculations reveal a direct band gap of 2.04 eV and quite flat valence and conduction bands around the Fermi level. According to analyses of the atomic orbital contributions to the electronic band structures the highest occupied states are attributed to non-bonding p-states of As.     

Syntheses and crystal structures of heterometallic complexes [{Cu(en)2}2{Cu(en)2(NH3)}{M4Te4(CN)12}]·5H2O (M = Mo,W)

Evaporation of aqueous ammonia solutions of K₇[Mo₄Te₄(CN)₁₂]·12H₂O or K₆[W₄Te₄(CN)₁₂]·5H₂O, copper(ii) chloride, and ethylenediamine afforded the isostructural heterometallic complexes [{Cu(en)₂}₂{Cu(en)₂(NH₃)}{M₄Te₄(CN)₁₂}]·5H₂O (M = Mo or W), which were characterized by IR and ESR spectroscopy and X-ray diffraction analysis.     

Syntheses and Crystal Structures of （S）-Methyl 2-（4-R-phenylsulfonamido）-3-（1H-indol-3-yl）propanoate （R = H （1） and Cl （2））

The title compounds （S）-methyl-2-（4-R-phenylsulfonamido）-3-（1H-indol-3- yl）propanoate （R = H （1）, Cl （2）） have been synthesized and their crystal structures also have been determined by X-ray single-crystal diffraction. Compound 1 （C18H18N2O4S） belongs to orthorhombic, space group P212121 with a = 9.6348（14）, b = 11.1517（17）, c = 16.412（3） A, V = 1763.4（5） A^3, Mr = 358.40, Z = 4, De = 1.350 g/cm^3,/t = 0.209 mm^-1, F（000） = 752, R = 0.0348 and wR = 0.0714. Compound 2 （CI8H17ClN2O4S） crystallizes in orthorhombic, space group P212121 with a = 9.3128（14）, b = 10.9655（16）, c = 17.783（3） A, V = 1815.9（5） A^3, Mr = 392.85, Z = 4, De = 1.437 g/cm^3, p = 0.352 mm^-1, F（000） = 816, R = 0.0389 and wR = 0.0845. The absolute structure Flack parameters X of compounds 1 and 2 are -0.03（8） and -0.06（7）, respectively. X-ray analysis reveals that the crystal structures of these two compounds both involve two intermolecular N-H…O hydrogen bond＇s.     

Synthesis,Crystal Structure,and NMR Spectroscopy of a New P-Phenylenediamonium Diphosphate [p-NH3C6H4NH3]H2P2O7

Crystal growth and characterization by X-ray diffraction and NMR spectroscopy of a new p-phenylenediamonium diphosphate [p-NH₃ C ₆ H ₄ NH ₃]H ₂ P ₂ O ₇ are reported. This compound crystallizes in a triclinic unit cell P1 with the parameters a = 7.130(3), b = 9.047(3), c = 9.350(2) Å, α = 133.44(2)°, β = 95.02(2)°, γ = 107.11(4)°, Z = 2, V = 514.3(15) ų, and D _x = 1.848 g.cm^{? 3}. The crystal structure has been solved and refined to R = 0.0273, using 3678 independent reflections. The atomic arrangement is build up by infinite ribbons of [H₂ P ₂ O ₇] ^2? anions, extending along the a-direction at y = 1/2. Between these ribbons are located the p-phenylenediammonium entities, which form hydrogen bonds N─H…O with some external oxygen atoms of phosphoric groups. Crystallographic results are correlated with that of the solid state ¹³C and ³¹P MAS NMR spectroscopy.     

Formation of solid solution and its effect on lithium insertion schemes for advanced lithium-ion batteries: X-ray absorption spectroscopy and X-ray diffraction of LiCoO2, LiCo1/2Ni1/2O2 and LiNiO2

The X-ray absorption spectra (XAS) of LiCoO₂, LiCo_1/2Ni_1/2O₂ and LiNiO₂ were examined together with X-ray diffraction (XRD). Co and Ni K-edge XANES spectra of LiCo_1/2Ni_1/2O₂ are quite similar to that of LiCoO₂ or LiNiO₂, suggesting that electronic states of Co and Ni in LiCo_1/2Ni_1/2O₂ are Co³⁺ and Ni³⁺. Analytical results of Co and Ni K-edge EXAFS oscillations on the first coordination shell of nickel and cobalt ions in LiCo_1/2Ni_1/2O₂ indicate that the local environment around the targeted species is the same as that in LiCoO₂ or LiNiO₂. Since there is no doubt about the crystal and electronic structures of LiCoO₂ and LiNiO₂, the results indicate that LiCo_1/2Ni_1/2O₂ consists of low-spin states of Co³⁺ and Ni³⁺ distributed at equivalent positions in triangular lattice of sites forming homogeneous transition metal oxide layers. Thus, XAS complements XRD in describing solid solution LiCo_1/2Ni_1/2O₂ of LiCoO₂ and LiNiO₂. The electrochemical behaviors of LiCoO₂, LiCo_1/2Ni_1/2O₂ and LiNiO₂ are also restated and the effects of the formation of solid solution on the change in lattice dimension during topotactic electrochemical reactions are discussed.