Calorimetric study and thermal analysis of [Gd4/3Y2/3(Gly)6(H2O)4](ClO4)6·5H2O and [ErY(Gly)6(H2O)4](ClO4)6·5H2O (Gly: glycin)

Two solid-state coordination compounds of rare earth metals with glycin, [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O and [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O were synthesized. The low-temperature heat capacities of the two coordination compounds were measured with an adiabatic calorimeter over the temperature range from 78 to 376 K. [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O melted at 342.90 K, while [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O melted at 328.79 K. The molar enthalpy and entropy of fusion for the two coordination compounds were determined to be 18.48 kJ mol⁻¹ and 53.9 J K⁻¹ mol⁻¹ for [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O, 1.82 kJ mol⁻¹ and 5.5 J K⁻¹ mol⁻¹ for [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O, respectively. Thermal decompositions of the two coordination compounds were studied through the thermogravimetry (TG). Possible mechanisms of the decompositions are discussed.     

Vibrational spectra of α-Ge(HPO4)2·H2O compound

We have measured Raman and infrared spectra of α-Ge(HPO₄)₂·H₂O compound at room temperature. The analysis of vibrational modes indicated the presence of two non-equivalent HPO₄²⁻ units in agreement with ³¹P nuclear magnetic resonance measurements. A tentative assignment of all the observed modes is proposed based on the previous works reported for other hydrogenphosphate-based compounds.     

Structure of Ba Na Ethylenediaminetetraacetatocobaltate(III) Perchlorate, Na[Ba6(H2O)25][Co(Edta)]4(ClO4)9 · 5H2O

Crystals with uncommon composition NaBa₆[Co(Edta)]₄(ClO₄)₉ · 30H₂O (Edta⁴⁻ is ethylenediaminetetraacetic acid anion) were obtained with the following unit cell parameters: a = 14.8513(9) Å, b = 26.2361(15) Å, c = 15.1789(9) Å, α = 91.661(7)°, β = 113.035(7)°, γ = 89.897(7)°, space group P1¯. Each complex anion [Co(Edta)]⁻ is bonded through the carboxyl O atoms to five Ba atoms to give three-dimensional framework in a crystal. One perchlorate ion forms Ba-O-Cl-O-Ba bridge between the Ba atoms; four ClO ₄ ⁻ ions are isolated, while the remaining four ions act as monodentate ligands at the Ba atoms. The water molecules (25 in sum) complete the coordination sphere of the Ba atoms to eight-, nine-, or ten-vertex polyhedron. Four water molecules are in the closest surrounding of the Na atom, one H₂O molecule is isolated.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 8, 2005, pp. 590–595.Original Russian Text Copyright © 2005 by Zabel, Poznyak, Pawlowski.     

Photoacoustic spectra of Nd(TFA)3 · 2H2O and Nd(HFA)3 · 2H2O

A new synthesis of trisfluoroacetylactone (TFA) and hexafluoroacetylactone (HFA) Nd complexes: Nd(TFA)₃ · 2H₂O and Hd(HFA)₃ · 2H₂O is reported. The photoacoustic (PA) spectra in the 300–800 nm region of the compounds NdCl₃ · 6H₂O, Nd(TFA)₃ · 2H₂O and Nd(HFA)₃ · 2H₂O are reported. The PA absorption bands are assigned and their relative intensities represented by intensity branching vectors are calculated. The perturbation of the ligand on the energy levels of Nd³⁺ ion is discussed and a model of the relaxation process of Nd(HFA)₃ · 2H₂O is proposed based on its PA and absorption spectra.     

[Gd2(Gly)6(H2O)4](ClO4)6(H2O)5的合成、晶体结构与热化学研究

利用微波技术合成了配合物[Gd₂(Gly)₆(H₂O)₄](ClO₄)₆(H₂O)₅, 进行了化学成分分析、红外表征和热重分析. 应用X衍射仪测定其晶体结构, 该晶体为一维链结构, 属三斜晶系, P 空间群, 晶胞参数: a＝1.1569(17) nm, b＝1.4138(2) nm, c＝1.5642(2) nm, α＝96.910(2)°, β＝102.735(2)°, γ＝105.512(2)°, V＝2.3606(6) nm³, Z＝2, D_c＝2.144 g•cm^－3. 采用精密溶解-反应量热计, 通过设计热化学循环, 计算出了该配合物的标准摩尔生成焓为 －(7960.73±3.23) kJ•mol^－1.     

A novel three-dimensional malonate-bridged complex {[Cu4(4,4′- bpy)8(mal)2(H2O)4](ClO4)2(H2O)4(CH3OH)2}n

A novel malonate-bridged copper (II) compound of formula {[Cu₄(4,4′-bpy)₈(mal)₂(H₂O)₄](ClO₄)₂(H₂O)₄(CH₃OH)₂}_n (4,4′-bpy = 4,4′-bipyridine; mal = malonate dianion) has been prepared and structurally characterized by X-ray crystallography. This compound exhibits a novel three-dimensional network being composed of Cu-4,4′-bipyridine layers which are pillared by malonate bridge ligands. The copper(II) ions has two different coordination environment.     

Isolation and characterization of a novel multibridged tetradentate dianionic form of pyridoxic acid. Crystal structure of tetranuclear [Cu4(PAA)2(Bipyam)4(H2O)2Cl2](NO3)2·CH3OH·10H2O

The X-ray analysis of the tetranuclear copper(II) complex formed from pyridoxic acid and 2,2′-dipyridylamine reveals a novel metal binding mode of pyridoxic acid as a multibridged tetradentate dianion. Here the pyridoxic acid moiety uses all possible sites except the pyridine nitrogen for metal coordination.     

Hydrothermal synthesis and structure of one-dimensional Co(dien)2(VO3)3·(H2O) (dien=diethylenetriamine)

One-dimensional Co(dien)₂(VO₃)₃·(H₂O) was prepared from the hydrothermal reaction of NH₄VO₃, Co₂O₃, diethylenetriamine (dien) and H₂O at 130 °C. The compound crystallizes in the monoclinic system, space group P2₁/c with a=16.1581(6) Å, b=8.7006(3) Å, c=13.9893(4) Å, β=103.1483(11)°, V=1915.13(11) Å³, Z=4, and R₁=0.0268 for 3060 observed reflections. Single crystal X-ray diffraction revealed that the structure is composed of infinite one-dimensional chains formed by corner-sharing VO₄ tetrahedra with Co(dien)³⁺ complex cations and crystallization water molecules occupying the interchain positions, which are held together to a three-dimensional network via extensive hydrogen-bonding interactions. The compound, with a new zig-zag conformation of metavanadate chains, is the first example of vanadium oxides incorporating trivalent transition metal coordination groups. Other characterizations by elemental analysis, IR and thermal analysis are also described.     

Single-crystal characterization of Co7(OH)6(H2O)3(C4H4O4)47H2O; A new cobalt succinate identified through high-throughput synthesis

A new form of cobalt succinate has been discovered using high-throughput methods and its structure was solved by single crystal X-ray diffraction. Co₇(C₄H₄O₄)₄(OH)₆(H₂O)₃7H₂O crystallizes in the monoclinic space group P2₁/c with cell parameters: a=7.888(2) Å, b=19.082(6) Å, c=23.630(7) Å, β=91.700(5)°, V=3555(2) Å³, R₁=0.0469. This complex structure, containing 55 crystallographically distinct non-hydrogen atoms, is compared to the previously reported nickel phase, characterized using ab initio structure solution from synchrotron powder diffraction data.     

Non-equivalent water molecules in [Ni(H2O)6](ClO4)2 and in [Ni(D2O)6](ClO4)2 in the thermogravimetric investigations

The thermal decomposition of [Ni(H₂O)₆](ClO₄)₂ and [Ni(D₂O)₆](ClO₄)₂ were studied by thermogravimetric analysis (TG) and simultaneous differential thermal analysis (SDTA) at a constant heating rate. The gaseous products of the decomposition were on-line identified by a quadrupole mass spectrometer (QMS). In both cases the process of decomposition starts at ca. 410 K and is connected with removal of water molecules in a stepwise way; at the beginning the first water molecule is lost, then the second and at higher temperature the third one. The rest of the water molecules are lost in the temperature region of ClO₄⁻ decomposition. The energy of activation of the process was calculated in both cases.     

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.     

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.     

Solvothermal synthesis, crystal structure, magnetic and luminescent properties of (H3O)6·[Co4(H2O)4(HPMIDA)2(PMIDA)2)]·2H2O

A cobalt phosphonate (H₃O)₆·[Co₄(H₂O)₄(HPMIDA)₂(PMIDA)₂)]·2H₂O, 1, has been synthesized from a mild solvothermal reaction of Co(II) ion with N-(phosphonomethyl)iminodiacetic acid (H₄PMIDA). Compound 1 crystallizes in the triclinic space group with cell parameters of , , , α=93.06(3)°, β=99.66(3)°, γ=90.34(3)° and Z=1. Compound 1 shows a novel tetra-nuclear molecular structure. In the crystal lattice, molecules of 1 hydrogen bond to each other to form two-dimensional (2D) layers, which are further linked together by the co-crystallized H₂O molecules and H₃O⁺ counter ions through hydrogen bonding to form the 3D supramolecular network. Thermogravimetric analysis, IR spectrum, magnetic susceptibility and luminescent spectra are given.     

Syntheses and X-ray crystal structures of [Co(η-CO3)(NH3)4](NO3)·0.5H2O and [(NH3)3Co(μ-OH)2(μ-CO3)Co(NH3)3][NO3]2·H2O

[Co(η²-CO₃)(NH₃)₄](NO₃)·0.5H₂O and [(NH₃)₃Co(μ-OH)₂(μ-CO₃)Co(NH₃)₃][NO₃]₂·H₂O were prepared by prolonged aerial oxidation of a solution of Co(NO₃)₂·6H₂O and ammonium carbonate in aqueous ammonia. The formation of these side products highlights the richness of the chemistry of these systems and the possibility of by products if methods are not strictly adhered to. The X-ray crystal structures of [Co(η²-CO₃)(NH₃)₄][NO₃]·0.5H₂O and [(NH₃)₃Co(μ-OH)₂(μ-CO₃)Co(NH₃)₃][NO₃]₂·H₂O reveal a monomeric octahedral cobalt center with η²-bound CO₃²⁻ in the former, while the latter consists of a dimeric array where the two cobalt centers are bridged by two OH⁻ and one μ₂-CO₃²⁻ groups with three terminal NH₃ ligands for each Co center. In both complexes extensive hydrogen bonding interactions are evident.     

CRYSTAL STRUCTURE OF A HETERONUCLEAR LANTHANIDE COMPLEX OF ERBIUM-YTTRIUM AND GLYCINE[ErY(GlY)_6(H_2O)_4](ClO_4)_65H_2O

The title complex [ErY(Gly)_6(H_2O)_4](ClO_4)_6 5H_2O has been synthesized.Its crystalstructure has been determined by X-ray diffraction method.The crystal is triclinic with space groupP1.The unit cell parameters are as follows:a=11.518(4),b=14.105(7),c=15.530(6) ,α=96.61(3),β=102.74(3),γ=105.70(3)°,V=2327.7(17) ~3,Z=2,Dc=2.091g/cm~3.The structure has been refinedto a final R of 0.0785.The crystal is an infinite chain complex,in which four carboxyl groups fromglycine molecules bridge the Er(Ⅲ)and Y(Ⅲ)ion,other two carboxyl groups bridge two adjacentEr(Ⅲ)or two Y(Ⅲ)ions.     

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.     

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.     

Thermochemical properties of Ln(Gly)4Im(ClO4)3·nH2O (Ln = Gd, Tb, Dy, Y)

The enthalpies of dissolution in water of new ternary complexes of four late trivalent lanthanide ions Ln(Gly)₄Im(ClO₄)₃·nH₂O (Ln=Gd, Tb, Dy, Y; Gly: glycine; Im: imidazole and n=1 or 2) were measured by means of a Calvet microcalorimeter. Empirical formulae for the calculation of the enthalpies of dissolution (Δ_dissH), relative apparent molar enthalpies (Δ_dissH (app)), relative partial molar enthalpies (Δ_dissH (partial)) and enthalpies of dilution (Δ_dilH_1,2) were obtained from the experimental data of the enthalpies of dissolution of these complexes. The plot of Δ_dissH_m^Θ, Δ_dissH (app) and Δ_dissH (partial) versus the values of the ionic radius of the lanthanide element (r) showed a grouping effect of the lanthanide elements, indicating that the coordinated bond between the lanthanide ions and the ligands has some covalent character. The unknown value of the standard enthalpy of dissolution for the similar complex: Ho(Gly)₄Im(ClO₄)₃·H₂O was estimated according to the plot of Δ_dissH_m^Θ versus r.     

Low-temperature heat capacity and standard enthalpy of formation of neodymium glycine perchlorate complex [Nd2(Gly)6(H2O)4](ClO4)6·5H2O

Rare-earth perchlorate complex coordinated with glycine [Nd₂(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O was synthesized and its structure was characterized by using thermogravimetric analysis (TG), differential thermal analysis (DTA), chemical analysis and elementary analysis. Its purity was 99.90%. Heat capacity measurement was carried out with a high-precision fully-automatic adiabatic calorimeter over the temperature range from 78 to 369 K. A solid-solid phase transformation peak was observed at 256.97 K, with the enthalpy and entropy of the phase transformation process are 4.438 kJ mol⁻¹ and 17.270 J K⁻¹ mol⁻¹, respectively. There is a big dehydrated peak appears at 330 K, its decomposition temperature, decomposition enthalpy and entropy are 320.606 K, 41.364 kJ mol⁻¹ and 129.018 J K⁻¹ mol⁻¹, respectively. The polynomial equations of heat capacity of this compound in different temperature ranges have been fitted. The standard enthalpy of formation was determined to be −8023.002 kJ mol⁻¹ with isoperibol reaction calorimeter at 298.15 K.     

IR and Raman spectra of two layered aluminium phosphates Co(en)3Al3P4O16 · 3H2O and [NH4]3[Co(NH3)6]3[Al2(PO4)4]2 · 2H2O

The FT IR and FT Raman spectra of Co(en)₃Al₃P₄O₁₆ · 3H₂O (compound I) and [NH₄]₃[Co(NH₃)₆]₃[Al₂(PO₄)₄]₂ · 2H₂O (compound II) are recorded and analysed based on the vibrations of Co(en)₃³⁺, Co(NH₃)₆³⁺, NH₄⁺, Al---O---P, PO₃, PO₂ and H₂O. The observed splitting of bands indicate that the site symmetry and correlation field effects are appreciable in both the compounds. In compound I, the overtone of CH₂ deformation Fermi resonates with its symmetric stretching vibration. The NH₄ ion in compound II is not free to rotate in the crystalline lattice. Hydrogen bonding of different groups is also discussed.