DSC study of the phase transitions in [Ni(D2O)6](ClO4)2 and [Ni(H2O)6](ClO4)2

DSC measurements were carried out for [Ni(H₂O)₆](ClO₄)₂ (sampleH) and [Ni(D₂O)₆](ClO₄)₂ (sampleD) in the temperature range 300–380 K. For both compounds two anomalies on the DSC curves were detected. The results for sampleH are compared to those previously obtained using adiabatic calorimetry method. For both compounds studied in this work the high-temperature transition appears at the same temperature while the low-temperature one is shifted towards higher temperatures in sampleD. Disorder connected with H₂O or D₂O groups is suggested in the intermediate phase between the low- and high-temperature transitions.     

Thermal and calorimetric studies of M(IO3)2·6H2O and M(IO3)2·6D2O forM 2+=Ca2+ and Sr2+

Thermal and calorimetric studies were carried out on M(IO₃)₂·6H₂O and M(IO₃)₂·6D₂O forM ²⁺=Ca²⁺ and Sr²⁺, using DTA and DSC methods. The thermal behaviour of the ordinary and deuterated hydrates is outlined and the differences observed between them are discussed. The enthalpies of the phase transitions were determined. The H _f ^o for Ca(IO₃)₂·6H₂O, Ca(IO₃)₂·6H₂O(D₂O) and Sr(IO₃)₂·6H₂O(D₂O) were calculated from the H _deh data and comments are made on the isotope effect observed.

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Zusammenfassung Mittels DTA- und DSC-Methoden wurden Me(IO₃)₂·6H₂O und Me(IO₃)₂·6D₂O (mitMe ²⁺=Ca²⁺ und Sr²⁺) thermisch und kalorimetrisch untersucht. Es wird ein Überblick über das thermische Verhalten ordentlicher und deuterierter Hydrate gegeben, in dem auch die Unterschiede zwischen beiden diskutiert werden. Die Enthalpien der untersuchten Phasenumwandlungen wurden bestimmt. Aus den Daten für H_deh wurde H_f von Ca(IO₃)₂·6H₂O, Ca(IO₃)₂H₂O(D₂O) und Sr(IO₃)₂·6H₂O(D₂O) berechnet und Bemerkungen zum beobachteten Isotopeneffektes gemacht.

     

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.     

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.     

Studies on synthesis, characterization and thermochemistry of Mg2[B2O4(OH)2]·H2O

A new magnesium borate Mg₂[B₂O₄(OH)₂]·H₂O has been synthesized by the method of phase transformation of double salt at hydrothermal condition and characterized by XRD, IR, TG and DSC. The enthalpy of solution of Mg₂[B₂O₄(OH)₂]·H₂O in 0.9764 mol L^–1 HCl was determined. With the incorporation of the enthalpies of solution of H₃BO₃ in HCl (aq), of MgO in (HCl+H₃BO₃) (aq), and the standard molar enthalpies of formation of MgO(s), H₃BO₃(s), and H₂O(l), the standard molar enthalpy of formation of –(3185.78±1.91) kJ mol^–1 of Mg₂[B₂O₄(OH)₂]·H₂O was obtained.This revised version was published online in November 2005 with corrections to the Cover Date.     

Efficient synthesis of mono- and disubstituted 2,3-dihydroquinazolin-4(1H)-ones using KAl(SO4)2·12H2O as a reusable catalyst in water and ethanol

KAl(SO₄)₂·12H₂O was found to catalyze efficiently a one-pot three-component cyclocondensation of isatoic anhydride and primary amines or ammonia sources such as (NH₄)₂CO₃, NH₄OAc and NH₄Cl with aromatic aldehydes under mild conditions to afford the corresponding mono- and disubstituted 2,3-dihydroquinazolin-4(1H)-ones in good yields.     

H2O−D2O solvent isotope effect in the volume behavior of some high-charge high-size electrolytes

The apparent molar volumes V of KCl, BaCl₂, K₂SO₄, LaCl₃, Co(en)₃Cl₃ [Tris(ethylenediamine)cobalt(III) chloride], K₃Co(CN)₆, K₃Fe(CN)₆, K₄Fe(CN)₆, and Ba₃[Co(CN)₆]₂ have been determined at 25°C in both light and heavy water. The V values in D₂O are systematically lower and increase more rapidly with salt concentration than the V in H₂O. The volume of transfer from H₂O to D₂O as well as the partial molar volume at infinite dilution in both solvents have also been calculated. These results together with literature values for other electrolytes were used to estimate both of these quantities for D₂O solutions of individual ions. The predictions of ion hydration models and ion-ion interactions are compared with experimental observations.     

Hydrothermal synthesis, characterization and thermochemistry of Ca2[B2O4(OH)2]·0.5H2O

A pure calcium borate Ca₂[B₂O₄(OH)₂]·0.5H₂O has been synthesized under hydrothermal condition and characterized by XRD, FT-IR and TG as well as by chemical analysis. The molar enthalpy of solution of Ca₂[B₂O₄(OH)₂]·0.5H₂O in HC1·54.582H₂O was determined. From a combination of this result with measured enthalpies of solution of H₃BO₃ in HC1·54.561H₂O and of CaO in (HCl + H₃BO₃) solution, together with the standard molar enthalpies of formation of CaO(s), H₃BO₃(s) and H₂O(l), the standard molar enthalpy of formation of −(3172.5 ± 2.5) kJ mol⁻¹ of Ca₂[B₂O₄(OH)₂]·0.5H₂O was obtained.     

外偶极电场作用下H_2O,D_2O和T_2O的可逆分解电压

采用密度泛函B3P86方法和6-311++G(3df,3pf)基组,计算了在-0.05～0.05a.u.外偶极电场作用下,H2O,D2O,T2O,H2,D2,T2,O2的电子能量、核运动能量和熵值,在此基础上通过计算H2O(g)→H2(g)+O2(g)、D2O(g)→D2(g)+O2(g)、T2O(g)→T2(g)+O2(g)的焓变ΔH、熵变ΔS、Gibbs函数变化ΔG,最后得到了H2O,D2O,T2O的可逆分解电压Er.计算结果表明,外偶极电场存在时,H2O,D2O,T2O的Gibbs自由能变ΔG和可逆分解电压Er都有明显的变化,当外偶极电场正方向增加时,其Gibbs自由能变ΔG和可逆分解电压Er均趋于线性增加;当外偶极电场负方向增加时,其Gibbs自由能变ΔG和可逆分解电压Er均趋于线性减小;在相同外偶极电场作用下,Gibbs自由能变ΔG和可逆分解电压Er随H2O,D2O,T2O依次增加.     

Transition metal tetramolybdate dihydrates MMo4O13·2H2O (M=Co,Ni) having a novel pillared layer structure

Hydrothermal synthesis in the M/Mo/O (M=Co,Ni) system was investigated. Novel transition metal tetramolybdate dihydrates MMo₄O₁₃·2H₂O (M=Co,Ni), having an interesting pillared layer structure, were found. The molybdates crystallize in the triclinic system with space group P−1, Z=1 with unit cell parameters of a=5.525(3) Å, b=7.058(4) Å, c=7.551(5) Å, α=90.019(10)°, β=105.230(10)°, γ=90.286(10)° for CoMo₄O₁₃·2H₂O, and a=5.508(2) Å, b=7.017(3) Å, c=7.533(3) Å, α=90.152(6)°, β=105.216(6)°, γ=90.161(6)° for NiMo₄O₁₃·2H₂O The structure is composed of two-dimensional molybdenum-oxide (2D Mo-O) sheets pillared with CoO₆ octahedra. The 2D Mo-O sheet is made up of infinite straight ribbons built up by corner-sharing of four molybdenum octahedra (two MoO₆ and two MoO₅OH₂) sharing edges. These infinite ribbons are similar to the straight ones in triclinic-K₂Mo₄O₁₃ having 1D chain structure, but are linked one after another by corner-sharing to form a 2D sheet structure, like the twisted ribbons in BaMo₄O₁₃·2H₂O (or in orthorhombic-K₂Mo₄O₁₃) are.     

H2O + Fe(NO3)3 + Ni(NO3)2 ternary system isotherms at 0 °C and 30 °C

H₂O + Ni(NO₃)₂ binary system were investigated in the temperature range from −25 °C to 55 °C. The solid-liquid equilibria of the ternary system H₂O + Fe(NO₃)₃ + Ni(NO₃)₂ were studied using a synthetic method based on conductivity measurements. Tow isotherms were established at 0 °C and 30 °C, and the appearing stable solid phases are iron nitrate nonahydrate (Fe(NO₃)₃·9H₂O), iron nitrate hexahydrate (Fe(NO₃)₃·6H₂O), nickel nitrate hexahydrate (Ni(NO₃)₂·6H₂O) and nickel nitrate tetrahydrate (Ni(NO₃)₂·4H₂O).     

Two Ce(SO4)2·4H2O polymorphs: Crystal structure and thermal behavior

Syntheses, crystal structures and thermal behavior of two polymorphic forms of Ce(SO₄)₂·4H₂O are reported. The first modification, α-Ce(SO₄)₂·4H₂O (I), crystallizes in the orthorhombic space group Fddd, with a=5.6587(1), b=12.0469(2), c=26.7201(3) Å and Z=8. The second modification, β-Ce(SO₄)₂·4H₂O (II), crystallizes in the orthorhombic space group Pnma, with a=14.6019(2), b=11.0546(2), c=5.6340(1) Å and Z=4. In both structures, the cerium atoms have eight ligands: four water molecules and four sulfate groups. The mutual position of the ligands differs in (I) and (II), resulting in geometrical isomerism. Both these structures are built up by layers of Ce(H₂O)₄(SO₄)₂ held together by a hydrogen bonding network. The dehydration of Ce(SO₄)₂·4H₂O is a two step (I) and one step (II) process, respectively, forming Ce(SO₄)₂ in both cases. During the decomposition of the anhydrous form, Ce(SO₄)₂, into the final product CeO₂, intermediate xCeO₂·yCe(SO₄)₂ species are formed.     

Infrared spectra (700–200 cm−1) and6Li/7Li and H2O/D2O isotope effects for four isotopically substituted lithium formate monohydrates

The infrared spectra, in the 700–200 cm^–1 region, have been reported for⁶LiHCO₂ · H₂O,⁶LiHCO₂ · D₂O,⁷LiHCO₂ · H₂O and⁷LiHCO₂ · D₂O and the observed fundamental bands have been discussed taking into account the⁶Li/⁷Li and H₂O/D₂O isotope wavenumber shifts on the fundamental vibrations.

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Infrarotspektren (700–200 cm^–1) und⁶Li/⁷Li- und H₂O/D₂O-Isotopeneffekte für vier isotopensubstituierte Lithiumformat-monohydrate

Zusammenfassung Die Infrarotspektren in der Region von 700–200 cm^–1 werden für⁶LiHCO₂ · H₂O,⁶LiHCO₂ · D₂O,⁷LiHCO₂ · H₂O und⁷LiHCO₂ · D₂O angegeben und die beobachteten Grundschwingungen zusammen mit den isotopischen Verschiebungen der Wellenzahlen diskutiert.

     

Etude de l’isotherme 25°C du système quasi quaternaire H2O-Zn(NO3)2·6H2O-Cu(NO3)2·3H2O-NH4NO3;I- Isoplèthes 4 masse% NH4NO3, 8 ma

The solid-liquid equilibria of the quasi-quaternary system H₂O-Zn(NO₃)₂·6H₂O-Cu(NO₃)₂·3H₂O-NH₄NO₃ were studied at 25°C by using a synthetic method based on conductivity measurements. Three isoplethic sections has been established at 25°C and the stable solid phases which appear are: NH₄NO₃(IV), Zn(NO₃)₂·6H₂O, anhydrous Cu(NO₃)₂, Cu(NO₃)₂·3H₂O and metastable Cu(NO₃)·2.5H₂O. Neither double salts, nor mixed crystals are observed at these temperatures and composition range.     

Tetranuclear Pt<Subscript>2</Subscript>Cu<Subscript>2</Subscript> Complex with a Staircase-Shaped Chain Aggregate in the Solid State

The reaction of the tetranuclear cyanide aquo complex [{Pt(CN)₄Cu(bipy)(H₂O)}₂]· 2H₂O with aqueous ammonia produces the new tetranuclear ammino-containing product [{Pt(CN)₄Cu(bipy)(NH₃)}₂] (1), with terminal cyanide groups and with NH₃ coordinated to the Cu atom. The distorted trigonal bipyramidal coordination about copper in 1 differs from the square-pyramidal coordination present in the starting material. The bipyridine ligand in 1 is nearly perpendicular to the tetranuclear core of the molecule, as opposed to its coplanar disposition in the aquo complex. The two platinum atoms of the tetranuclear core in 1 form Pt···Pt interactions of 3. 2390(8) Å with platinum atoms of neighboring molecules, producing an echelon-shaped supramolecular chain held together by staggered (CN)₄Pt···Pt(CN)₄ linkages, an aggregate structure which does not have a precedent in chemistry derived from the Pt(CN)₄ building block.     

On the correct spin lattice for the spin-gapped magnetic solid NH4CuPO4·H2O

NH₄CuPO₄·H₂O is a spin-gapped compound that has been described in terms of an isolated antiferromagnetic spin dimer model. To explore the origin of this spin gap, we examined the spin exchange interactions of NH₄CuPO₄·H₂O by performing qualitative spin dimer analysis based on extended Hückel tight binding calculations and also by carrying out quantitative mapping analysis based on first principles density functional theory electronic band structure calculations. Our study indicates that, to a first approximation, the magnetic properties of NH₄CuPO₄·H₂O should be described by an antiferromagnetic and ferromagnetic alternating chain.     

Kinetics of the thermal decomposition of [Co(NH3)6]2(C2O4)3·4H2O

The thermal decomposition of [Co(NH₃)₆]₂(C₂O₄)₃·4H₂O was studied under isothermal conditions in flowing air and argon. Dissociation of the above complex occurs in three stages. The kinetics of the particular stages thermal decomposition have been evaluated. The R_N and/or A_M models were selected as those best fitting the experimental TG curves. The activation energies,E, and lnA were calculated with a conventional procedure and by a new method suggested by Kogaet al. [10, 11]. Comparison of the results have showed that the Arrhenius parameters values estimated by the use of both methods are very close. The calculated activation energies were in air: 96 kJ mol^–1 (R_1.575, stage I); 101 kJ mol^–1 (Ain1.725 stage II); 185 kJ mol^–1 (A _2.9, stage III) and in argon: 66 kJ mol^–1 (A _1.25, stage I); 87 kJ mol^–1 (A _1.825, stage II); 133 kJ mol^–1 (A _2.525, stage III).     

配位化合物Zn(Met)3(NO3)2·H2O(s)(Met=L-α-蛋氨酸)的低温热容及标准摩尔生成焓

利用精密绝热热量仪测定了化合物配合物Zn(Met)₃(NO₃)₂·H₂O (s) (Met=L-α-蛋氨酸)在78-371 K温区的摩尔热容. 通过热容曲线解析, 得到了该配合物的起始脱水温度为T_D=325.10 K. 将该温区的摩尔热容实验值用最小二乘法拟合得到了摩尔热容(C_p)对约化温度(T)的多项式方程, 由此计算得到了配合物的舒平热容值和热力学函数值. 基于设计的热化学循环, 选择100 mL of 2 mol·L^-1 HCl为量热溶剂, 利用等温环境溶解-反应热量计, 得到了298.15 K配合物的标准摩尔生成焓为Δ_fH_m⁰[Zn(Met)₃(NO₃)₂·H₂O(s),s]=-(1472.65±0.76) J·mol^-1.     

Investigation on The Thermal Properties of Fe2O(SO4)2. Part II

Fe₂O(SO₄)₂ is a secondary product of the decomposition of FeSO₄⋅H₂O. Part I of this study presents results on the synthesis of Fe₂O(SO₄)₂ in gaseous environment containing either low or high concentration of oxygen. In this paper the existence of differences between the structures of Fe₂O(SO₄)₂ and Fe₂(SO₄)₃ is proved on the basis of a detailed thermal study of Fe₂O(SO₄)₂ upon dynamic heating (differential thermal analysis) and upon isothermal heating (thermal-analytic balance) in various gaseous environments as well as by presenting kinetic data on the processes of decomposition of both compounds. This revised version was published online in July 2006 with corrections to the Cover Date.     

NMR relaxation study of the phase transitions and relaxation mechanisms of the alums MCr(SO4)2·12H2O (M=Rb and Cs) single crystals

The physical properties and phase transition mechanisms of MCr(SO₄)₂·12H₂O (M=Rb and Cs) single crystals have been investigated. The phase transition temperatures, NMR spectra, and the spin-lattice relaxation times T₁ of the ⁸⁷Rb and ¹³³Cs nuclei in the two crystals were determined using DSC and FT NMR spectroscopy. The resonance lines and relaxation times of the ⁸⁷Rb and ¹³³Cs nuclei undergo significant changes at the phase transition temperatures. The sudden changes in the splitting of the Rb and Cs resonance lines are attributed to changes in the local symmetry of their sites, and the changes in the temperature dependences of T₁ are related to variations in the symmetry of the octahedra of water molecules surrounding Rb⁺ and Cs⁺. We also compared these ⁸⁷Rb and ¹³³Cs NMR results with those obtained for the trivalent cations Cr and Al in MCr(SO₄)₂·12H₂O and MAl(SO₄)₂·12H₂O crystals.