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Abstract  

Sulphur substitution of oxygen in LiMn2O4 spinel destroyed the ideal symmetry of MnO6 octahedrons. In consequence, the phase change at about room temperature is strongly retarded, manifested by lowering heat of the transition and hysteresis of the temperature dependence of electrical conductivity. The optimal conditions for preparation of sulphur substituted spinel LiMn2O4–ySy have been determined.

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Abstract  

A new method for the possible incorporation of nuclear wastes has been attempted here by using ceramic matrix of TiO2 as a host precursor for confinement. Hafnium is used as a simulant for actinide high-level waste. After incorporating 181Hf tracer into TiO2 matrix, the leaching property of the resulting matrix was studied in water, sodium chloride and humic acid solutions. The leaching was measured in each of the case by following the radioactivity of 181Hf. TiO2 matrix has also been exposed to γ-radiation in order to simulate the radiation field for nuclear waste. It has been investigated with a nuclear technique called time differential perturbed Angular Correlation (TDPAC) that the lattice structure of titania remains undisturbed even under a strong radiation field. The leaching of 181Hf has also been studied after irradiating the TiO2 matrix with γ-radiation and the leaching behavior was observed not to change from that before irradiation.

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Abstract  

A new high-nitrogen complex [Cu(Hbta)2]·4H2O (H2bta = N,N-bis-(1(2)H-tetrazol-5-yl) amine) was synthesized and characterized by elemental analysis, single crystal X-ray diffraction and thermogravimetric analyses. X-ray structural analyses revealed that the crystal was monoclinic, space group P2(1)/c with lattice parameters a = 14.695(3) Å, b = 6.975(2) Å, c = 18.807(3) Å, β = 126.603(1)°, Z = 4, D c = 1.888 g cm−3, and F(000) = 892. The complex exhibits a 3D supermolecular structure which is built up from 1D zigzag chains. The enthalpy change of the reaction of formation for the complex was determined by an RD496–III microcalorimeter at 25 °C with the value of −47.905 ± 0.021 kJ mol−1. In addition, the thermodynamics of the reaction of formation of the complex was investigated and the fundamental parameters k, E, n,
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,
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, and
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were obtained. The effects of the complex on the thermal decomposition behaviors of the main component of solid propellant (HMX and RDX) indicated that the complex possessed good performance for HMX and RDX.
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Abstract  

[Cd(NTO)4Cd(H2O)6]4H2O was prepared by mixing the aqueous solution of 3-nitro-1,2,4-triazol-5-one and cadmium carbonate in excess. The single crystal structure was determined by a four-circle X-ray diffractometer. The crystal is monoclinic, space group C2/c with crystal parameters of a=2.1229(3) nm, b=0.6261(8) nm, c=2.1165(3) nm, β=90.602(7), V=2.977(6) nm3, Z=4, Dc=2.055 gcm−3, μ=15.45 cm−1, F(000)=1824, λ(MoKα)=0.071073 nm. The final R is 0.0282. Based on the results of thermal analysis, the thermal decomposition mechanism of [Cd(NTO)4Cd(H2O)6]4H2O was derived. From measurements of the enthalpy of solution of [Cd(NTO)4Cd(H2O)6]4H2O in water at 298.15 K, the standard enthalpy of formation, lattice energy, lattice enthalpy and standard enthalpy of dehydration have been determined as -(1747.84.8), -2394, -2414 and 313.6 kJ mol−1 respectively.

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Alanine- and taurine-salicylal Schiff base complexes of magnesium

Synthesis, characterization and thermal decomposition

Journal of Thermal Analysis and Calorimetry
Authors: S. Luan, Y. Zhu, and Y. Jia

Abstract  

The complexes of α-alanine-salicylal Schiff base of magnesium (α-ASSM), β-alanine-salicylal Schiff base of magnesium (β-ASSM) and taurine-salicylal Schiff base of magnesium (TSSM) were synthesized. The formulae of the complexes are Mg[OC6H4CHNCH(CH3)COO]·2H2O, Mg[OC6H4CHNCH2CH2COO]·2H2O and Mg[OC6H4CHNCH2CH2SO3]·2H2O. The crystal structure belongs to orthorhombic system with the lattice parameters: a=1.6954 nm, b=2.0873 nm and c=2.3037 nm for the β-ASSM, to orthorhombic system with the lattice parameters: a=1.5586 nm, b=1.8510 nm and c=2.6240 nm for the β-ASSM, to monoclinic system with the lattice parameters: a=1.3232 nm, b=1.4960 nm, c=2.1543 nm and β=98.04° for the TSSM, respectively. The results of the thermal decomposition processes and infrared spectra of the complexes show that the complexes may possess different coordination structures.

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Abstract  

N,N′-bis(salicylidene)-1,3-propanediamine (LH2), N,N′-bis(salicylidene)-2,2′-dimethyl-1,3-propanediamine (LDMH2), N,N′-bis(salicylidene)-2-hydroxy-1,3-propanediamine (LOH3), N,N′-bis(2-hydroxyacetophenylidene)-1,3-propanediamine (LACH2) and N,N′-bis(2-hydroxyacetophenone)-2,2′-dimethyl-1,3-propanediamine (LACDMH2) were synthesized and reduced to their phenol-amine form in alcoholic media using NaBH4 (LHH2, LDMHH2, LOHHH2, LACHH2 and LACDMHH2). Heterodinuclear complexes were synthesized using Ni(II), Zn(II) and Cd(II) salts, according to the template method in DMF media. The complex structures were analyzed using elemental analysis, IR spectroscopy, and thermogravimetry. Suitable crystals of only one complex were obtained and its structure determined using X-ray diffraction, NiLACH�CdBr2�DMF2, space group orthorhombic, Pbca, a=20.249, b=14.881, c=20.565 � and Z=8. The heterodinuclear complexes were seen to be of [Ni�ligand�MX2�DMF2] structure (ligand=LH2−, LDMH2−, LOHH2−, LACH2−, LACDMH2−, M=ZnII, CdII, X=Br, I). Thermogravimetric analysis showed irreversible bond breakage of the coordinatively bonded DMF molecules followed by decomposition at this temperature.

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Transition metal complexes with pyrazole based ligands

Part XXV. Deaquation of isostructural cobalt(II) and nickel(II) complexes with 3,5-dimethylpyrazole-1-carboxamidine

Journal of Thermal Analysis and Calorimetry
Authors: Katalin Mészáros Szécsényi, V. Leovac, R. Petković, Ž. Jaćimović, and G. Pokol

Abstract  

The deaquation of two isostructural compounds of general formula [M(HL)2(H2O)2](NO3)2 (M=Co, Ni, HL=3,5-dimethyl-1H-pyrazole-1-carboxamidine) is discussed in the view of their crystal and molecular structure. The compounds contain the same number and type of hydrogen bonds of the adjacent nitrate ions, only in the opposite orientation. On the basis of their deaquation pattern such a small difference may be detected, i.e., methods of thermal analysis are sensitive enough to show very small structural differences.

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Abstract  

The formation of TiO2 prepared by hydrolysis method was presented. Thermodynamics and kinetics of anatase crystallization reaction were investigated. Differential method of kinetic data evaluation in non-isothermal conditions according toKissinger, Ozawa and Kazeev-Yerofeev was applied. Starting, crystallized and thermally treated powders were determined using X-ray powder diffraction analysis. The characteristic parameters (the activation energy, constant rate and formal kinetic order of reaction) of TiO2 formation were calculated using DSC data.

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Thermal latent coordination compounds

II. The thermal degradation of imidazole and pyrazole adducts of metal(II) picolinate and quinaldinate

Journal of Thermal Analysis and Calorimetry
Authors: M. Döring, J. Wuckelt, W. Ludwig, and H. Görls

Abstract  

Complexes of the type M(Pa)2(HAz)2 and M(QA)2(HAz)2 (M=cobalt(II) and nickel(II); HPa=picolinic acid, HQa=quinaldic acid; HAz=azoles like imidazole (Him), pyrazole (HPz), benzimidazole (HBzIm) etc.) show a similar thermal behaviour. In the first step of decomposition the corresponding azolinium picolinates or quinaldinates (H2AzPa, H2AzQa) are split off with formation of polymeric mixed ligand complexes M(Pa)(Az) or M(Qa)(Az). X-ray analysis of Co(Qa)2(HBzIm)2 XIIIa illustrates a proton transfer and a subsequent thermal removal of benzimidazolinium quinaldinate (H2BzImQa): Hydrogen bridges from pyrrole nitrogen of the benzimidazole to the non-coordinated oxygen of the quinaldinate predetermine the thermal initiated proton transfer. The high volatility of the heterocyclic acids and the nitrogen coordination are responsible for the formation of the mixed ligand complex Co(Qa)(BzIm) XIVa. Exceptions are the complexes M(Pa)2(HPz)2 XIa-b and M(Qa)2(HIm)2 XVIIa-b. Pyrazole is eliminated from the complexes XIa-b with formation of the solvent-free inner complex M(Pa)2 XIIa-b. From compounds XVIIIa-b quinaldic acid or their decomposition products are split off and a high temperature modification of M(Im)2 XVIIIa-b is formed at elevated temperature. XVIIIa-b are decomposed to the cyanides M(CN)2 similarly to the thermal behaviour of Cu(Im). In the first step the thermal degradation of imidazole and pyrazole adducts of copper(II) picolinates and quinaldinates is characterized by the elimination of azoles. The reason for this thermal behaviour is the weaker coordination of the azole heterocycles in copper chelate compounds.

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Abstract  

The thermal and structural characteristics of two crystal forms of ambroxol, (trans-((amino-2-dibromo-3,5-benzyl)amino)-4-cyclohexanol), a drug with remarkable mucolytic and expectorant properties marketed in several drug products, were investigated. Form II (m.p. 92.4C) is obtained by spontaneous cooling from a hot water/ethanol solution while Form I (m.p. 99.5C) slowly separates from the mother liquor. The two forms can be identified by PXRD and DSC analyses. On the basis of both thermal and structural data the thermodynamic relationship of enantiotropy was deduced. No metastable (Form I)?stable (Form II) conversion was observed upon storage at ambient conditions. Form I crystallizes in the space group P21/n (alternative setting of P21/c) with Z=8. Form II crystallizes in the space group P21/c with Z=4 and a significantly different crystal packing arrangement from that in Form I. A third crystalline modification, Form III (space group P21/c with Z=16) was detected on cooling a single crystal of Form I down to -70C. On warming to ambient temperature Form III was found to revert to Form I. This reversible single crystal to single crystal transition was structurally characterised and found to involve subtle changes in the types and extent of molecular disorder as well as the hydrogen bonding arrangement.

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