Synthesis, structural and thermal characterization of metaphosphatenickel(II) salt

A new inorganically template metaphosphate of Ni(II) complex has been synthesized and characterized by different measurements such as DSC, FT-IR, C?CH?CN?CS, X-RD and ICP-AES. Differential scanning calorimeter (DSC) elucidated negative specific heat of the system and has used to evaluate some thermodynamical constants like specific heat, enthalpy and entropy of that system. The specific heat capacity of the system is measured in atmospheric O₂ at heating rate of 278 and 283?K?min^?1. The specific heat is found both positive and negative at 278?K?min^?1.     

Synthesis,structural and thermal characterization of metaphosphatecobalt(II) salt

A new inorganically template metaphosphate of Co(II) complex has been synthesized and characterized by different measurements such as DSC, FT-IR, C–H–N–O–S, ESR, TG-DTA and X-RD. Differential Scanning Calorimeter (DSC) elucidated negative specific heat of the system and has used to evaluate some thermo dynamical constants like activation energy (E _a), frequency factor (A), enthalpy and entropy of that system. The specific heat capacity of the system is measured both in atmospheric O₂ and N₂ atmosphere at different heating rates of 278, 283, 293 and 298 K min⁻¹ in room atmosphere and 288 K min⁻¹ in N₂ atmosphere.     

Synthesis and thermal behaviors of 1,3-bis(4-aminophenoxy)benzene (TPER) and polyimide based on TPER and pyromellitic dianhydride

1,3-Bis(4-aminophenoxy)benzene (TPER) and poly(amic acid) based on TPER and pyromellitic dianhydride (PMDA) were synthesized. After imidization of the poly(amic acid), polyimide based on TPER and PMDA was obtained. The melting process and the specific heat capacity (C _p) of TPER were examined by DSC and microcalorimetry, respectively. The melting enthalpy, the melting entropy, and the C _p for TPER were obtained. The enthalpy change, the entropy change, and the Gibbs free energy change for TPER were obtained within 283 and 353 K. The thermal decomposition reaction mechanism of the polyimide is classified from the TG–DTG experimental data, and the thermokinetic parameters of the thermal decomposition reaction are E _a = 296.87 kJ mol^?1and log (A/s^?1) = 14.41.     

Exchange interaction and orbital degeneracy in the Cu(II)-Co(II) heterobinuclear complex

The temperature dependence of the magnetic susceptibility of the title compound was studied in the range 3.6–300 K. This heterobinuclear complex may be considered as the simplest polynuclear system in which the problem of the orbital degeneracy occurs. The experimental data were interpreted with a hamiltonian taking into account the distorsion and the spin-orbit coupling around the Co(II) ion on one hand, and the Cu(II)-Co(II) interaction on the other. From this hamiltonian, a quite satisfying simulation of the experimental magnetic curve was obtained. The effective exchange interaction parameter J of the ?J?_Cu?_Co term of the hamiltonian was found equal to =62 ± 2 cm^?1. This value was compared to those obtained with the [CuCu], [CuNi] and [CuMn] complexes prepared with the same bichelating ligand. This comparison was carried out in a framework of an orbital model, previously established in the case of interacting ions without orbital momentum and here extended to the case where one of the interacting ions has an orbital degeneracy.     

2-Bis(carboxymethyl)-amino-5-hydroxy-terephthalsäure als ambifunktioneller Ligand in Eisen(III)-Komplexen

2-Bis(carboxymethyl)-amino-5-hydroxy-terephthalic Acid as an Ambifunctional Ligand in Iron(III) Complexes From steric reasons the anthranilic acid -N,N-diacetic acid group and the salicylic acid group of 2-bis(carboxymethyl)-amino-5-hydroxy-terephthalic acid (H₅C) cannot coordinate to the same central atom. With iron(III) H₅C forms the mononuclear complex (HC)Fe(OH)^2?, the central atom is fixed to the anthranilic acid N,N-diacetic acid group. In a weak acid medium (HC)Fe(OH)^2? is converted into the binuclear species (HC)Fe(C)Fe(OH)^4? which is of a deep red colour. In this complex the anion C^5?has the function of a bridging ligand coordinating both by the anthranilic acid-N,N-diacetic acid group and by the salicylic acid group. The complex formation in the ternary system iron(III)/nitrilo triacetic acid/5-sulfo salicylic acid may be used as model for the dimerisation of the anion (HC)Fe(OH)^2?.     

Equilibrium study of the systems of aluminium(III), gallium(III) and indium(III) with mercaptoacetate, 3-mercaptopropionate and 2-mercaptobenzoate

Equilibrium studies were carried out by pH-potentiometry on the systems of aluminium(III), gallium(III) and indium(III) with mercaptoacetate (MerAc^2?), 3-mercaptopropionate (MerPr^2?) and 2-mercaptobenzoate (MerBe^2?). It was found that the complex-forming properties of the Al³⁺ ion towards these mercaptocarboxylic acid ligands differ from those of Ga³⁺ and Al³⁺. Under the conditions of the study, Al³⁺ forms only hydroxo complexes, while Ga³⁺ and In³⁺ form relatively stable complexes involving the simultaneous coordination of the carboxylate and the deprotonated mercapto group. In all cases the equilibrium systems can be described without the assumption of polynuclear complexes. The complexes Ga(MerAc)₂ and Ga(MerBe)₂ show marked stability; this was interpreted in terms of back-coordination and of interaction between the d¹⁰ electrons of the Ga³⁺ ion and the empty d orbitals of the S donor atom. Complexes of composition ML_i are not formed in the Ga³⁺-MerPr^2? system; this points to the importan roles of the number of atoms in the chelate ring and the higher stability of the Ga(III)-hydroxo complexes.     

Determination of specific heat capacity and standard molar combustion enthalpy of taurine by DSC

Using XRY-1C calorimeter, the standard molar enthalpy of taurine was determined to be ?2546.2?kJ?mol^?1 . The reliability of the instrument used was tested by using naphthalene as reference material; and through comparing the molar combustion enthalpy of naphthalene measured with its standard value found in literature, the absolute error and relative error were found to be 4.53?kJ?mol^?1 and 0.09%, respectively. The melting point and melting enthalpy of taurine were determined by Differential Scanning Calorimetry (DSC), which was found to be 588.45?K and ?22.197?kJ?mol^?1, respectively. Moreover, using the DSC method, the specific heat capacities C _p of taurine was measured and the relationship between C _p and temperature was established. The thermodynamic basic data obtained are available for the exploiting new synthesis method, engineering design and industry production of taurine.     

Thermal properties of pure and doped (polyvinyl-alcohol) PVA

Films ≈350 μm of poly(vinyl-alcohol) composites, containing copper (Cu), aluminium (Al) and iron (Fe), metallic powder very fine, were prepared by a casting method. Thermal conductivity, phonon velocity, mean free path and specific heat were studied. The pure sample of PVA has a lower values of thermal conductivity than that which are doped with metals. For all samples the thermal conductivityK increases up to a certain temperatureT _gg (120–160°C) and then decreases with temperature. The specific heat increase with temperature up to ≈120°C and above 120°C is nearly independent on temperature. The pure sample of PVA has small values of mean free path (L)≈0.2 Å at room temperature, but for PVA⁺ metalsL≈2.0 Å. The phonon velocity of pure PVA is larger than that of PVA containing metals.     

Chelate von β-Dicarbonylverbindungen und ihren Derivaten. XVII. Zur Kristallstruktur von Bis-(thioisobutyrylacetonato)-nickel(II)

The x-ray structure analysis of the title Ni^II compound being of the planar coordination type Ni[S₂O₂] gives Ni? S distances of 2.15 Å and Ni? O distances of 1.87 Å. The sulfur atoms are arranged in cis-position. In the chelate ring the C? C distance is shortened in sulfur neighbourhood. This indicates a fixation of the C?C double bonds in the complex.     

Thermodynamic properties of complex compounds of iron(II) nitrate with tris(3,5-dimethylpyrazol-1-yl)methane

The temperature dependence of the heat capacity of a complex compound of iron(II) nitrate with tris(3,5-dimethylpyrazol-1-yl)methane is studied by adiabatic calorimetry in the range of 100–300 K. A specific heat anomaly is found and localized in the temperature range corresponding to the sharp spin transition ¹ A ₁ ? ⁵ T ₂ with hysteresis on the temperature dependence of the magnetic susceptibility. The effects of cooperative interaction are revealed on the basis of thermodynamic and magnetochemical data, using two widely used models of spin transition.     

Reaction of dirhodium(II) tetraacetate with S-methyl-L-cysteine

Abstract

The reaction of antitumor active dirhodium(II) tetraacetate, [Rh₂(AcO)₄], with S-methyl-L-cysteine (HSMC) was studied at the pH of mixing (=4.8) in aqueous media at various temperatures under aerobic conditions. The results from UV–vis spectroscopy and electrospray ionization mass spectrometry (ESI–MS) showed that HSMC initially coordinates via its sulfur atom to the axial positions of the paddlewheel framework of the dirhodium(II) complex, and was confirmed by the crystal structure of [Rh₂(AcO)₄(HSMC)₂]. After some time (48?h at 25?°C), or at elevated temperature (40?°C), Rh-SMC chelate formation causes breakdown of the paddlewheel structure, generating the mononuclear Rh(III) complexes [Rh(SMC)₂]⁺, [Rh(AcO)(SMC)₂] and [Rh(SMC)₃], as indicated by ESI–MS. These aerobic reaction products of [Rh₂(AcO)₄] with HSMC have been compared with those of the two proteinogenic sulfur-containing amino acids methionine and cysteine. Comparison shows that the (S,N)-chelate ring size influences the stability of the [Rh₂(AcO)₄] paddlewheel cage structure and its Rh^II–Rh^II bond, when an amino acid with a thioether group coordinates to dirhodium(II) tetraacetate.     

Electron impact ionization mass spectra of lithocholyl amides: Evidence for a C(20) to C(23) rearrangement involving the loss of a C4H9 fragment

Amides of lithocholic acid (3α-hydroxy-5β-cholan-24-oic acid) with 6-aminocaproic acid and 4-aminobutyric acid were prepared and examined by electron impact ionization mass spectrometry. Both these compounds gave an unusual [M ? 57]⁺ fragment. Since the product-ion analysis of [M ? 57]⁺ revealed the presence of fragments corresponding to the intact steroid nucleus in addition to that of the original amino acid (6-aminocaproic acid or 4-aminobutyric acid), we concluded that the integrity of the steroid amide had been retained in this fragment. The absence of this fragment from the product-ion spectrum of [M ? CH₃]⁺ rules out the sequential loss from the molecular ion of 15 + 42 u as the origin of this signal. Mass spectrometry of the 24-¹³C-labelled lithocholylcaproylamide showed the retention of the label in the [M ? 57]⁺ fragment. In contrast, the corresponding compound labelled with deuterium at C(23) showed a significant loss of the label during the formation of this product ion at [M ? 58]⁺. In addition, through a combination of derivatization and tandem mass spectrometry, it was demonstrated that this loss of 57 u represented a rearrangement with the expulsion of a C₄H₉ radical from the side-chain spanning C(20) to C(23) resulting in a truncated steroid-amide fragment. This fragmentation pattern has not been observed in bile acid conjugates with N-α-amino acids.     

Calorimetric studies on the thermal decomposition of tri n-butyl phosphate-nitric acid systems

Thermal decomposition of neat TBP, acid-solvates (TBP·1.1HNO₃, TBP·2.4HNO₃) (prepared by equilibrating neat TBP with 8 and 15.6?M nitric acid) with and without the presence of additives such as uranyl nitrate, sodium nitrate and sodium nitrite, mixtures of neat TBP and nitric acid of different acidities, 1.1?M TBP solutions in diluents such as n-dodecane (n-DD), n-octane and isooctane has been studied using an adiabatic calorimeter. Enthalpy change and the activation energy for the decomposition reaction derived from the calorimetric data wherever possible are reported in this article. Neat TBP was found to be stable up to 255?°C, whereas the acid-solvates TBP·1.1HNO₃ and TBP·2.4HNO₃ decomposed at 120 and 111?°C, respectively, with a decomposition enthalpy of ?495.8?±?10.9 and ?1115.5?±?8.2?kJ?mol^?1 of TBP. Activation energy and pre exponential factor derived from the calorimetric data for the decomposition of these acid-solvates were found be 108.8?±?3.7, 103.5?±?1.4?kJ?mol^?1 of TBP and 6.1?×?10¹⁰ and 5.6?×?10⁹?S^?1, respectively. The thermochemical parameters such as, the onset temperature, enthalpy of decomposition, activation energy and the pre-exponential factor were found to strongly depend on acid-solvate stoichiometry. Heat capacity (C _p ), of neat TBP and the acid-solvates (TBP·1.1HNO₃ and TBP·2.4HNO₃) were measured at constant pressure using heat flux type differential scanning calorimeter (DSC) in the temperature range 32?C67?°C. The values obtained at 32?°C for neat TBP, acid-solvates TBP·1.1HNO₃ and TBP·2.4HNO₃ are 1.8, 1.76 and 1.63?J?g^?1?K^?1, respectively. C _p of neat TBP, 1.82?J?g^?1?K^?1, was also measured at 27?°C using ??hot disk?? method and was found to agree well with the values obtained by DSC method.     

Equilibria in aqueous solution of cobalt(II), nickel(II) and copper(II) cations with furan-2-carboxylate. A calorimetric study

Summary The heat of reaction of the anion of furan-2-carboxylic acid with cobalt(II), nickel(II) and copper(II) cations has been determined by direct calorimetry. By means of the equilibrium constants, Gibbs function and entropy were also obtained. The measurements were carried out in aqueous medium at 25 °C and an ionic strength I=1 mol dm^–3 (NaNO₃). The data obtained seem to indicate a bidentate character of this ligand, with the participation of both carboxylate and heterocyclic oxygen in complex formation. The behaviour of furan oxygen towards 3d metals is compared with that of thiophen sulfur and pyrrole nitrogen.     

Kinetics of the thermal dehydration of trans-fluoroaquobis(ethylenediamine)chromium(III) tetracyanometallate(II) [metal(II) = Ni(II), Pd(II) and Pt(II)]

The solid phase thermal deaquation—anation of trans-[CrF(H₂O)(en)₂][M(CN)₄] (M = Ni, Pd, Pt; en = ethylenediamine) has been investigated by means of non-isothermal DSC and isothermal and non-isothermal TG measurements. The physical model for these reactions (nucleation, growth, diffusion or intermediates) has been found by comparison of the isothermal and non-isothermal TG data for all the principal g(α) expressions (0.2?α?0.8) and by the shape of the isothermal curves. The values found for activation energy are low (～ 130 kJ mol^?1 for the Ni compound, ～ 140 kJ mol^?1 for the Pd compound, and ～ 100 kJ mol^?1 for the Pt compound). These data permit the assignment of the deaquation—anation mechanism of the S_N1 type involving a square-base pyramid activated complex and elimination of water as Frenkel defects.     

Crystallization behavior of Mg–Cu–Y amorphous alloy

Amorphous Mg₆₁Cu₂₄Y₁₅ ribbons were manufactured by melt-spinning at wheel speeds in the range 5?C20?ms^?1. The crystallization behavior of amorphous ribbons was investigated by a combination of differential scanning calorimetry (DSC) and X-ray diffractometry. DSC measurements showed that the amorphous ribbons exhibit distinct glass transition temperature and wide supercooled liquid region before crystallization. During continuous heating three exothermic peaks and two endothermic peaks were observed. The characteristic thermodynamic parameters such as T _g, T _x , ??T _x , and T _rg are around 432?C439, 478?C485, 46?C54?K, and 0.55?C0.56, respectively. Isothermal annealing DSC traces for this amorphous alloy, the first crystallization peak showed a clear incubation period and Avrami exponent was found to be 2.30?C2.74, which indicate that the transformation reaction involved nucleation and three-dimensional diffusion controlled growth. Mechanical properties of the as-quenched and subsequently annealed ribbons were examined by Vickers microhardness (HV) measurements. Results showed that microhardness of the as-quenched ribbons were about 309?HV. However, the results also showed that microhardness of the rapidly solidified ribbons increases with the increasing temperature.     

Binuclear paddle-wheel platinum(II) and platinum(III) complexes containing 4-methyl-4H-1,2,4-triazole-3-thiol ligand: Synthesis,X-ray studies,and spectroscopic characterization

The complex [Pt₂(μ-mtrzt)₄(mtrzt)₂] (1) was synthesized from the reaction of a mixture of 4-methyl-4H-1,2,4-triazole-3-thiol (Hmtrzt) and ethylenediamine (en) with K₂PtCl₄ in CH₃OH/H₂O (2:1) as solvent. The complex [Pt₂(μ-mtrzt)₄] (2) was synthesized by the same procedure as described for preparation of complex 1 but in the absence of ethylenediamine. Both complexes were characterized by elemental analysis, IR,¹H NMR,¹³C{¹H}NMR, UV-Vis, as well as luminescence spectroscopy and their structures were analyzed by single-crystal X-ray diffraction method. The X-ray structure determinations show that complexes of 1 and 2 have binuclear structures in a paddle-wheel fashion with Pt-Pt distances of 2.6628(7) and 2.7977(16)Å, respectively. In complex 1, each platinum(III) atom has a distorted octahedral coordination geometry with the sulfur atom and the second platinum subunit in axial positions and two nitrogen and two sulfur atoms in equatorial positions. Also, in complex 2, each platinum(II) atom has a distorted square-pyramidal coordination geometry with the second platinum subunit in axial position and two nitrogen and two sulfur atoms in equatorial positions. In addition, intermolecular C?H···N and C?H···S hydrogen bonds in 1 and 2 as well as intermolecular anagostic C?H···Pt and C?H···π interactions in 2 are effective in the stabilization of the crystal packing of these complexes.     

Determination and comparison of stability constants of tungsten(VI) and molybdenum(VI) with nitrilotriacetic acid and glutamic acid at different ionic strengths

The formation constants of species formed in the systems H⁺?+?W(VI)?+?nitrilotriacetic acid (NTA) and H⁺?+?NTA have been determined in aqueous solution for pH?=?4–9 at 25°C and different ionic strengths ranging from 0.1 to 1.0?mol?dm^?3 NaClO₄, using potentiometric and spectrophotometric techniques. It was shown that tungsten(VI) forms a mononuclear 1?:?1 complex with NTA of the type WO₃L^3? at pH?=?7.5. The composition of the complex was determined by the continuous variations method. The complexation of molybdenum(VI) with glutamic acid was investigated in aqueous solution ranging in pH from 4 to 9, using polarimetric, potentiometric and spectrophotometric techniques. The composition of the complex was determined by the continuous variations method. It was shown that molybdenum(VI) forms a mononuclear 1?:?1 complex with glutamic acid of the type MoO₃L^2? at pH?=?6.0. The dissociation constants of glutamic acid and the stability constants of the complex were determined at 25°C and at ionic strengths ranging from 0.1 to 1.0?mol?dm^?3 sodium perchlorate. In both complex formation reactions the dependence of the dissociation and stability constants on ionic strength is described by a Debye-Huckel type equation. Finally, a comparison has been made between the patterns of ionic strength dependence for the two complexes and the results have been compared with data previously reported.     

Molecular structure and thermal behavior of N-Benzoyl-3,3-dinitroazetidine

N-Benzoyl-3,3-dinitroazetidine (BDNAZ) has been synthesized and characterized by elemental analysis, FT-IR spectroscopy, ¹H NMR and X-ray single crystal diffraction technique. BDNAZ crystallizes in the monoclinic space group P2₁/c. Its thermal behavior was studied under a non-isothermal condition by DSC and TG/DTG methods, the value of E _a and A of the exothermic decomposition reaction of BDNAZ are 143.19 kJ mol^?1 and 10^14.34 s^?1, respectively. The specific heat capacity of BDNAZ was determined with a continuous C _p mode of micro-calorimeter and theoretical calculation. The adiabatic time-to-explosion was evaluated as 109.9?C124.4 s.