Water-vapor pressure and thermodynamics of the dehydration of manganese,nickel, cadmium,and lead perchlorate hydrates

The water-vapor pressure has been measured by a static method, the temperature limits for existence have been determined, and the parameters of the equation lgp [Torr]=b —a/T have been calculated for the following crystal hydrates: Mn(ClO₄)₂ · 2H₂O (90–130°C, a=3527.0,b=8.487), Ni(ClO₄)₂ · 4H₂O (60–100°C,a=3606.7,b=9.704), Ni(C1O₄)₂ · 2H₂O (110–160°C,a = 4261.7,b = 10.103), Cd(ClO₄)₂ · 6H₂O (25–58.2°C,a = 3143.7,b = 9.356), Cd(ClO₄)₂ · 2H₂O (90–144.8°C,a=3823.3,b = 9.472), Pb(ClO₄)₂ · 3H₂O (10–47°C,a = 2932.9,b = 9.391 and 47–81.5°C,a = 2448.1,b=7.877), Pb(ClO₄)₂ · H₂O (60–102.4°C,a=3610.2,b = 9.857). A hitherto unknown metastable hydrate Cd(ClO₄)₂ · 4H₂O with a phase transition at 30.9°C (20–30.9°C,a = 3669.5,b = 11.343 and 30.9–63.7°C,a=3058.6,b = 9.339) has been detected.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 466–470, March, 1993.     

The effect of the water vapor pressure on the kinetics of thermal dehydration of manganese(II) formate dihydrate

The effect of the water vapor pressure on the thermal dehydration of manganese(II) formate dihydrate was studied by means of isothermal gravimetry under various water vapor pressure, ranging from 4.6 to 24.4 torr. The kinetics of dehydration was described by a two-dimensional phase-boundary model,R ₂. The rate of dehydration decreased with increasing atmospheric water vapor pressure, but the Smith-Topley phenomenon was not observed for the present dehydration. The activation energy and the frequency factor for the dehydration were 110–170 kJ·mol⁻¹ and 10¹⁰–10¹⁶ cm·s⁻¹, respectively. These values increased with increasing water vapor pressure, and were much larger than those reported for the dehydration in vacuum.     

Dependence of Thermal Decomposition Rate Constant on Temperature of Reaction

On the basis of results of kinetic investigates of many compounds general temperature dependence of Gibbs free energy of activated complexes created in thermal decomposition processes and the reaction rate constant were calculated. This revised version was published online in July 2006 with corrections to the Cover Date.     

Kinetics of the dehydration of 2-propanol on modified activated charcoal containing acid sites

A study was carried out on the kinetics of the dehydration of 2-propanol on activated bone charcoal (ABC) with supported acid sites. The rate-limiting step is the loss of water from the alcohol molecule adsorbed on the acid site. The sites containing the minimum amount of water are the most active. The reaction on these sites presumably proceeds through a concerted mechanism, which is possible at sufficiently high temperatures (above 120 °C). Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 5, pp. 321–327, September–October, 2008.     

丙硫异烟胺的热稳定性及其热分解动力学

通过热重法研究了抗结核药物丙硫异烟胺的热稳定性, 计算了该药物的动力学参数并建立了热分解动力学方程. 用Kissinger和Ozawa-Flynn-Wall两种方法计算该药物热分解过程的活化能Ea=54.65 kJ·mol-1. 用Malek法推断该药物的动力学机理函数及指前因子A, 其结果分别为f(α)=α0.391(1-α)0.145, lnA=13.12. 此外, 用差热法测定该物质的熔点、摩尔熔化焓和摩尔熔化熵, 分别是414.09 K、23.21 kJ·mol-1和56.06 J·mol-1·K-1.     

Physical characterization of some complexes of organic nitrogen donor compounds

The stability constants of the complexes of cyanopyridine and aminoantipyrine with some divalent transition metal chlorides were determined at different temperatures. The thermodynamic parameters were calculated; the obtained data reveal that the complexation is an endothermic process. Also it was found that the type of bonding between the ligands and the corresponding metal ion is mainly ionic in nature. The stoichiometry of the formed complexes was found to be M:L and M:2L. The structure of some prepared complexes was confirmed by IR, ¹H NMR spectra as well as elemental analysis. Thermal stability was studied using TGA technique.     

Synthesis,characterization, and properties of copper and manganese complexes with 5-(benzimidazol-1-ylmethyl)isophthalate

Four new complexes, [Cu(L)] (1), [Cu₂(L)(dpe)_0.5]?·?2.5H₂O (2), [Mn(L)] (3), and [Mn(L)(pybim)] (4) [H₂L?=?5-(benzimidazol-1-ylmethyl)isophthalic acid, dpe?=?1,2-di(pyridin-4-yl)ethylene, pybim?=?2-(pyridin-2-yl)-1H-benzimidazole], have been synthesized under hydrothermal conditions and characterized by single-crystal and powder X-ray diffractions, FT-IR, and elemental analysis. The crystal structural analyses reveal that 1 and 4 are uninodal 3-connected 2-fold interpenetrated 2-D networks with (6³) topology, 2 shows an infinite 1-D double-stranded chain structure, and 3 exhibits a uninodal 4-connected 2-D network with (4⁴?·?6²) topology. The factors influencing the structures of the coordination polymers are discussed. In addition, the thermal stabilities of 1–4, second-order non-linear optical effect of 1, and preliminary magnetic property of 3 have also been investigated.     

Equilibria of formation and dehydration of the carbinolamine intermediate in the reaction of benzaldehyde with hydrazine

Measurement of polarographic limiting currents at equilibria made it possible at pH 3-7 to simultaneously determine concentrations of benzaldehyde, of its hydrazone and of the carbinolamine derivative. The dependence of concentration of carbinolamine at equilibrium on pH indicated presence of its di-, mono-, and unprotonated forms. Acid dissociation constants of the formation (pK_a¹≈3.2) of the diprotonated form and of the dissociation of the monoprotonated form of carbinolamine (pK_a²≈4.7) were estimated. The equilibrium constants of formation (K₁) and dehydration (K₂) of the carbinolamine intermediate were determined.     

Thermal and Spectral Characterization of 5-Cholro-2-methoxybenzoates of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)

The thermal stabilities of 5-chloro-2-methoxybenzoates of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) were studied in air and nitrogen atmospheres. The complexes were obtained as mono-, di-, tetra-and pentahydrates with a metal to ligand ratio of 1:2 and with colours typical for M²⁺ ions (Mn-slightly pink, Co-pink, Ni-green, Cu-blue and Zn-white) and as polycrystalline compounds. When heated they dehydrate to form anhydrous salts which nextare decomposed to the oxides of the respective metals in air while in nitrogen to the mixtures of metal oxides and oxychlorides and carbon. The most thermally stable in air, nitrogen and argon atmospheres is 5-chloro-2-methoxybenzoate of Cu(II) while the least thermally stable is that of Co(II). This revised version was published online in July 2006 with corrections to the Cover Date.     

镧系元素Dawson结构钨钒磷四元杂多配合物的合成、表征以及对H2O2分解的催化活性

合成了通式为K₁₅H₃[Ce(P₂W₁₆VO₆₁)₂]·61H₂O、K₁₅H₄[Ln(P₂W₁₆VO₆₁)₂]·xH₂O(Ln=La³⁺,Pr³⁺,Nd³⁺,Sm³⁺,Eu³⁺,Gd³⁺,Dy³⁺,Yb³⁺)的9种镧系元素Dawson结构的钨钒磷四元杂多配合物,并用IR、UV、NMR、ESR、XRD、TG-DTA等对其结构和性质进行了研究。该类配合物具有与K₁₆[Ce(P₂W₁₇VO₆₁)₂]·50H₂O类似的结构,对H₂O₂分解有较高的催化活性。     

Preparation and dehydration behaviour of thomsonite with ideal chemical composition

Thomsonite with ideal chemical composition and with an ordered framework structure was synthesised hydrothermally from zeolite Na?A, which was ground to X-ray amorphous, with 0.05 mol dm^?3 CaCl₂ solution at 200°C. The dehydration behaviour of the prepared thomsonite was examined by TG-DTA. It was revealed that thomsonite lost most of zeolitic water below 450°C in three steps at about 180°, 340° and 390°C. The peak profiles of, the two higher-temperature endotherms were sharp and similar, and the weight loss at each step was approximately equal.     

The preparation and reactivity of metal-containing monomers. 54. Thermolysis of the acrylamide monomer [Co(CH2=CHCONH2)4(H2O)2](NO3)2

The kinetics and pathways of thermolysis of the Co(II) complex with acrylamide, [Co(CH₂=CHCONH₂)₄(H₂O)₂](NO₃)₂ (1) were studied. The rate of gas evolution is satisfactorily approximated by a first-order equation of autocatalysis. The composition of gaseous and solid products of thermolysis of 1 was studied by IR spectroscopy, mass spectrometry, and electronic microscopy. Thermal transformations of acrylamide complex 1 include three macro stages: dehydration, polymerization of the dehydrated monomer, and thermooxidative destruction of the resulting polymer.     

Synthesis,X-ray crystallography,spectroscopy, electrochemistry,thermal and kinetic study of uranyl Schiff base complexes

Uranyl(VI) complexes [UO₂(L)(solvent)], where L denotes an asymmetric N₂O₂ Schiff base (salpyr, 3-MeOsalpyr, 4-MeOsalpyr, 5-MeOsalpyr, 5-Clsalpyr or 5-Brsalpyr; salpyr is N,N′-bis(salicyliden)-2,3-diaminopyridine), were synthesized and characterized in solution (UV–vis, ¹H NMR, cyclic voltammetry) and in the solid-state (X-ray crystallography, IR, TGA, C H N.). X-ray crystallography of UO₂(3-MeOsalpyr) revealed coordination of the uranyl by the tetradentate Schiff base and one disordered solvent, resulting in seven-coordinate uranium. Another disordered solvent was not coordinated. Cyclic voltammetry of [U^VIO₂(L)(solvent)] in acetonitrile was used to investigate the effect of the substituents of the Schiff base ligands on oxidation and reduction potential. The quasi-reversible redox reaction without any successive reactions was accelerated by groups with lesser electron withdrawing. We also investigated the kinetics and mechanism of the exchange reaction of the coordinated solvent with tributylphosphine using spectrophotometric method. The second-order rate constants at four temperatures and activation parameters showed an associative mechanism for all corresponding complexes with the following trend: UO₂(5-Clsalpyr)?>?UO₂(5-Brsalpyr)?>?UO₂(3-MeOsalpyr)?>?UO₂(4-MeOsalpyr)?>?UO₂(salpyr)?>?UO₂(5-MeOsalpyr). It was concluded that the steric and electronic properties of the complexes were important for the reaction rate.     

Kinetics of the solvolysis of thetrans-dichlorobis (Diaminoethane)-cobalt(III) ion in aqueous ethylene carbonate and aqueous propylene carbonate

The kinetics of the solvolysis of trans-[Coen₂Cl₂]⁺ have been followed in mixtures of water with either ethylene carbonate or propylene carbonate over a range of temperatures. Both the enthalpy and entropy of activation for the first order loss of a chloride ion to give [Coen₂Cl]²⁺ in water + ethylene carbonate show a maximum at low mole fractions of ethylene carbonate. As similar extrema in H and S for the same process for this complex and others in water +2-propanol and in water + t-butanol correlate well with extrema in the physical properties of the mixtures which are influenced by changes in solvent structure, it is suggested that these new extrema can be attributed to solvent structure effects. The application of a free energy cycle to the loss of the chloride ion in water and in the mixtures suggests that, although changes in solvent structure influence the cation in the transition state more than the cation in the initial state in water + ethylene carbonate, in water + propylene carbonate the influence of changes in solvent structure approximately balances. This is compared with the application of the free energy cycle to the same process in mixtures of water with a range of cosolvents using kinetic data available in the literature.     

Thermal properties of complexes of lanthanides(III) and some of d-block elements with 5-chloro-2-methoxybenzoic acid

The thermal properties of 5-chloro-2-methoxybenzoates of lanthanides(III) and Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) were studied in air and nitrogen atmospheres. The complexes were obtained as mono-, di-, tetra- and pentahydrates with a metal to ligand ratio of 1:3 (in the case of lanthanides(III)) and 1:2 (in the case of d-block elements). They have colours typical for Ln³⁺ and M²⁺ ions. All complexes are polycrystalline compounds. When heated they dehydrate to form anhydrous salts which next in air are decomposed to the oxides of the respective metals while in nitrogen to the mixtures of metal oxides, oxychlorides and carbon. This revised version was published online in July 2006 with corrections to the Cover Date.     

Theoretical insights into the absorption and emission properties of blue luminescent copper(I) complexes based on the pyrazolyl‐pyridine ligands

The ground geometrical and electronic structures, charge transfer (CT) behaviors, absorption, and emission properties of the three copper(I) complexes [Cu(pypz)(POP)]⁺ (1) , [Cu(pympz)(POP)]⁺ (2) , and [Cu(pytfmpz)(POP)]⁺ (3) (pypz=1‐(2‐pyridyl)pyrazole, pympz=3‐methyl‐1‐(2‐pyridyl)pyrazole, and pytfmpz=3‐trifluoromethyl‐1‐(2‐pyridyl)pyrazole), have been investigated using density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT). The vertical absorption energies of the all copper(I) complexes are well reproduced by TD‐DFT calculations based on the CT amount calculations. The triplet emission properties of the all copper(I) complexes were correctly evaluated at BMK/LANL2DZ/6‐31G* level of theory. In addition, the thermally activated delayed fluorescence properties of 1–3 were discussed in detail based on the spatial separation of the HOMO and LUMO and vertical excited energies. These theoretical insights should be expected to provide some guides for the design and synthesis of efficient luminescent copper(I) complexes. © 2014 Wiley Periodicals, Inc.     

Thermal Studies on Some Ionic Chelates of Hafnium(IV)

Ionic chelate complexes of kojic acid(I) and hafnium(IV) of the type [(η⁵-C₅H₅)₂HfL]⁺[MCl₃]^– (II)[HL=kojic acid; M=Zn(II), Cd(II), Hg(II), Cu(II)] have been synthesised and characterised by spectral studies (IR, UV, ¹H NMR and ¹³CNMR). Thermogravimetric (TG) and differential thermal analytical (DTA) studies have been carried out for these complexes and from the TG curves, the order and apparent activation energy for the thermal decomposition reactions have been elucidated. The various thermal studies have been correlated with some structural aspects of the complexes concerned. From DTA curves, the heat of reaction has been calculated. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal behaviour of complexes of antipyrine derivatives II

Parent and mixed ligand complexes of cobalt(II) and copper(II) ions with N,N-bis-(4-antipyrylmethyl)piperazine or N,N-tetra(4-antipyryl-methyl)-1,2-diaminoethane or/and imidazole as ligand and ClO ₄ ^– or SCN^– as counterion were synthesised and their thermal behaviour was investigated.This work was performed in the framework of cooperation between the Hungarian Academy of Sciences and Romanian Academy and was supported financially, in part, by the Hungarian Scientific Research Foundation (OTKA T 029554).     

Thermal,spectral and magnetic behaviour of 4-chloro-2-methoxybenzoates of light lanthanides(III)

4-Chloro-2-methoxybenzoates of light lanthanides(III) were obtained as mono-, di-or trihydrates with metal to ligand ratio of 1:3 and general formula Ln(C₈H₆ClO₃)₃·nH₂O, where n=1 for Ln=Ce, Pr, n=2 for Ln=Nd, Sm, Eu, Gd and n=3 for Ln=La. The complexes were characterized by elemental analysis, IR spectra, thermogravimetric studies, X-ray diffraction and magnetic measurements. The carboxylate group appears to be a symmetrical bidentate, chelating ligand. All complexes seem polycrystalline compounds. Their thermal stabilities were determined in air. When heated they dehydrate to form anhydrous salts which next are decomposed to the oxides of the respective metals. The solubilities of light lanthanide(III) 4-chloro-2-methoxybenzoates in water at 293 K are of the order of 10⁻⁵ mol dm⁻³. The magnetic moments were determined over the range of 77–300 K. They obey the Curie-Weiss law. The values of μ_eff calculated for all compounds are close to those obtained for Ln³⁺ by Hund and Van Vleck. The results indicate that there is no influence of the ligand field of 4f electrons on lanthanide ions and the metal ligand bonding is mainly electrostatic in nature.