Thermal decomposition of some metal chelates of substituted hydrazopyrazolones

The thermal dissociation of 1-phenyl-3-methyl-4-(X-phenylhydrazo)-5-pyrazolone metal chelates [M(XPhHyPy)](X=m-OH (I),m-OCH₃(II),m-COOH (III),p-CH₃ (IV),p-OCH₃ (V) orp-COCH₃ (VI) was studied by TG, DTG and differential thermal analysis (DTA). A rough sequence of thermal stability, obtained from the peak maximum temperatures, for the various metal chelates was Hg(II)2(II). The bonding of the ligands to metal ions was investigated by elemental analysis and infrared spectroscopy. The number and relative energies of nitrate combiantion frequencies are discussed in terms of the complexation of para-substituted hydrazopyrazolone with Th(IV) and UO₂(II) metal ions.     

Thermal decomposition reactions and kinetic parameters of nitritobismuthates(III)

Thermal studies have been carried out on nitritobismuthates(III) of the silver group having the general formula M₂Ag[Bi(NO₂)₆] where M = Cs, Rb, K, and the sodium group having the formula M₂Na[Bi(NO₂)₆] where M = Cs, Rb.Typical thermal curves, temperatures of the endothermic peaks and percentage weight loss, calculated from the TG curve, are shown. On the basis of the results of thermal and X-ray analysis the mechanisms of the thermal decomposition reaction were determined for nitritobismuthates(III).The thermal curves were used to calculate kinetic parameters, activation energy E_a and order of reaction n by Zsako's and Coats and Redfern's methods. A comparison of the thermal stabilities of the salts under study was made. Within the same group of nitritobismuthates(III), the activation energy and the decomposition temperatures of the salts increases when the difference between the radii of outer sphere cations increases.     

Thermal decomposition reactions of nickel(II) complexes under quasi-equilibrium conditions

The stoichiometry of thermal decomposition and thermal (thermodynamic) stability was studied for the Werner clathrates [Ni(4-Mepy)₄(NCS)₂]·G, whereG = benzene(I), toluene(II) andp-xylene(III). The loss of the volatile components occurs in five steps in compounds I and II and in four steps in the complex III. According to the quasi-equilibrium data the thermodynamic stability of these compounds can be ordered in the following sequence: I<II<III. The increasing host-guest interaction (larger positive band shift in the visible spectra) was accompanied by increasing in the quasi-equilibrium temperature (T _D) for the complexes under study.     

Synthesis, Characterization and thermal behaviour of hemimellitic acid complexes with lanthanides(III)

The complexes of lanthanides(III) with hemimellitic acid (1,2,3-benzenetricarboxylic acid, H₃btc) of the formula Ln(btc)·nH₂O, where Ln=lanthanide(III) ion and n=2?6 were prepared and characterized by elemental analysis, infrared spectra, X-ray diffraction patterns and thermal analysis. The IR spectra of the complexes indicate coordination of lanthanides(III) through all carboxylate groups. The complexes of La(III), Ce(III), Pr(III) and Er(III) are amorphous. On heating in air atmosphere all complexes lose water molecules and next anhydrous compounds decompose to corresponding metal oxides.     

Heterogeneous reactions of solid nickel(II) complexes XXIV

The Stoichiometry of thermal decomposition was studied for the following compounds: Ni(NCS)₂(pip)₄ (I), (pip=piperidine), Ni(NCS)₂(pip)₂py·H₂O (II), (py=piridine), Ni(NCS)₂(4-Mepip)₃ (III), Ni(NCS)₂(3-Mepip)₃ (IV) and Ni(NCS)₂(3.5-Me₂pip)₃ (V). In complexes I, II, III and IV the loss of the volatile ligands (on the TG curve to 300 °C) occurs in three steps and in complex V in two steps. The loss of the last molecules of volatile ligands is accompanied by the decomposition of NCS groups. Spectral data and magnetic moment values for the initial complexes I and II (together with the defined intermediates) indicated pseudooctahedral configuration while pentacoordination for complexes III, IV and V. Structural changes of the complexes studied in thermal decomposition reactions are discussed.     

Synthesis, spectroscopic, thermal characterization, and antimicrobial activity of miconazole drug and its metal complexes

Metal complexes having the general composition [MCl₂(H₂O)₂(L)₂]·yH₂O (where y?=?1?C3, M?=?Mn(II), Cu(II), Co(II), Ni(II), and Zn(II) and L?=?miconazole drug?=?MCNZ) and [MCl₂(H₂O)₂(L)₂]Cl·3H₂O (where M?=?Cr(III) and Fe(III)) have been synthesized. All the synthesized complexes were identified and confirmed by elemental analyses, IR, diffused reflectance, and thermal analyses (TG and DTA) techniques as well as molar conductivity and magnetic moment measurements. The molar conductance data reveals that bivalent metal complexes are non-electrolytes while Cr(III) and Fe(III) complexes are electrolytes and of 1:1 type. IR spectral studies reveal that MCNZ is coordinated to the metal ions in a neutral unidentate manner with N donor site of the imidazole-N. On the basis of magnetic and solid reflectance spectral studies, an octahedral geometry has been assigned for the complexes. Detailed studies of the thermal properties of the complexes were investigated by thermogravimetry (TG) and differential thermal analyses (DTA) techniques and the activation thermodynamic parameters are calculated using Coats?CRedfern method. The free MCNZ drug and its complexes were also evaluated against bacterial species (P. aeruginosa, S. aureus, B. subtilis, E. Coli) and fungi (A. fumigatus, P. italicum, and C. albicans) in vitro. The activity data show that the metal complexes have higher biological activity than the parent MCNZ drug.     

Thermal investigation and infrared evolved gas analysis of light lanthanide(III) complexes with pyridine-3,5-dicarboxylic acid

The characterisation of light lanthanide(III) complexes with pyridine-3,5-dicarboxylic acid of the formula Ln₂pdc₃·nH₂O where Ln denotes lanthanides from La to Gd, pdc = C₇H₅NO₄²⁻; n = 6 for Ce(III), n = 7 for Pr(III) and Sm(III), n = 8 for La and n = 13 for Nd(III), Eu(III) and Gd(III) was performed by the thermal analysis TG-DTA and the simultaneous infrared evolved gas analysis TG-FTIR. Heating of the crystalline complexes resulted in the dehydration process at first. Next, dehydrated compounds decompose releasing of CO₂, CO, CH₄ and hydrocarbons. Free pyridine molecules were detected only in the gaseous products of lanthanum(III) complex decomposition.     

Synthesis of several new lanthanide Glimepiride complexes for evaluation of microbial activity

The complexation between lanthanide metal ions like Nd(III), Tb(III), and Er(III) with Glimepiride produces 1: 1 molar ratio (metal: Glimepiride) monodentate complexes of general formula: [M(GMP)(H₂O)₄]Cl₃·xH₂O, where: M = Nd, Tb, and Er, x = 1, 10, respectively. The structures of obtained compounds were assigned by IR, ¹H NMR and UV/Vis spectra. Themogravimetric analysis and kinetic thermodynamic parameters have proved the thermal stability of Glimepiride complexes. Obtained lanthanide complexes showed significant effect against some bacteria and fungi.     

Crystal-structure refinement, thermal expansion, and chemical distortion of Bi2Ga4O9

Single crystals of Bi₂Ga₄O₉ are grown from a solution in a bismuth oxide melt. The structure (orthorhombic, space group Pbam, a = 7.918(2) Å, b = 8.299(2) Å, c = 5.894(2) Å, Z = 2) is refined to R = 0.052 in the anisotropic approximation based on single-crystal X-ray diffraction data. The structure is a framework. The bismuth(III) atoms are sixfold coordinated; gallium(III) exists in both tetrahedral and octahedral coordinations. The thermal expansion of Bi₂Ga₄O₉ is studied by high-temperature X-ray powder diffraction method and is found to be sharply anisotropic. A structural interpretation of the anisotropy is proposed. Chemical distortion in the Bi₂M₄O₉ compounds with M = Fe(III), Al, or Ga is analyzed and compared with the thermal expansion of Bi₂Ga₄O₉.     

Explosion evaluation and safety storage analyses of cumene hydroperoxide using various calorimeters

Plenty of thermal explosions and runaway reactions of cumene hydroperoxide (CHP) were described from 1981 to 2010 in Taiwan. Therefore, a thermal explosion accident of CHP in oxidation tower in 2010 in Taiwan was investigated because of piping breakage. In general, high concentration of CHP for thermal analysis using the calorimeter is dangerous. Therefore, a simulation method and a kinetic parameter were used to simulate thermal hazard of high concentrations of CHP only by the researcher. This study was applied to evaluate thermal hazard and to analyze storage parameters of 80 and 88 mass% CHP using three calorimeters for the oxidation tower, transportation, and 50-gallon drum. Differential scanning calorimetry (DSC) (a non-isothermal calorimeter), thermal activity monitor III (TAM III) (an isothermal calorimeter), and vent sizing package 2 (VSP2) (an adiabatic calorimeter) were employed to detect the exothermic behavior and runaway reaction model of 80 and 88 mass% CHP. Exothermic onset temperature (T ₀), heat of decomposition (ΔH _d), maximum temperature (T _max), time to maximum rate under isothermal condition (TMR_iso) (as an emergency response time), maximum pressure (P _max), maximum of self-heating rate ((dT/dt)_max), maximum of pressure rise rate ((dP/dt)_max), half-life time (t _1/2), reaction order (n), activation energy (E _a), frequency factor (A), etc., of 80 and 88 mass% CHP were applied to prevent thermal explosion and runaway reaction accident and to calculate the critical temperature (T _c). Experimental results displayed that the n of 80 and 88 mass% CHP was determined to be 0.5 and the E _a of 80 and 88 mass% CHP were evaluated to be 132 and 134 kJ mol^?1, respectively.     

Thermal decompositions of lanthanum and lanthanide salts of sebacic acid

The conditions of thermal decomposition of La, Ce(III), Pr(III), Nd, Sm(III), Eu, Gd, Tb(III), Dy, Ho, Er, Tm, Yb and Lu sebacates have been studied. When heated in air atmosphere, the sebacates of La and lanthanides with general formula Ln₂(C₁₀H₁₆O₄)₃·nH₂O, wheren=6?24, lose some crystallization water molecules in one or two steps at 323–343 K and are then dehydrated and decomposed simultaneously to the oxides Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇. The oxides are formed over the range of temperature 783 K (CeO₂)?1073 K (Nd₂O₃).     

New complexes of lanthanide Ln(III), (Ln = La, Sm, Gd, Er) with Schiff bases derived from 2-furaldehyde and phenylenediamines

Some new Schiff bases derivates from 2-furaldehyde and phenylenediamines (L^1-3) and their complexes with lanthanum (La), samarium (Sm), gadolinium (Gd) and erbium (Er) have been synthesized. These complexes with general formula [Ln(L^1-3)₂(NO₃)₂]NO₃·nH₂O (Ln = La, Sm, Gd, Er) were characterized by elemental analysis, UV-Vis, FT-IR and fluorescence spectroscopy, molar conductivity and thermal analysis. The metallic ions were found to be eight coordinated. The emission spectra of these complexes indicate the typical luminescence characteristics of the Sm(III), La(III), Er(III) and Gd(III) ions.     

Synthesis,spectral, antimicrobial,and thermal properties of Ce(III), Gd(III), Nd(III), Tb(III), and Er(III) gliclazide complexes

The complexation between the lanthanide metal ions Ce(III), Gd(III), Nd(III), Tb(III), and Er(III) and gliclazide produced 1 : 1 molar ratio metal: gliclazide (Glz) complexes coordinated in a monodentate fashion via the OH group and having the general formulas [M(Glz)Cl₃(H₂O)]·xH₂O (M = Ce, Gd, Nd and x = 1, 3, 4, respectively) and [M(Glz)(H₂O)₄]Cl₃·yH₂O (M = Tb, Er and y = 1, 2, respectively). The structure of the synthesized lanthanide gliclazide complexes was assigned by IR, ¹HNMR, and UV-Vis spectroscopy. Thermal analysis and kinetic and thermodynamic parameters gave evidence for the thermal stability of the Glz complexes. The latter showed a significant antimicrobial effect against some bacteria and fungi.     

Hydrothermal synthesis, thermal and luminescent investigations of lanthanide(III) coordination polymers based on the 4,4′-oxybis(benzoate) ligand

In this study, new series of lanthanide 4,4??-oxybis(benzoates) of the general formula Ln₂oba₃·nH₂O, where Ln = lanthanides from La(III) to Lu(III), oba?=?C₁₂H₈O(COO) ₂ ^2? and n?=?3?C6, has been prepared under hydrothermal conditions. The compounds were characterized by elemental analysis, infrared spectroscopy, X-ray diffraction patterns measurements and different methods of thermal analysis (TG, DSC, and TG-FTIR). In addition, photoluminescence properties of the selected complexes have been investigated. Crystalline compounds are isostructural in the whole series. Both carboxylate groups are deprotonated and engaged in the coordination of Ln(III) ions. Heating of the complexes leads to the dehydration and next decomposition processes. Although of the same structure, the removal of water molecules proceeds in different ways. In the nitrogen atmosphere, they decompose releasing water, carbon oxides and phenol molecules. The complexes of Eu(III), Tb(III) and Dy(III) exhibit photoluminescence in the visible range, whereas the compounds of Nd(III) and Yb(III) in the near-infrared region upon excitation by UV light.     

Evaluation of thermal hazard for lauroyl peroxide by VSP2 and TAM III

When above certain temperature limits, lauroyl peroxide is an unstable material. If the thermal source cannot be properly governed during any stage in the preparation, manufacturing process, storage or transport, runaway reactions may inevitably be induced immediately. In this study, the influence of runaway reactions on its basic thermal characteristic was assessed by evaluating thermokinetic parameters, such as activation energy (E _a) and frequency factor (A) by thermal activity monitor III (TAM III). This was achieved under five isothermal conditions of 50, 60, 70, 80, and 90?°C. Vent sizing package 2 (VSP2) was employed to determine the maximum pressure (P _max), maximum temperature (T _max ), maximum self-heating rate ((dT?dt ^?1)_max), maximum pressure rise rate ((dP?dt ^?1)_max), and isothermal time to maximum rate ((TMR)_iso) under the worst case. Results of this study will be provided to relevant plants for adopting best practices in emergency response or accident control.     

Thermal decomposition reactions of metal carboxylato complexes in the solid state: II. Thermographic and differential thermal studies of metal oxalato,malonato and succinato complexes

The thermal investigations of metal carboxylato complexes of the first transition metals, Mn(II), Fe(II), Fe(III), Co(II), Ni(II) and Cu(II) and non transition metals like Zn(II) and Cd(II) in solid state were carried out under non-isothermal condition in nitrogen atmopshere by thermogravimetric (TG) and differential thermal analyses (DTA) methods. The results of DTA curves inferred that the thermal stability of the complex decreased approximately with the increase of standard potential of the central metal ion. The thermal parameters like activation energy (E_a¹), enthalpy change (ΔH) and entropy change (ΔS) corresponding to deaquation, deammoniation and decomposition processes occurred simultaneously or separately were determined from TG and DTA curves by the standard methods. A linear correlation has been found in the plots of ΔH vs. ΔS and E_a¹ vs. ΔS in deaquation, deammoniation and decomposition processes. An irreversible phase transition was noticed for H₂[Mn(suc)₂] and H₂[Co(suc)₂] complexes in DTA curves. The residual pyrolysed products were metal carbonates.     

Synthesis,spectroscopic characterization and thermal studies of some rare earth metal complexes of unsymmetrical tetradentate Schiff base ligand

The solid complexes of La(III), Ce(III), Pr(III), Nd(III), Sm(III) and Gd(III) with 4-hydroxy-3-(1-{2-(2-hydroxy-benzylidene)-aminophenylimino}-thyl)-6-methy-pyran-2-one (H₂L) derived from o-phenylenediamine, 3-acetyl-6-methyl-(2H)pyran,2,4(3H)-dione (dehydroacetic acid or DHA) and salicylic aldehyde have been synthesized and characterized by elemental analysis, conductometry, magnetic susceptibility, UV–visible, FTIR, ¹H NMR spectra, X-ray diffraction, and thermal analysis and screened for antimicrobial activity. The FTIR spectral data suggest that the ligand behaves as a dibasic tetradentate ligand with ONNO donar atoms sequence towards central metal ion. From the microanalytical data, the stoichiometry of the complexes has been found to be 1:1 (metal:ligand). The physico-chemical data suggest distorted octahedral geometry for La(III), Ce(III), Pr(III), Nd(III), Sm(III) and Gd(III) complexes. The X-ray diffraction data suggest monoclinic crystal system for La(III) and Ce(III) and orthorhombic crystal system for Pr(III) and Nd(III) complexes. Thermal behaviour (TGA/DTA) of the complexes was studied and kinetic parameters were determined by Horowitz–Metzger and Coats–Redfern methods. The ligand and their metal complexes were screened for antibacterial activity against Staphylococcus aureus, Escherichia coli and Bacillus sp. Fungicidal activity against Aspergillus niger, Trichoderma and Fusarium oxysporum.     

ESR study of thermal destruction of polypyromellitimides

A mechanism for thermal degradation of poly-N, N′-[p, p′-diphenyl] -pyromellitimide(resin I), poly-N, N′-[(m, m′-dimethyl)-p,p′-diphenyl] pyromellitimide-(resin II), and poly-N, N′-[(m, m′-dimethoxy)-p, p′-diphenyl] pyromellitimide (resin III) has been studied by means of ESR spectroscopy and pyrolysis gas chromatography. The concentration of paramagnetic centres formed as a result of free-radical scission of C-C and C-N bonds and the parameters of the ESR signal (ΔH_max and g-value) are strictly dependent on temperature of resin decomposition. The results suggest quite different mechanisms for thermal destruction of resin III and that for the other two, namely formation of the benzoxazole ring as an intermediate stage in decomposition.     

Isothermal hazards evaluation of benzoyl peroxide mixed with benzoic acid via TAM III test

Isothermal microcalorimetry can be used to investigate the thermokinetic parameters for reactive mechanisms. Benzoyl peroxide (BPO), a typical organic peroxide, undergoes an autocatalytic reaction under isothermal decomposition. It requires intrinsically safer design of preparation, manufacturing, transportation, storage, and even disposal. The scope of this study was to describe the exothermic reaction and reaction model of BPO and mixed with benzoic acid by the thermal activity monitor III (TAM III). The results showed the isothermal kinetic parameters, such as activation energy (E _a), frequency factor (A), heat of decomposition (ΔH _d), and time to maximum rate under isothermal conditions (TMR _iso), which were necessary and useful to insure safe storage or transportation for self-reactive substances applied in the process industries.     

On the relationship between the structures of Cu(II) complexes and their chemical transformations

The thermal dehydration of pentacoordinate complexes [Cu(maleinate)(H₂O)] (I), [Cu₂(citrate) (H₂O)₂] (II) and [Cu(phenoxyacetate)₂(H₂O₃] (III) was investigated and correlated with the structural changes occurring during the dehydration. It was found that the activation parameters of the reactions do not follow the lengths of the split Cu?OH₂ bonds. The lowestE _a and lgA values were found for compound I, the highest ones for compound III. The most expressive changes of the anionic ligand binding mode take place during the dehydration of this compound.