Thermal studies on beryllium titanyl/zirconyl oxalates

Beryllium titanyl oxalate tetrahydrate and beryllium zirconyl oxalate tetrahydrate were prepared in aqueous medium and characterized by elemental analyses, magnetic susceptibility measurements and IR spectral studies. The thermal behaviour of these compounds under non-isothermal conditions was investigated by thermogravimetric, derivative thermogravimetric and differential scanning calorimetric (DSC) techniques. The intermediates obtained at the end of the various thermal decomposition steps were identified on the basis of elemental analyses and IR spectral studies. The decomposition proceeds through three major steps, viz, dehydration of the hydrate, decomposition of the oxalate to carbonate and decomposition of the carbonate to oxide. The graphical method of Coats and Redfern was employed to calculate kinetic parameters such as apparent activation energy and order of reaction. Heats of reaction for the different decomposition steps were calculated from the DSC curves.     

Thermal decomposition of manganese(II)bis(oxalato)nickelate(II)tetrahydrate

Summary A mixed metal oxalate, manganese(II)bis(oxalato)nickelate(II)tetrahydrate, has been synthesized and characterized by elemental analysis, IR spectral and X-ray powder diffraction (XRD) studies. Thermal decomposition studies (TG, DTG and DTA) in air showed that the compound decomposed mainly to Mn₂O₃, MnO₂ and NiO at ca.1000°C, via. the formation of several intermediates. DSC study in nitrogen upto 500°C showed the endothermic decomposition. The tentative mechanism for the thermal decomposition in air is proposed.     

Infrared and thermal studies of strontium zirconyl oxalate hexahydrate

Strontium zirconyl oxalate hexahydrate (SZO) is prepared and characterized by chemical analysis and IR spectral studies. Its thermal decomposition studies have been made using thermogravimetry (TG) and differential thermal analysis (DTA). The decomposition has been found to proceed through three major steps (i) a three stage dehydration, (ii) decomposition of the oxalate and (iii) decomposition of carbonate to strontium zirconate. Carbon dioxide is found to be trapped in the solid during the decomposition of the oxalate. The identification of residues at various stages has been done by IR spectra and chemical analysis.     

Correlation of thermal and spectral properties of chromium(III) picolinate complex and kinetic study of its thermal degradation

Chromium(III) picolinate complex, namely [Cr(pic)₃]·H₂O, was prepared and characterized by the methods of the elemental analysis, infrared spectroscopy, X-ray diffraction, and thermal analysis (TG/DTG, DTA). The correlation of the thermal and spectral properties of the complex with its structure is discussed in the study. The correlation of the spectral data with the structure leads to the accord, and coherence was found between thermal properties and structure of the complex for both steps of the thermal decomposition (dehydration and pyrolysis of organic ligand). Activation parameters were evaluated using the theory of absolute reaction rate.     

Thermoanalytical study of heavier trivalent lanthanides fumarates

Solid-state heavier lanthanides fumarates compounds have been synthesized, and the compounds were characterized by employing simultaneous thermogravimetry and differential thermal analysis (TG–DTA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), TG coupled to FTIR, elemental analysis, and complexometry. On heating, the dehydration occurs in a single and two consecutive steps and the thermal decomposition of the anhydrous compounds occurs in consecutive and/or overlapping steps, with formation of the respective oxides: Tb₄O₇ and Ln₂O₃ (Ln=Dy to Lu). The results also led to information about composition, thermal behavior, and the type of coordination of the isolated compounds.     

Kinetic study of the multistep thermal behaviour of barium titanyl oxalate prepared via chemical precipitation method

This study describes the physico-geometrical mechanism and overall kinetics for the multistep thermal dehydration of barium titanyl oxalate tetrahydrate (BTO). The thermal dehydration kinetics of BTO was studied at four different linear heating rates under non-isothermal conditions. The reaction kinetics was performed using differential scanning calorimetry (DSC) and the curves obtained were analysed using different isoconversional model-free equations and the values are found to be compatible with each other. The kinetic deconvolution principle is used for identifying the partially overlapped kinetic processes of the thermal dehydration of BTO, and it occurs in two stages. The overall reaction kinetics parameters calculated via kinetic deconvolution of the sample indicate the multistep nature of the process and the kinetic analysis of the non-isothermal data of this reaction model shows that the reaction is best described by Sestak–Berggren (m, n) empirical kinetic model. The prepared sample was identified and characterized by means of FT-IR, XRD, SEM, and TEM.

     

Synthesis and spectrothermal studies on group 12 metals coordination with novel carboxyamide ligands

Complexes of group 12 metals with new ligands N',N'-bis(3-carboxy-1-oxopropanyl) 2-amino-N-arylbenzamidine (H2L) and N',N'-bis(3-carboxy-1-oxophenelenyl) 2-amino-N-arylbenzamidine (H(2)L) have been synthesized and characterized by elemental analyses, vibrational spectra, electronic spectra, (1)H NMR spectra, TOF-mass spectra, thermal studies and molecular modeling studies. The infrared and (1)H NMR spectral data are in agreement with coordination of amide and carboxylate oxygen of the ligands giving a MO(4) tetrahedral chromophore. The elemental analyses and mass spectral data have justified the ML complexes. The thermal behaviour of complexes shows that water molecule is removed in first step--followed by decomposition of the rest of the molecule in the next steps. Kinetic and thermodynamic parameters were computed from the thermal data using Coats and Redfern method, which confirm first order kinetics. Molecular structures of the complexes have been optimized by MM2 calculations and supported tetrahedral geometry around metal(II) ions.     

Pyrolysis of Nickel Zirconyl Oxalate

Nickel zirconyl oxalate hexahydrate (NiZrOx) is δ prepared and characterised by I.R. spectral and chemical analysis. Its thermal decomposition has been investigated by employing TG, DTG, DTA and chemical analysis. End product was identified by X-ray diffraction studies. The decomposition proceeds through four steps i) dehydration of NiZrOx in two steps, ii) partial decomposition of oxalate to give an oxalate carbonate intermediate, iii) decomposition of oxalate to give a non-stoichiometric carbonate and iv) decomposition of this non-stoichiometric carbonate to give the end product a mixture of NiO+ZrO₂. On the basis of the results obtained, a tentative scheme for the decomposition of NiZrOx is proposed.     

On the nature of isomerism in oxalatecopper(II) diammine thermal decomposition of α-, β-, and γ-Cu(C2O4)(NH3)2

The mechanisms of the thermal decompositions of various isomers of Cu(C₂O₄)-(NH₃)₂ were studied in this work. Data were obtained by the DSC technique and Derivatograph as well as infrared spectra and chemical analysis. The destruction of the complexes was found to take place in three steps—the first two of them being endothermic, and the third one exothermic. The values of ΔH₁, apparent activation energy and stoichiometry of the first step of destruction suggest that certain differences in bonding of the oxalate groups in each isomer lead to quite significant differences in their thermal decomposition.     

Multifunctional materials based on polyazomethines derived from 2,5‐dihydroxy‐1,4‐benzoquinone and siloxane diamines

New polyazomethines have been synthesized by the reaction between 2,5‐dihydroxy‐1,4‐benzoquinone and siloxane diamines differing by the siloxane sequence length. A dimer has also been prepared as a model compound. The products were characterized by spectral (FTIR and ¹H‐NMR) and elemental analyses, GPC, viscosity measurements, solubility tests, and transmission electron microscopy (TEM). The different properties have been investigated by adequate techniques: thermal (DSC and TGA), spectral (UV–vis and fluorescence spectroscopy), redox (Differential Pulse Voltammetry). pH‐sensitivity and metal complexing ability were also evaluated. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1862–1872, 2008     

Solid-state compounds of 2-methoxybenzylidenepyruvate with some bivalent metal ions

Solid-state M-2-MeO-BP compounds, where M represents bivalent Mn, Fe, Co, Ni, Cu, Zn and 2-MeO-BP is 2-methoxybenzylidenepyruvate have been synthesized. Simultaneous thermogravimetry-differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, infrared spectroscopy, elemental analysis and complexometry were used to characterize and to study the thermal stability and thermal decomposition of these compounds. The results led to information about the composition, dehydration, crystallinity and thermal decomposition of the isolated compounds.     

Synthesis, characterisation and thermal behaviour of solid state compounds of 4-methylbenzylidenepyruvate with some bivalent metal ions

Solid state M-4-Me-BP compounds, where M stands for bivalent Mn, Fe, Co, Ni, Cu, Zn, Pb and 4-Me-BP is 4-methylbenzylidenepyruvate, have been synthesized. Simultaneous thermogravimetry-differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, infrared spectroscopy, elemental analysis, and complexometry were used to characterise and to study the thermal behaviour of these compounds. The results led to information about the composition, dehydration, thermal stability and thermal decomposition of the isolated complexes.     

Thermolysis of hydrogen sulphate,nitrate and perchlorate salts of diphenylamine. Part LXVIII

Hydrogen sulphate, nitrate and perchlorate salts of diphenylamine have been prepared and characterized by elemental, spectral and gravimetric analyses. Thermal decomposition of these salts has been evaluated by TG (static air) and DSC (inert atmosphere). The proton transfer reaction plays a major role during thermolysis of these salts. The diphenylammonium hydrogen sulphate under thermal and microwave irradiation forms 4-(phenylamino) benzenesulphonic acid by sulphonation process, whereas nitrate and perchlorate salts do not form corresponding nitro and perchloro derivatives, rather they ignite and explode, respectively, to form gaseous products along with a residual carbon .     

Non-template synthesis of ‘N4’ di- and tetra-amide macrocylic ligands with variable ring sizes

Nine new macrocyclic ligands containing two- or four-amide groups have been prepared by the cyclization reaction of three different diamines with acid chlorides (oxalyl dichloride or malonyl dichloride), diesters (diethyl oxalate or diethyl malonate) or 1,2-dichloroethane. The macrocycles prepared are four tetraaza-14-crown-4, four tetraaza-15-crown-4 and one tetraaza-16-crown-4. All the macrocyclic ligands were characterized by elemental analysis and, IR, UV, NMR and mass spectral investigations.     

Synthesis,characterization and thermal behaviour of solid-state 3-methoxybenzoates of heavy trivalent lanthanides and yttrium(III)

Solid-state Ln(L)₃ compounds, where Ln stands for trivalent Tb, Dy, Ho, Er, Tm, Yb, Lu and Y, and L is 3-methoxybenzoate, have been synthesized. X-ray powder diffractometry, infrared spectroscopy, complexometry and elemental analysis were used to characterize the compounds. In order to study the thermal behaviour of these compounds simultaneous thermogravimetry and differential thermal analysis (TG-DTA) and differential scanning calorimetry (DSC) were used. The results provided information on the composition, dehydration, polymorphic transformation, thermal stability and thermal decomposition of the synthesized compounds.     

Thermal studies on alkaline earth monomethyl violurates

Some alkaline earth monomethyl violurate hexahydrates were prepared in aqueous medium, and characterized on the basis of elemental analysis and IR spectral data. The thermal behaviour of these salts was studied with the aid of TG, DTG and DSC techniques. Heats of dehydration were calculated from DSC curves.     

An investigation on solid-state pyrolytic decomposition of barium trihemiaquatris(oxalato)lanthanate(III)decahydrate using TG–DTA in air and DSC in nitrogen

A heterobimetallic oxalate coordination compound, barium(II)trihemiaquatris(oxalato)lanthanate(III)decahydrate, has been synthesized and characterized by elemental analysis, IR and electronic spectral studies. Crystalline nature of the compound with orthorhombic symmetry is corroborated from powder X-ray diffraction studies. The solid-state pyrolytic decomposition studies (TG, DTG and DTA) in air showed that the compound decomposed mainly to BaO, La₂O₃ and BaLa₂O₄ along with carbides of both the metal at ca. 1,000 °C through a number of intermediate steps. The DSC studies in nitrogen up to 670 °C found that the compound crumbled through several endothermic and one exothermic processes. The kinetic parameters, E*, lnk _o, ΔH ^# and ΔS ^# of dehydration and decomposition steps in nitrogen are evaluated from DSC peaks and discussed.     

Synthesis, thermal and calorimetric investigations of cobalt(ii) trihydrogen hexaoxoperiodate tetrahydrate

A new cobalt(II) trihydrogen hexaoxoperiodate tetrahydrate has been synthesized: CoH₃IO₆·4H₂O and has been characterized by quantitative analysis, TG, DTA, DSC and IR spectroscopy. Based on DTA and DSC data, a thermal decomposition scheme has been proposed for this complex.     

Solid-state thermal decomposition of heterobimetallic oxalate coordination compounds, zinc(II)tetraaquatris(oxalato)lanthanate(III)hexahydrate and cadmium(II)heptaaquatris(oxalato)lanthanate(III)tetrahydrate

Two heterobimetallic oxalate coordination compounds, zinc(II)tetraaquatris(oxalato)lanthanate(III)hexahydrate (ZnOLa) and cadmium(II)heptaaquatris(oxalato)lanthanate(III)tetrahydrate (CdOLa) were synthesized and characterized by elemental analysis, IR, electronic spectral and powder X-ray diffraction studies. Both the compounds were found to have monoclinic structure. Thermal decomposition studies by TG, DTG and DTA in air have proved that the aqua ligands are associated with metals in a stronger coordination mode. The temperatures for pyrolysis were adopted from the TG results chosen from the stable range of thermograms. In case of ZnOLa, it decomposes through two steps and the end product at 1000 °C was found to be consisting of mainly, La₂O_3, ZnO and La₂ZnO _x through the intermediate formation of several oxycarbonates of lanthanum at ca. 525 °C. In case of cadmium analogue, three steps decomposition were observed and the final products were confirmed as CdO₂, La₂O₃, LaCO and La₂CdO _x via the formation of several intermediates at 340 and 590 °C. The La₂C₃ and carbon are also found as part of the end product. The kinetic parameters, E ^*, lnk _o, ?H ^# and ?S ^# of all the deaquated and decomposition steps are investigated and discussed from the DSC study in nitrogen.     

Studies on the thermal behaviour of mono- and di-imines of some diaminonaphthalenes

The mono- and di-imines of some diaminonaphthalenes were prepared using a solid solid reaction technique. Their structures were studied using elemental analysis, infrared and electronic spectra. The thermal behaviour of the obtained compounds and their solid solid preparation reactions have also been studied. The energies of activation as well as the reaction orders of those reactions were determined.