Some Polynuclear Coordination Compounds Precursors of Chromites Synthesis,Physicochemical Characterization and Thermal Stability

The polynuclear coordination compounds LnCr(tartrate)₃·nH₂O where Ln(III)=La-Er, obtained through a precipitation method, were characterized on the basis of elemental analysis, their electronic and vibrational spectra and magnetic susceptibility measurements. The possibility of obtaining chromites through the transformations of the polynuclear coordination compounds in the solid state was considered. The thermal decompositions of these compounds, studied by TG and DTA methods, were found to follow an almost uniform pattern. The decompositions occurred in six-eight steps. The first two steps involved dehydration, and the third the transformation of tartrate anions to oxalate, followed by conversion to carbonate and oxocarbonate intermediates. The final product in each case was LnCrO₃. A non-isothermal kinetic analysis of the first decomposition steps was performed, the most probable decomposition mechanism being selected and the kinetic parameters evaluated. The final products of the transformations were characterized. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal Bevaviour of the Coordination Compound [Mn(urea)6](NO3)2·2H2O

Thermoanalytical, mass spectrometric and X-ray diffraction data were associated with a reliable assignation of the thermal transformations of the coordination compound [Mn(urea)₆](NO₃)₂·2H₂O. This revised version was published online in August 2006 with corrections to the Cover Date.     

The synthesis of manganese-zinc ferrite through the transformation of polynuclear coordination compounds

The authors analyse the possibility of obtaining manganese-zinc ferrite through the transformations of polynuclear coordination compounds (pcc), either in the solid state or in a reaction medium. Polynuclear coordination compound precursors with the general molecular formula: [Fe(II)_xFe(III)_y(Mn_0.5Zn_0.5)(C₂O₄)₂(OH)_y+2(H₂O)₂] with 0.2相似文献   

Synthesis of cadmium complex sulfides nanoparticles by thermal decomposition

Summary The paper presents the conditions of synthesis and results in the characterization (chemical analysis, thermal analysis, kinetic of decomposition) for two complex compounds of cadmium: [Cd(S₂O₃)phen]×H₂O and [Cd(S₂O₃)phen₂]×2H₂O. The obtained complexes were used as precursors for complex sulfides by controlled thermal decomposition. On the basis of transmission electron microscopy (TEM) the complex sulfides may be included in the nanomaterials category.     

Thermal Stability of Some Polynuclear Coordination Compounds in the Systems Ln(III)—Co(II)—Oxalate

This paper reports an investigation of the thermal stabilities of the class of coordination compounds containing lanthanide ions Ln(III) (Ln=La, Sm, Eu, Dy, Er), Co(II) ions and oxalate anions C₂O ₄ ^2– . The thermal decomposition steps were identified, and in some cases the values of the non-isothermal kinetic parameters were determined.This revised version was published online in November 2005 with corrections to the Cover Date.     

Non-Conventional Methods for Obtaining Hexaferrites Thermal Analysis of Some Precursors

Bd. Republicii, Nr. 13, sector 2, Bucharest The thermal behaviour of the polynuclear coordination compounds [Fe_12?xSr(malic)_19?1.5x]·18H₂O and [Fe_12?xSr(gluc)_19?1.5x]·20H₂O precursors of strontium hexaferrite was investigated, and a decomposition mechanism is proposed. A pure hexaferrite with a mean crystallite size value of about 250 Å was obtained after 5 h calcination at 800°C of the gluconic precursor (x=1.5).     

Nonconventional methods for obtaining hexaferrites

Small particles of PbFe₁₂O₁₉ have been synthesized. X-ray diffraction, thermal analysis and magnetic investigations have been conducted in order to obtain information on the mechanism of lead hexaferrite formation.Dedicated to Prof. Menachem Steinberg on the occasion of his 65th birthday     

On the thermal stability of some polynuclear coordination compounds of Ni(II) and Fe(III) generating nickel ferrite

The authors present their results concerning the thermal conversion of some polynuclear coordination compounds of Ni(II) and Fe(III) into nickel ferrite.     

Copper-iron oxides obtained by thermal decomposition of oxalic coordination compounds

The influence of the coordination architecture (materialized by ligand binding mode and content) on the thermal behaviour of coordination compounds containing copper, iron and oxalic anion as ligand was investigated. It was established that the metal-metal connections influence stronger, comparative with ligand content, the stoichiometry of the thermal decompositions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal stability and non-isothermal decomposition kinetics of a polynuclear coordination compound precursor of copper ferrite

Results are presented on the thermal behaviour of [Fe(III)₂Cu(C₂C₄)₂(OH)₄(H₂O)₂] precursor of copper ferrite. An investigation of the decomposition steps and intermediates was followed by a non-isothermal kinetic analysis of the processable steps.