Thermal behaviour of malonic acid,sodium malonate and its compounds with some bivalent transition metal ions

Characterization, thermal stability and thermal decomposition of transition metal malonates, MCH₂C₂O₄·nH₂O (M = Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II)), as well as, the thermal behaviour of malonic acid (C₃H₄O₄) and its sodium salt (Na₂CH₂C₂O₄·H₂O) were investigated employing simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), infrared spectroscopy, TG-FTIR system, elemental analysis and complexometry. The dehydration, as well as, the thermal decomposition of the anhydrous compounds occurs in a single step. For the sodium malonate the final residue up to 700 °C is sodium carbonate, while the transition metal malonates the final residue up to 335 °C (Mn), 400 °C (Fe), 340 °C (Co), 350 °C (Ni), 520 °C (Cu) and 450 °C (Zn) is Mn₃O₄, Fe₂O₃, Co₃O₄, NiO, CuO and ZnO, respectively. The results also provided information concerning the ligand's denticity, thermal behaviour and identification of some gaseous products evolved during the thermal decomposition of these compounds.     

Thermal and spectroscopic data to investigate the oxamic acid,sodium oxamate and its compounds with some bivalent transition metal ions

Synthesis, characterization, and thermal behavior of transition metal oxamates, M(NH₂C₂O₃)₂·nH₂O (M = Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II)), as well as the thermal behavior of oxamic acid and its sodium salt (NaNH₂C₂O₃) were investigated employing simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC), experimental and theoretical infrared spectroscopy, TG-DSC coupled to FTIR, elemental analysis and complexometry. The results led to information about the composition, dehydration, thermal stability, thermal decomposition, as well as of the gaseous products evolved during the thermal decomposition of these compounds in dynamic air and N₂ atmospheres.     

Thermal investigation of solid 2-methoxycinnamylidenepyruvate of some bivalent transition metal ions

Solid-state M-2-MeO-CP compounds, where M represents bivalent Mn, Fe, Co, Ni, Cu, Zn and 2-MeO-CP is 2-methoxycinnamylidenepyruvate, were synthesized for the first time. Simultaneous thermogravimetry and differential thermal analysis, differential scanning calorimetry, X-ray powder diffractometry, infrared spectroscopy, TG-FTIR system, elemental analysis and complexometry have been used to characterize and to study the thermal behaviour of the compounds. The dehydration in all the compounds, except for iron occurs in a single step. The thermal decomposition of the anhydrous compounds occurs in two or three steps with the formation of the respective oxides, Mn₃O₄, Fe₂O₃, Co₃O₄, NiO, CuO and ZnO, as final residue. The results also provided information concerning the thermal behaviour and identification of the gaseous products evolved during the heating of these 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.     

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.     

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

Solid-state M-2-Cl-BP, where M stands for Mn, Fe, Co, Ni, Cu, Zn and Pb and 2-Cl-BP is 2-chlorobenzylidenepyruvate, have been synthesized. Thermogravimetry and derivative thermogravimetry (TG/DTG), simultaneous thermogravimetry and differential thermal analysis (TG-DTA), X-ray powder diffractometry, infrared spectroscopy, elemental analysis, and complexometry were used to characterize 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 compounds.     

Thermal studies on 2,6-xylyliminodiacetato compounds of some transition metal ions

Some new 2,6-xylyliminodiacetato compounds of Mn(II), Fe(III), Ni(III), Zn(II) and Cd(II) have been prepared in aqueous media. The thermal behaviour of these compounds has been studied by TG, DTG, and DSC techniques. Heats of dehydration have been calculated from the DSC curves.     

Thermal behavior of some compounds of methanesulfonic acid with transition metals

The following compounds of methanesulfonic acid, CH₃SO₃H, have been prepared: Cu(CH₃SO₃)₂ · 4 H₂O; Zn(CH₃SO₃)₂ · 4 H₂O; Mn(CH₃SO₃)₂ · 2 H₂O; Cd(CH₃SO₃)₂ · 2 H₂O and Ag(CH₃SO₃). Their thermal behavior has been studied using TG and DTA, together with X-ray analysis of the solid products formed during the heating. The water of hydration is evolved in one step (Mn, Cd) or in two step (Cu, Zn). The intermediate hydrates and the anhydrous salts are crystallized. The anhydrous Zn, Ag and Cd compounds melt, the anhydrous Cd salt undergoing a polymorphic transition before melting. They then begin to decompose in the temperature range 325–440°C. Under an inert atmosphere, the decomposition yields well-crystallized residues of various composition: Cu + Cu₂S; Ag + Ag₂S (the sulfides being in very minute amounts); MnS; CdS; ZnO + ZnS.     

Thermal and electrical studies on quinoxaline compounds of some first row transition metal ions

The chloro and bromo compounds of quinoxaline with manganese(II), cobalt(II), nickel(II) and copper(II) have been prepared in ethanolic solution. The thermal behaviour of these compounds was studied by thermogravimetry (TG) and differential thermal analysis (DTA). The thermal decomposition studies show that the compounds dichlorobis(quinoxaline) cobalt(II), dibromobis(quinoxaline) cobalt(II) and dibromobis(quinoxaline) manganese(II) form intermediate compounds before the metal halide is produced. The other compounds undergo decomposition with loss of organic ligand and the formation of the metal halide. Electrical conductivities at room temperature range from 1.4 × 10⁻⁶ Ω⁻¹ m⁻¹ for MnCl₂Q to 2.3 × 10⁻³ Ω⁻¹ m⁻¹ for both CoCl₂Q₂ and CoBr₂Q₂. There appears to be a correlation between electrical conductivity and coordination number of the metal atom. From the temperature dependence of conductivity, information has been obtained for donor or acceptor ionization energies. Decomposition temperature, as electrically determined, is in good agreement with the TG method.     

Synthesis, characterization and thermal behaviour of solid-state compounds of folates with some bivalent transition metals ions

Solid-state M–L compounds, where M stands for bivalent Mn, Co, Ni, Cu and Zn and L is folate (C₁₉H₁₇N₇O₆)_, have been synthesized. Simultaneous thermogravimetry and differential scanning calorimetry (TG–DSC), X-ray powder diffractometry, infrared spectroscopy (FTIR), TG–DSC coupled to FTIR, elemental analysis and high-resolution continuum source flame atomic absorption spectrometry technique (HR-CS FAAS) were used to characterize and to study the thermal behaviour of these compounds. The results provided information concerning the composition, dehydration, thermal stability and thermal decomposition.     

Synthesis, characterization and thermal study of solid mandelate of some bivalent transition metal ions in CO2 and N2 atmospheres

Solid state M-L, where M stands for bivalent transition metals (Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II)) and L is mandelate, were synthesized. Simultaneous thermogravimetry and differential scanning calorimetry, elemental analysis and complexometry were used to establish the stoichiometry and to study the thermal behaviour of these compounds in CO₂ and N₂ atmospheres. The results show that all the compounds were obtained in the anhydrous state and in agreement with the general formula ML₂. The thermal decomposition of the compounds occurs in a single (Cu(II)), two (Ni(II)) three (Fe(II), Co(II)), four (Mn(II)) and five (Zn(II)) steps. The results also provided information concerning the ligand’s denticity, thermal behaviour, final residues and identification of gaseous products evolved during the thermal decomposition of these compounds.     

Spectrophotometric studies,stability constants and thermodynamics for complexes ofo-hydroxyacetophenone isobutyroylhydrazone with some bivalent transition metal ions

Summary The u.v. spectra ofo-hydroxyacetophenone isobutyroylhydrazone (HAIBuH) were investigated in pure organic solvents as well as in Britton Robinson buffer solutions of varyingpH values. The interaction ofHAIBuH with Co(II), Ni(II) and Cu(II) were studied spectrophotometrically. The optimumpH favouring the formation of the highly coloured complexes are 8.5, 8.0 and 7.5 for Co(II), Ni(II) and Cu(II), respectively. The stoichiometries of these complexes were determined and indicated the formation of 1:2 (metal:ligand) complexes of Co(II) and Ni(II) and a 1:1 complex of Cu(II). The dissociation constantspK ^H ofHAIBuH and the overall stability constants log of their complexes were determined at different temperatures (293, 303 and 313 K). The corresponding thermodynamic parameters (G, H and S) in 20% (v/v) ethanol-water mixture were derived and discussed.

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Spektrophotometrische Untersuchungen, Stabilitätskonstanten und Thermodynamik der Komplexe vono-Hydroxyacetophenonisobutyroylhydrazon mit einigen bivalenten Übergangsmetallionen

Zusammenfassung Die UV-Spektren vono-Hydroxyacetophenon-isobutyroylhydrazon (HAIBuH) wurden in reinen organischen Solventien und in Britton-Robinson-Pufferlösungen von verschiedenempH gemessen. Die Wechselwirkung vonHAIBuH mit Co(II), Ni(II) und Cu(II) wurde spektrophotometrisch untersucht. Die optimalenpH-Werte zur maximalen Ausbildung der starkgefärbten Komplexe sind 8.5, 8.0 bzw. 7.5 für Co(II), Ni(II) bzw. Cu(II). Für die Stöchiometrien wurde ein Metall: Ligand-Verhältnis 1:2 für Co(II) und Ni(II) und 1:1 für Cu(II) bestimmt. Die DissoziationskonstantenpK ^H vonHAIBuH und die Gesamtstabilitätskonstanten log der Komplexe wurden bei verschiedenen Temperature bestimmt (293, 303 und 313 K) und die entsprechenden thermodynamischen Parameter (G, H und S) in 20% (v/v) Ethanol-Wasser-Mischung errechnet und diskutiert.

     

Chelating behavior, thermal studies and biocidal efficiency of tioconazole and its complexes with some transition metal ions

New seven metal complexes of tioconazole drug with the general formulae [MCl₂(L)₂(H₂O)_x].yH₂O (where, x = 0 and y = 1 for M = Mn(II) or x = 2, y = 2 for M = Co(II)), and x = 0, y = 3 for M = Cu(II), Ni(II), Zn(II)) and [MCl₂(L)₂(H₂O)₂]Cl.3H₂O (where M = Cr(III) and Fe(III)) have been prepared and characterized based on elemental analyses, IR, magnetic moment, molar conductance, and thermal analyses techniques. From molar conductance data bivalent metal chelates are non-electrolytes while Cr(III) and Fe(III) chelates are electrolytes and of 1:1 type. According to the IR spectral data, TCNZ is coordinated to the metal ions in a neutral unidentate manner with N donor site of the imidazole–N. All the complexes are octahedral except Mn(II) complex has tetrahedral structure. TCNZ drug and its metal complexes were also screened for their biological activity.     

Studies on 2-aminobenzophenone-2-thenolhydrazone complexes of some bivalent transition metal ions

Summary Complexes having the chemical compositions [VO(Habth)₂SO₄], [M(Habth)₂Cl₂] [M=Co^II, Ni^II, Cu^II or Zn^II) and [M(abth)₂] [M=V^IVO, Co^II, Ni^II, Cu^II or Zn^II) and Habth=2-aminobenzophenone-2-thenoylhydrazone] have been prepared and characterized. The complexes are non-electrolytes. Magnetic moments and electronic, photoacoustic, e.s.r. and i.r. spectra of the complexes are used to establish the stereochemistry and mode of bonding of the hydrazone.     

The Jahn-Teller effect in solid state chemistry of transition metal compounds

The general features of the local and cooperative Jahn-Teller effect of dⁿ cations with E_g ground states in octahedral coordination and simple model structures are discussed. Examples of different cooperative Jahn-Teller ordering patterns and of phase transitions from static to partially dynamic and finally fully dynamic Jahn-Teller determined structures are given. While in general a tetragonally elongated coordination of the Jahn-Teller ions is favored, the compressed configuration may be stabilized under certain conditions also. It is demonstrated by some examples that the extent of the Jahn-Teller distortion depends on the symmetry and connection pattern of the polyhedra in the host lattice structure. Finally it is shown that the crossover between high- and low-spin configurations of d⁷ cations is strongly influenced by the additional Jahn-Teller stabilization of the low-spin ²E_g state.     

Binary,ternary and quaternary complexes invloved in the systems pyridoxamine-glycine-imidazole with some bivalent metal ions

Equilibrium-based computer models using MINIQUAD-75 program were utilized to determine the stoichiometry and formation constants involved in the systems pyridoxamine(Pm)-glycine (Gly)-imidazole (lmd) with CO(II), Ni(II), Cu(II), Zn(II) and Cd(II) metal ions. The data were obtained from potentiometric pH titration of the various binary and ternary quaternary systems under physiological-like conditions (0.15 M NaNO₃-37°C). Various composition ratios of metal and ligands were used. The ligand concentrations did not exceed 4 times the concentration of metal ion in the binary systems and 4 times of the metal ions in ternary systems. In case of the quaternary systems only imidazole concentrations were two or four times the concentrations of metal ions keeping those of other ligands equal to that of metal ions. The stability constants of the quaternary species are discussed in terms of binary and ternary constants as are the effect of ring size on the stability of mixed ligand species. In addition, electrostatic as well as statistical effects also are mentioned and the biological implications of these model equilibria are described.     

Thermal properties of some complexes of quinolinic acid with divalent metal ions

Studies of the complexes of pyridinecarboxylic acids with divalent metal ions as a function of the position of the carboxyl groups were extended. The thermal properties of the complexes of quinoline acid (pyridine-2,3-dicarboxylic acid) with several divalent metal ions were determined by thermogravimetry (TG) and differential thermal analysis (DTA). A correlation between these compounds and others obtained by reaction between the studied metal ions with similar acids (lutidinic acid (pyridine-2,4-dicarboxylic acid) and isocinchomeronic acid (pyridine-2,5-di-carboxylic acid) is discussed in terms of the position of the carboxyl group far from the aza group. The thermal stability of the metal complexes is in the order Mn(II) > Fe(II) > Zn(II) ? Co(II) > Ni(II) > Cu(II).     

Thermochemistry of adducts of some bivalent transition metal bromides with aniline

The compounds [MBr₂(an)₂] (where M is Mn(II), Fe(II), Co(II), Ni(II), Cu(II) or Zn(II); an = aniline) were synthesized and characterized by melting points, elemental analysis, thermal studies, and electronic and IR spectroscopy. The enthalpies of dissolution of the adducts, metal(II) bromides and aniline in methanol, aqueous 1.2 M HCl or 25% (v/v) aqueous 1.2 M HCl in methanol were measured. The following thermochemical parameters for the adducts have been determined by thermochemical cycles: the standard enthalpies for the Lewis acid/base reactions (Δ_rH°), the standard enthalpies of formation (Δ_fH°), the standard enthalpies of decomposition (Δ_DH°), the lattice standard enthalpies (Δ_MH°) and the standard enthalpies of the Lewis acid/base reactions in the gaseous phase (Δ_rH°(g)). The mean bond dissociation enthalpies of the M(II)-nitrogen bonds () and the enthalpies of formation of the adducts from the ions in the gaseous phase: M²⁺_(g) + Br⁻_(g) + an_(g) → [MBr₂(an)₂]_(g), (Δ_fiH°) have been estimated.