Thermal behaviour of the homopolynuclear glyoxylate complex combinations with Cu(II) and Cr(III)

Homopolynuclear complexes of Cu(II) respectively Cr(III) with the glyoxylate dianion, C₂H₂O₄ ^2-, have been studied in non-isothermal regime in air and nitrogen. The results of the non-isothermal analysis performed for the synthesised complexes, Cu(C₂H₂O₄)·0.5H₂O, respectively [Cr₂(OH)₂(C₂H₂O₄)₂(OH₂)₄]·2H₂O, correlated with the results of the IR and TG analysis of the compounds obtained by thermal treatment from the initial complexes and the results of the GLC and XR analysis have led to the establishment of the thermal decomposition mechanisms for the two studied complexes. The decomposition mechanisms confirm the stoichiometric and structural formulae proposed for the two synthesised homopolynuclear complexes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of the amine type on thermal stability of modified mesoporous silica used for CO2 adsorption

In this study, the preparation by grafting of amino-functionalized SBA-15 molecular sieves was carried out. Amino-functionalized molecular sieves were synthesized using a silane coupling agent and different types of amination reagents which react with modified SBA-15. These composites were characterized by FT-IR spectroscopy, X-ray diffraction at low angles, nitrogen physisorption at 77 K, and evaluated by the adsorption of CO₂ and its temperature-programmed desorption—TPD. Thermal stability was investigated by TGA and DTA methods. In the view of a possible use of these amino-functionalized molecular sieves as sorbents for CO₂ removal, their adsorption–desorption properties towards CO₂ were also investigated by the TPD method. The mass loss of amino-functionalized molecular sieves above 215 °C was due to the oxidation and decomposition of amino propyl functional groups. This means that these composites could be used for adsorption of CO₂ at temperatures below 215 °C. The adsorption of CO₂ and its temperature programmed desorption using thermogravimetry were studied for amino-functionalized molecular sieves at 60 °C. The evolved gases during the adsorption–desorption of CO₂ on amino-functionalized molecular sieves were identified by online mass spectrometry coupled with thermogravimetry. CO₂ adsorption isotherms of functionalized samples at 60 °C showed that both the adsorption capacity (mg CO₂/g adsorbent) and the efficiency of amino groups (mol CO₂/mol NH₂) depend on the type of amination reagents and the amount of organic compound used.

     

Synthesis, thermal behavior, and spectral properties of mixed-metal Cu(I)-VO(IV)-thiourea coordination polymers

Abstract  

The heterometallic complexes [Cu(VO)₂(CSN₂H₄)₃Cl(OH)₄]·H₂O, [Cu₂(VO)₂(CSN₂H₄)₂(C₂H₃O₂)₂·(OH)₄], and [Cu₂(VO)₃(CSN₂H₄)₄(C₂H₃O₂)₄(OH)₄] were prepared and characterized in terms of their molecular electrical conductivity, electronic and IR spectra, and thermal behavior. A polymeric structure is proposed in which a thiourea ligand is bonded via a sulfur atom to the tetracoordinated copper(I) and via amino groups to the oxovanadium(IV) ion. The polymeric nature of the complexes is due to bridging via the OH, thiourea, and/or acetate moieties between oxovanadium(IV) coordination centers.     

Thermal behavior of Mannich base N,N′-tetra(4-antipyrylmethyl)-1,2-diaminoethane (TAMEN) and its complexes

The thermal decomposition in air and in nitrogen atmosphere of binuclear complex compounds of Cu(II) and Co(II) containing the Mannich base N,N′-tetra(4-antipyrylmethyl)-1,2 diaminoethane (TAMEN) as a ligand, Cu₂(TAMEN)Cl₄ and Co₂(TAMEN)Cl₄, were investigated. X-ray powder diffractometry, infrared spectroscopy and simultaneous thermogravimetry-differential thermal analysis (TG-DTA), have been used to characterize and to study the thermal behavior of these compounds. The results provided information concerning the stoichiometry, crystallinity, thermal stability and decomposition mechanism of the compounds.     

Thermal behavior of Mannich base N,N′-tetra(4-antipyrylmethyl)-1,2 diaminoethane (TAMEN) and its binuclear complexes

The thermal decomposition of Mannich base N,N′-tetra(4-antipyrylmethyl)-1,2-diaminoethane (TAMEN), and its Ni(II), binuclear complex, Ni₂(TAMEN)Cl₄, in air and in nitrogen atmosphere, were investigated. X-ray powder diffractometry, infrared spectroscopy and simultaneous thermogravimetry-differential thermal analysis (TG-DTA), have been used to characterize and to study the thermal behavior of these compounds. The results provided information concerning the stoichiometry, crystallinity, thermal stability and decomposition mechanism of the compound.     

Mononuclear Cu(II) complexes of novel salicylidene Schiff bases: synthesis and mesogenic properties

Two new Schiff base ligands 1 and 2 (where 1 = 4-(2-hydroxybenzilidenamino)-phenyl-4-(decyloxy)-2-(pent-4-enyloxy)benzoate, 2 = 4-(4-(decyloxy)-2-hydroxybenziliden amino)-phenyl-4-(decyloxy)-2-(pent-4-enyloxy)benzoate) and their copper (Cu)(II) complexes have been synthesised and characterised. The derivatives were fully characterised structurally, and their mesomorphic behaviour was investigated by polarised optical microscopyand differential scanning calorimetry. The structure of Cu(II) complex having 1 as ligand (3) was determined by X-ray diffraction. The Schiff base ligands exhibit enantiotropic nematic phases, the Cu(II) complex 4 shows monotropic nematic phase behaviour, while compound 3 does not show mesomorphism.     

The effect of hydration/dehydration on the AC electrical conductivity of H4PVMo11O40 and some of its cesium salts used as catalysts

Changes in AC electrical conductance G of vanadium substituted 12-molybdophosphoric acid and of its (mono)-acid and neutral cesium salts were studied. Depending on the environment, the electrical conductivity is a combination of protonic and electronic conduction, the protonic one dominating at low temperature.     

Thermal behavior of the polyoxometalates derived from H3PMo12O40 and H4PVMo11O40

The aim of this study is to investigate the influence of some monovalent counter-ions (NH₄ ⁺, K⁺ and Cs⁺) on thermal behavior of polyoxometalates derived from H₃PMo₁₂O₄₀ (HPM) and H₄PVMo₁₁O₄₀ (HPVM) by replacing the protons. The IR and UV-VIS-DRS spectra of some acid and neutral NH₄ ⁺, K⁺, Cs⁺ salts, which derived from HPM and HPVM, confirmed the preservation of Keggin units (KU) structure. The X-ray diffraction spectra clearly showed the presence of a cubic structure. The non-isothermal decomposition of studied polyoxometalates proceeds by a series of processes: the loss of crystallization water; the loss of O₂ accompanying with a reduction of V⁵⁺→V⁴⁺ and Mo⁶⁺→Mo⁵⁺; the loss of constitution water started at 360°C for HPVM salts and 420°C for HPM salts; the decomposition of ammonium ion over 420°C with NH₃, N² and H₂O elimination and simultaneous processes of reduction (V⁵⁺→ V⁴⁺ and Mo⁶⁺→ Mo⁵⁺ or Mo⁴⁺) associating with endothermic effects; reoxidation of Mo⁵⁺, Mo⁴⁺ and V⁴⁺with a strong exothermic effect; destruction of KU to the oxides: P₂O₅, MoO₃ and V₂O₅ and the crystallization of MoO₃. This revised version was published online in July 2006 with corrections to the Cover Date.