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New iron-cobalt clusters with silicon-containing dicarboxylic acids

100%
Cazacu M., Vlad A., Turta C., Lisa G.
Open Chemistry
|
2012
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vol. 10
|
issue 4
1079-1086
EN
For the first time, silicon-containing dicarboxylic acids were used to prepare two new heterotrinuclear carboxylates of the composition [Fe2IIICoIIO(Bcpdps)3(H2O)3], I, where H2Bcpdps ≡ HOOC-C6H4-Si(C6H5)2-C6H4COOH, and [Fe2IIICoIIO(Ipds)3(H2O)3], II, where H2Ipds ≡ [HOOC-C6H3(CO)2N-(CH2)3-(CH3)2Si]2O. The precursor for these two complexes was trinuclear µ3-oxo-hexaacetate triaqua diiron(III)cobalt(II) cluster, {Fe 2 CoO}, in which the acetate anions were subsequently substituted by silicon-containing dianions. The resulting products were characterized by elemental analysis, thermogravimetry, Fourier Transform Infrared (FTIR), Energy-Dispersive X-ray Fluorescence (EDXRF), and Mossbauer spectroscopies (MS). The investigation by MS revealed the presence of the iron(3+) ions in high spin state and having the close environment. Thermogravimetric analysis results indicated an improving in the thermal stability by replacing acetate anions with silicon-containing carboxyl ligands. This widens the temperature range in which such compounds can be used in practical applications. [...]
2
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Synthesis and un-isotherm kinetic study of some ferrocene acids

100%
Apreutesei D., Lisa G., Hurduc N., Scutaru D.
Open Chemistry
|
2004
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vol. 2
|
issue 4
553-562
EN
The goal of this paper is to study thermal stability of some ferrocenes with acidic functional groups. Some other kinetic characteristics such as critical temperature and the rate constant corresponding to maximal degradation speed have been also evaluated. The type of functional units adjacent to the ferrocenyl unit determines thermal stability of ferrocene compounds. Groups with a powerful withdrawing effect determine a decreasing of the temperatures at which the material starts to lose weight. If a very long alkyl chain is connected to the ferrocene unit, a shielding effect in respect to the other carboxylic groups was observed, with an increase of the thermal stability.
3
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Physico-chemical properties of Chitosan films

88%
Balau L., Lisa G., Popa M., Tura V., Melnig V.
Open Chemistry
|
2004
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vol. 2
|
issue 4
638-647
EN
Chitosan films obtained by dry phase inversion were prepared from an aqueous solution of chitosan in acetic acid. The films, of thickness less than 20 μm, were transparent, very flexible and had smooth surfaces. Increasing the film thickness induced an increase of the internal tensions and the consequent formation of a rough surface. Structural investigations by X-ray diffraction and Fourier transform IR analysis, showed that the chitosan films, as prepared, are amorphous. Further annealing to evaporate acetic acid and water traces, changed the amorphous phase into a more ordered phase, characterized by diffraction peaks at 2θ values of 9, 17, 20 and 23 degrees. Thermal investigations by TG, DTG, and DTA revealed that the decomposition of the chitosan films as prepared proceeds in two stages, starting from 180°C and 540°C.
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