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Abstract:The Co(II), Ni(II) and Cu(II) metal ions complexes of Bis (4-amino-5-mercapto-1,2,4-triazol-3-yl) alkanes (BATs) have been prepared and characterized by elemental analysis, conductivity measurements infrared, magnetic susceptibility, the electronic spectral data and thermal studies. Based on spectral and magnetic results, the ligands are tetradentate coordinating through the N and S-atoms of BATs; six-coordinated octahedral or distorted octahedral and some times four-coordinated square planar were proposed for these complexes. Activation energies computed for the thermal decomposition steps were compared. The ligands and their metal complexes were tested in vitro for their biological effects. Their activities against two gram-positive, two gram-negative bacteria and two fungal species were found to vary from moderate to very strong.

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IntroductionThe well-established thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques have been reliably widely used over many decades in studying the thermal behaviour and properties of various types of materials and evaluating the thermal parameters for their degradation processes. These methods have allowed determination of the chemical steps of the investigated degradation and the evaluation, by some methods [1,2], of the kinetic parameters for each step. The evaluation of the kinetic parameters has been often performed by using a single thermogravimetric curve (TG curve) recorded at a certain heating rate and atmospheres (under nitrogen or air flow).Some recent results concerning the thermal and thermo-oxidative degradation of polymers or polymeric material, metal complexes, medicinal plant leaves and thermoplastic starch obtained by thermoanalytical methods (TG, DTG, DTA, DSC) have been reported [3 -14]. These reports show that the kinetic parameters evaluated for each step of degradation processes are carried out by using the integral methods considering a reaction order model for the kinetic analysis of the a single thermogravimetric curve data.In our previous studies published elsewhere [15], the temperature variation of the DC electrical conductivity was measured in the range 298 -498 K for the polymer-metal complexes under investigation in the present work, and as a result the activation energies for different temperature segments were worked out. For the reason that a change in the composition may lead to changes of the measured electrical quantities (i.e. the role of adsorbed water), the thermal analysis results (TGA curves) were used only to monitor the loss of adsorbed water in order to study its effect on the DC electrical conductivity at 298 -498 K range. Abstract:The thermal decomposition behavior of the Fe(II), Co(II), Ni(II) and Zn(II) complexes of polydithiooxamide has been investigated by thermogravimetric analysis (TGA) at a heating rate of 20°C min -1 under nitrogen. The Coats-Redfern integral method is used to evaluate the kinetic parameters for the successive steps in the decomposition sequence observed in the TGA curves. The processes of thermal decomposition taking place in the four complexes are studied comparatively as the TGA curves indicate the difference in the thermal decomposition behavior of these complexes. The thermal stabilities of these complexes are discussed in terms of repulsion among electron pairs in the valence shell of the central ion and electronegativity effects.

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