Abstract
Divalent metal complexes of ligand 2-methoxybenzylidenepyruvate with Fe, Co, Ni, Cu and Zn as well as sodium salt were synthesized and investigated in the solid state. TG curves of these compounds were obtained with masses sample of 1 and 5mg under nitrogen atmosphere. Different heating rates were used to characterize and study these compounds from the kinetic point of view. The activation energy and pre-exponential factor were obtained applying the Wall-Flynn-Ozawa method to the TG curves. The obtained data were evaluated and the values of activation energy (Ea / kJ mol-1) was plotted in function of the conversion degree (α). The results show that due to mass sample, different activation energies were obtained. The results are discussed mainly taking into account the linear dependence between the activation energy and the pre exponential factor, where was verified the effect of kinetic compensation (KCE) and possible linear relations between the dehydrations steps of these compounds.
Highlights
These were characterized by simultaneous TG-differential thermal analysis (DTA) and differential scanning calorimetry (DSC) curves, infrared spectroscopy and X-ray diffractometry [2]
This compounds are in agreement with the stoichiometry M:L2 nH2O where M represents the bivalent metal ions, L is the ligand and n is the number of water molecules
The kinetic parameters of dehydration of these compounds were evaluated from the TG curves shown in the Figures 1 and 2
Summary
Resumo: o sal de sódio de 2-metoxibenzalpiruvato assim como os complexos metálicos do ligante 2-metoxibenzalpiruvico com os íons Fe, Co, Ni, Cu e Zn foram preparados e analisados no estado sólido. Curvas termogravimétricas (TG) destes compostos foram obtidas com massa de amostra em torno de 1 e 5mg em atmosfera de nitrogênio. A energia de ativação e o fator pré-exponencial foram obtidos com a aplicação, nas curvas TG, do método proposto por Wall-Flynn-Ozawa. Os resultados apresentaram que devido a massa de amostras, diferentes energias de ativação foram obtidos. Os resultados também foram discutidos tendo em vista a dependência entre a energia de ativação e o fator pré-exponencial, onde foi verificado o efeito de compensação cinética (KCE) e possível relação linear entre as etapas de desidratação destes compostos.
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