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Thermal stability, thermokinetic, and decomposition mechanism of copper(II) triazole-3-thiones complexes

S.A.Ibrahim, S.A.El-Gyar, A.Abd El-Sameh*, M.A.El-Gahami

The thermal decomposition study of copper(II) complexes [a series of copper(II) complexeswith 4-amino-5-benzyl-4H-1,2,4-triazole-3-thione (ABT), 5-benzyl-4-(benzylideneamino)-4H-1,2,4-triazole-3-thione(BBT), 5-benzyl-4- [(2-hydroxybenzylidene)amino]-4H-1,2,4-triazole-3-thione (HBHT) and 5- benzyl-4-[(4-mehtoxybenzylidene)amino]-4H-1,2,4-triazole-3-thione (BMT)] was monitored by TG, DTG and DTA analysis in dynamic atmosphere of nitrogen. TG, DTG and DTAstudies confirmed the chemical formulations of these complexes and showed that their thermal degradation take place in two to four steps depending on the type of ligand present. The kinetic parameterswere determined fromthe thermal decomposition data using the graphical methods of Coats-Redfern and Horowitz-Metzger. Thermodynamic parameters were calculated using standard relations. Negative values of the entropy indicate a more ordered activated state thatmay be possible through the chemisorption of oxygen and other decomposition products. In most cases the values of the activation energy for the second decomposition stage were found to be higher than that of the first stage, this may be attributed to the structural rigidity of the ligands. The decomposition stability order of the complexes depends on the structural feature of ligand, copper(II) complex containing the ABT ligand being the most stable one. The activation energies of the thermal degradation steps lie in the range 9.83-70.86 kJmol-1.