Thermal properties of some Co~Ⅱ, Ni~Ⅱ and Cu~Ⅱ complexes of new substituted pyrimidine compounds

摘要

Twenty complexes derived from 6-amino-2-thiouracil (H_2ATU), 5-aminouracil (H_2AUH) and some of their arylazo derivatives with Co~Ⅱ, Ni~Ⅱ and Cu~Ⅱ have been prepared and analyzed in the mole ratios 1:1,1:2, 2:1, 2:3 and 3:1 (M:L). The thermal analysis of the complexes was studied by TGA and DTA techniques to give more information on the structure of the investigated materials. The thermodynamic parameters of the decomposition reaction were evaluated and discussed. The change of entropy values, ΔS~#, showed that the transition states are more ordered than the reacting complexes. The thermal processes proceed in complicated mechanisms where the bond between the central metal ion and the ligand dissociates after losing of small molecules such as H_2O, CO_2 or NH_3. The decomposition is usually ended by the formation of metal oxide which could be contaminated with metal sulphate in case of complexes derived from H_2ATU or its azo derivatives.