Thermal properties of some biologically active 5-(p-substituted phenylazo)-6-aminouracil complexes

Nine complexes derived from substituted phenylazo-6-aminouracil (-H, p-OCH3 and p-CH3) with CoII, NiII and CuII have been prepared and analyzed in the mole ratios 1:3, 1:2 and 2:3 (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 H2O, C2H5OH or HCl. The decomposition is usually ended by the formation of metal oxide.