Thermal properties of some pyrimidine, purine, amino-acid and mixed ligand complexes

Mn(II), Fe(III), Co(II), Ni(II), Zn(II) and Cd(II) complexes of barbital, thiouracil, adenine, amino acids, beside mixed metals and mixed ligands were prepared. The structures of the complexes are of Oh, distorted Oh, Td and distorted Td geometries. Differential thermal (DTA) and thermogravimetric analysis (TG) of the complexes pointed to their stability. The change of entropy values, ΔS#, showed that the transition states are more ordered than the reacting complexes. The fractions appeared in the calculated order of the thermal reactions, n, confirmed that the thermal reactions proceed in complicated mechanisms where the bond between the central metal ion and the ligands dissociates after losing small molecules such as H2O. In most cases, the free radical species of the ligands are assigned to exist through decomposition mechanisms.

► Synthesis of novel complexes from barbital, thiouracil, adenine, amino acids.
► We examine their thermal stability using DTA and TG techniques.
► The thermodynamic parameters of the decomposition reaction were evaluated.
► We proposed mechanisms for the decomposition processes.