Journal of Thermal Analysis and Calorimetry, Vol. 63 (2001) 105–116 THERMAL STUDIES ON SOLID COMPLEXES OF URACIL WITH SOME DIVALENT TRANSITION METAL IONS H. Ölmez, O. Z. Yeºilel and H. Içbudak * Department of Chemistry, Faculty of Arts and Sciences, Ondokuz Mayis University, 55139 Kurupelit, Samsun, Turkey (Received September 3, 1999; in revised form August 25, 2000) Abstract The thermal behaviour of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pd(II) complexes of uracil was studied by TG, DTG and DTA in a dynamic nitrogen atmosphere. Two processes occur in the isolated uracil complexes: dehydration and pyrolytic decomposition. In the hydrated com- plexes, the first stage observed was the loss of water molecules, which was followed by decomposi- tion of the uracil. The thermal dehydration of the complexes occurred in from one to three steps. The final decomposition products were found to be the respective metal oxides, except in the cases of the Co(II) and Pd(II) complexes, which produced metallic cobalt and palladium, respectively. The order of reaction and energy of activation for the dehydration stage were evaluated. Keywords: divalent transition metals, kinetic analysis, thermal analysis, uracil complexes Introduction Various studies on the interactions of metal ions with nucleic acids have been re- ported in recent years [1–5]. The metal complexes of purines, pyrimidines and their nucleotides play a dominant role in many biochemical systems. However, the study of such large biological systems is very complex. This is due to the presence of a plethora of potential metal-binding sites in the nucleic acids and their constituents. Therefore, to promote an understanding of these important systems, wide-ranging studies on metal complexes with isolated nucleobases have been performed [7–12]. Some of the metal complexes of nucleic acids and their constituents are well known, which is very important because of the biological and clinical implications of these compounds [13]. The complexes of Co(III) and Cr(III) with nucleotides and their de- rivatives are useful for determining the points where enzymes are activated or inhib- ited [14]. The platinum group metal complexes with purines, pyrimidines and nucleic 1418–2874/2001/ $ 5.00 © 2001 Akadémiai Kiadó, Budapest Akadémiai Kiadó, Budapest Kluwer Academic Publishers, Dordrecht * Author for correspondence: E-mail: icbudak@omu.edu.tr