THERMAL-DEGRADATION AND CRYSTALLOGRAPHIC DATA OF METAL-COMPLEXES OF OXOPURINES AND THIOPURINES

The thermal behaviour of metal compounds of the naturally occurring ox opurines hypoxanthine, xanthine and uric acid and of the synthetic pyr azolopyrimidines allopurinol and alloxanthine as well as of the thiopu rine 6-mercaptopurine has been investigated using thermogravimetric an d X-ray crystallographic techniques. The thermogravimetric data confir m the structural characteristics of the metal complexes. The degradati on of hydrated complexes occurs in two steps with a dehydration reacti on followed by complete decomposition to the corresponding metal oxide s. Anhydrous compounds are decomposed in one step overall reactions. T he temperature range of dehydrations of the hydrated complexes strongl y depends on the binding mode of the water molecules. The reaction rat e of the final decompositions of these complexes seems to be influence d by the respective metal ions. Copper and iron complexes show a sharp increase in the reaction rate in respect of the complexes of cobalt a nd nickel, whereas zinc, cadmium and manganese compounds are slowly de composed over a wide temperature, range.