gamma-Zirconium and gamma-titanium phosphates containing organic diamine 2,9-dimethyl-1,10-phenanthroline and its in situ formed copper complex were studied by thermal analysis and physical measurements. All the derived materials show a layered structure and their interlayer distance is increased with respect to that of their precursors. Melting, simultaneous vaporization and oxidation, as well as a decomposition process take place in the pure diamine. After dehydration, all the intercalation materials undergo a two-step decomposition. The presence of the formed copper complex between the layers of the two ion-exchangers considered shows a destabilizing effect with respect to the intercalated diamine materials, resulting in a decrease of the decomposition temperatures and the activation energy of decomposition. The application of the isoconversional Ozawa-Flynn-Wall method substantially confirms the obtained results. (c) 2006 Elsevier B.V. All rights reserved.