Studies on thermal decomposition of uranium(VI) and thorium(IV) complexes of o-carboxy N,N′-dimethylbenzylamine by thermoanalytical techniques in static air atmosphere

Abstract

Summary The o-carboxy N-N′-dimethylbenzylamine uranium(VI) and thorium(IV) complexes, o-C6H4COOHCH2N-(CH3)2UO2SO4 (I), o-C6H4COOHCH2N(CH3)2UO2(NO3)2 (II), o-C6H4COOHCH2N(CH3)2UO2Cl2 (III), and o-C6H4CO-OHCH2N(CH3)2Th(NO3)4 (IV) were prepared and studied by means of thermoanalytical techniques in static air atmosphere to understand their mode of decomposition and thermal stability. Their compositions were investigated by elemental analysis in order to ensure their purity, and structure elucidations were based on proton NMR and IR spectra. Study of their thermal decomposition showed that they pyrolyzed in stages: the degradation of square bipyramidal complexes (I and III) occurred in four stages; hexagonal bipyramidal complex (II) also followed the same pattern. The decomposition of bicapped square antiprism complex (IV) proceeded in three steps. The thermal decomposition of these complexes occurred with the loss of inorganic and organic fragments and exhibited almost the same mode of decomposition. The composition of the intermediate formed during degradation was confirmed by microanalysis and IR spectroscopy. The residue after heating above 480 °C corresponded to metal oxide. It follows from the results that the thermal stability of the complexes increases in the following sequence: Complex II, Complex IV < Complex III < Complex I