Thermal decomposition of some copper-iron polynuclear coordination compounds containing glycine as ligand, precursors of copper ferrite

The thermal behaviour of three coordination compounds, precursors of copper ferrite, namely [Fe2Cu(NH2CH2COOH)4.5](NO3)8.4H2O (I), [Fe2Cu(NH2CH2COO)4(OH)3](NO3).H2O (II) and [Fe2Cu(NH2CH2COO)6(NH2CH2COOH)2](NO3)2 (III), has been investigated. For a complete and reliable assignment of the thermal transformations, the isolable intermediates and end products were characterized by IR and X-ray diffraction. The coordination compounds which undergo a stepwise decomposition in the temperature range 60-375 deg.. C are less stable than free glycine (206-375 deg.. C), indicating the occurrence of some self-propagating reactions. The nitrate/glycine ratio contained by the parent coordination compound, affects the final decomposition temperature (decreases as the ratio increases) but not the decomposition mechanism, and the mean particles size of the decomposition end product Fe2CuO4 (an optimum value has to be found in order to avoid local combustion occurrences)