Thermal behaviour of malonic acid, sodium malonate and its compounds with some bivalent transition metal ions

Characterization, thermal stability and thermal decomposition of transition metal malonates, MCH 2C 2O 4· nH 2O (M = Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II)), as well as, the thermal behaviour of malonic acid (C 3H 4O 4) and its sodium salt (Na 2CH 2C 2O 4·H 2O) were investigated employing simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), infrared spectroscopy, TG-FTIR system, elemental analysis and complexometry. The dehydration, as well as, the thermal decomposition of the anhydrous compounds occurs in a single step. For the sodium malonate the final residue up to 700 °C is sodium carbonate, while the transition metal malonates the final residue up to 335 °C (Mn), 400 °C (Fe), 340 °C (Co), 350 °C (Ni), 520 °C (Cu) and 450 °C (Zn) is Mn 3O 4, Fe 2O 3, Co 3O 4, NiO, CuO and ZnO, respectively. The results also provided information concerning the ligand's denticity, thermal behaviour and identification of some gaseous products evolved during the thermal decomposition of these compounds.