Synthesis, thermal properties and spectroscopic study of solid mandelate of light trivalent lanthanides

Characterization, thermal stability and thermal decomposition of light trivalent lanthanide mandelates Ln(C6H5CH(OH)CO2)3·nH2O (Ln = La to Gd, except Pm) were investigated employing simultaneous thermogravimetry and differential thermal analysis (TG–DTA), differential scanning calorimetry (DSC), experimental and theoretical infrared spectroscopy, elemental analysis, X-ray diffractometry, complexometry and TG–DSC coupled to FTIR. The dehydration of the lanthanum, samarium, europium and gadolinium compounds occurs in a single step while for praseodymium and neodymium ones it occurs in two consecutive steps. The thermal decomposition of the anhydrous compounds occurs in three, four or five consecutive steps, with formation of the respective oxides CeO2, Pr6O11 and Ln2O3 (Ln = La, Nd to Gd) as final residues. The results also provide information concerning the composition, thermal behavior and gaseous products evolved during the thermal decomposition of these compounds. The theoretical and experimental spectroscopic data suggest the possible modes of coordination of the ligand with the lanthanum.

► From TG curves and complexometry results the general formula could be established.
► The thermal stability and thermal decomposition were established from TG-DTA curves.
► The dehydration enthalpies were calculated from DSC curves.
► The gaseous products evolved during the thermal decomposition were monitored by FTIR.