SYNTHESIS, CHARACTERIZATION AND THERMAL BEHAVIOUR OF SOLID-STATE COMPOUNDS OF HEAVY TRIVALENT LANTHANIDE AND YTTRIUM MANDELATES

Characterization, thermal stability and thermal decomposition of heavy trivalent lanthanide mandelates Ln(C 6 H 5 CH(OH)CO 2 ) 3 ·2H 2 O (Ln = Tb to Lu and Y) were investigated employing simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), experimental and theoretical infrared spectroscopy, X-ray diffractometry, complexometry and TG-DSC coupled to FTIR. The dehydration of the compounds occurs in a single step and the thermal decomposition of the anhydrous ones occurs in two, three, four or five consecutive steps, with formation of the respective oxides Tb 4 O 7 and Ln 2 O 3 (Ln = Dy to Lu and Y) as final residues. The results also provided 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 heavy lanthanides. Theoretical 3D structure of Y(L)3•2H2O: (a), (c) and (d) isomers (less stable); (b) yttrium(III) mandelate coordinated by hydroxyl and carboxylate groups (the most stable compound).