Synthesis, Characterization and Thermal Decomposition of Samarium Complexes

摘要

This work deals with the synthesis, characterization and kinetics of the thermal decomposition of complexes of general formula: Ln(β-dik)_3L (where Ln = Sm~(+3), β-dik= 4,4,4-trifluoro-1-phenyl-1,3-butanedione (btfa) and L = 1,10-fenantriline (phen) or 2,2-bipiridine (bipy). The complexes in the power form were synthesized from the direct reaction of SmCl_3 with β-diketone and the ligands. The synthesized complexes presented a weak red luminescence. The powders were characterized by melting point, FTIR spectroscopy, UV-visible absorption spectrophotometry, elemental analysis, scanning differential calorimeter (DSC) and thermogravimetry (TG). The kinetic parameters were obtained from the thermogravimetric data by the non-isothermal integral methods proposed by Coats-Redfern and Madhusudanan, as well as by approximation methods proposed by Horowitz-Metzger and Van Krevelen. The kinetic parameters in the dynamic heating method were determined with the Coats-Redfem equation, using the thermal decomposition model with the data obtained in the isothermal heating experiments. The IR spectra evinced that the metal ion is coordinated to the β-diketone via C=O and is coordinated to the ligand second via C-N groups. The TG/DTG/DSC curves of the complexes show that they decompose before melting. The profiles of the thermal decomposition of the Sm(btfa)_3phen and Sm(btfa)_3bipy showed three and four decomposition stages, respectively. Our data suggests that the thermal stability of the complexes under investigation followed the order: Sm(btfa)_3phen > Sm(btfa)_3bipy, The kinetic models that best described the thermal decomposition reaction for the Sm(btfa)_3bipy was R2, for the Sm(btfa)_3phen was F1.