Study of isothermal decomposition of lanthanide mixed complexes with 2,2,6,6-tetramethyl-3,5-heptanodione and 1,10-phenanthroline

Isothermal decomposition kinetic of three lanthanide mixed complexes with the general formula of Ln(thd)3phen (where Ln=Nd³⁺, Sm³⁺ or Er³⁺, thd=2,2,6,6-tetramethyl-3,5-heptanodione and phen=1,10-phenanthroline) has been studied in this work. The powders were characterized by their melting point, elemental analysis, FTIR spectroscopy and thermogravimetry. The isothermal TG curves have been recorded under the same conditions at 265–285, 265–285 and 250–270°C for Nd(thd)₃phen, Sm(thd)₃phen and Er(thd)₃phen, respectively. The kinetic parameters, i.e. activation energy, reaction order and frequency factor were obtained through the technique of lineal regression using the relation g(α)=kt+g ₀. The analysis was done at decomposed fractions between 0.10–0.90. The values of activation energy were: 114.10, 114.24 and 115.04 kJ mol^–1 for the Nd(thd)₃phen, Sm(thd)₃phen and Er(thd)₃phen complexes, respectively. The kinetic models that best described the isothermal decomposition reaction the complexes were R1 and R2. The values of activation energy suggests the following decreasing order of stability: Nd(thd)₃phen<Sm(thd)₃phen<Er(thd)₃phen.