Preparation and spectroscopic, and thermal decomposition kinetic studies of europium(III) complex [Eu(HNBD)3] (HNBD: 1-(6-hydroxy-1-naphthyl)-1,3-butanedione)

The complex of Eu(III) with 1-(6-hydroxy-1-naphthyl)-1,3-butanedione (HNBD) was prepared for the first time and characterized by elemental analysis, IR, UV, fluorescence spectrum, and DTA-TG-DTG techniques. The IR and UV-visible spectra showed that Eu(III) ion was coordinated to the HNBD ligand. The fluorescence spectrum showed the presence of Eu3+ characteristic emission. The TG-DTA-DTG curves showed that the thermal decomposition of the anhydrous complex was a two-stage process and the final residue was Eu2O3. The thermal decomposition kinetic parameters of the complex were evaluated from TG-DTG data by using three kinds of integral methods (Coat-Redfern equation, Horowitz and Metzger equation, Madhusudanan-Krishnan-Ninan equation). The kinetic parameters of the first stage are E* = 164.02 kJ·mol−1, A = 1.31 × 1015 s−1, ΔS* = 42.27 J·K−1·mol−1, ΔH* = 159.51 kJ·mol−1, ΔG* = 136.54 kJ·mol−1, and n = 3.1, those of the second stage are E* = 128.52 kJ·mol−1, A = 1.44 × 106 s−1, ΔS* = - 136.89 J·K−1·mol−1, ΔH* = 120.41 kJ·mol−1, ΔG* = 283.85 kJ·mol−1, and n = 1.1.