Synthesis, characterization and thermochemical properties of four new lanthanide complexes with 3,5-diisopropylsalicylic acid and 1,10-phenanthroline

Four lanthanide complexes with a general formula [Ln(3,5-Dipr-2-OHBA)3(phen)]2 (Ln = La(1), Nd(2), Eu(3) and Tb(4); 3,5-Dipr-2-OHBA = 3,5-diisopropylsalicylate; phen = 1,10-phenanthroline) were synthesized and characterized by elemental analysis, infrared spectra (IR), powder X-ray diffraction (XRD) and thermogravimetry, differential scanning calorimetry techniques with Fourier transform infrared (TG/DSC–FTIR) technology. The luminescent properties of the complexes 3 and 4 were studied. The thermal decomposition processes of the title compounds were studied using the TG/DSC–FTIR coupling techniques. Heat capacities of the complexes were measured by DSC. And the values of the experimental heat capacities were fitted to a polynomial equation with the least-squares method. Based on the fitted polynomial and thermodynamic equations, the smoothed heat capacities and thermodynamic functions (HT − H298.15 K), (ST − S298.15 K), and (GT − G298.15 K) were calculated.