Crystal structures and thermal decomposition kinetics of lanthanide complexes with 3,4,5-trimethoxybenzoic acid and 1,10-phenanthroline

A series of lanthanide complexes with the 3,4,5-trimethoxybenzoic acid (3,4,5-tmoba) and 1,10-phenanthroline(phen), [Ln(3,4,5-tmoba)₃phen]₂(Ln = Pr(1), Nd (2) and Ho(3)), have been synthesized and characterized by a series of techniques including elemental analysis, IR spectra, X-ray crystallography and TG/DSC-FTIR technology. The three complexes have two kinds of coordination modes, in which the Pr³⁺ and Nd³⁺ cations are nine-coordinated and the Ho³⁺ cation is eight-coordinated. The three-dimensional IR accumulation spectra of gaseous products for complexes 1?C3 were analyzed and the gaseous products were identified by the typical IR spectra obtained from the 3D surface graphs. Meanwhile, we obtained the activation energy E of the first steps of complexes 1?C3 by the integral isoconversional non-linear (NL-INT) method and discussed the non-isothermal kinetics of complexes 1?C3 using the Malek method. Finally, SB(m, n) was defined as the kinetic method of the first-step thermal decomposition. The thermodynamic parameters ??G ^??, ??H ^?? and ??S ^?? of activation at the peak temperature were also calculated.