Synthesis, crystal structures and thermal decomposition kinetics of four new lanthanide complexes with 3,4-dimethylbenzoic acid and 1,10-phenanthroline

A new series of lanthanide complexes [Ln(3,4-DMBA)3phen]2 [Ln(III) = Nd(1), Sm(2), Tb(3) and Dy(4), 3,4-DMBA = 3,4-dimethylbenzoate, phen = 1,10-phenanthroline] have been synthesized and characterized by elemental analysis, infrared spectra and TG-DTG techniques. The single crystals of the complexes 3 and 4 have been obtained and their structures have been determined by single-crystal X-ray diffraction. In the complexes 3 and 4, each Ln(III) ion is coordinated by four bidentate-bridging 3,4-DMBA ligands, one bidentate-chelating 3,4-DMBA group and one bidentate-chelating phen ligand, giving a coordination number of eight. The complex 3 shows bright green luminescence under ultraviolet light in the solid state. Thermal analysis of the complexes 1–4 are discussed by TG-DTG and IR techniques. The non-isothermal kinetics of the complexes 1–4 are investigated by using double equal-double step method. The thermodynamic parameters (ΔH≠, ΔG≠ and ΔS≠) and kinetic parameters (activation energy E and the pre-exponential factor A) of the four complexes are also calculated.