Crystal structures, luminescent and thermal properties of lanthanide complexes with 3,4-dimethylbenzoic acid and 2,2′-bipyridine

Two lanthanide complexes [La(3,4-DMBA)3]n (1) and [Tb(3,4-DMBA)3(DIPY)2]2 (2) (where 3,4-DMBA = 3,4-dimethylbenzoate, DIPY = 2,2′-bipyridine) have been synthesized and then characterized. The single crystals of complexes 1 and 2 were obtained. Complex 1 adopts a distorted monocapped square antiprismatic molecular geometry, while complex 2 forms a distorted square antiprism. Complex 1 is stitched together by edge sharing through carboxylate ligands to form 1D chains along the b axis. The structure of complex 2 consists of 1D chains along the c axis by two kinds of π···π stacking interactions. Two complexes were characterized by elemental analysis, powder X-ray diffraction and IR spectra. The complex 2 shows typical green luminescence in the solid state. Thermal decomposition mechanisms of complexes were discussed by TG–DTG techniques. In the temperature range from 257.15 to 413.15 K, the molar heat capacities of the complexes were measured by DSC. The smoothed heat capacities and thermodynamic functions of complexes were calculated on the basis of fitted polynomial and thermodynamic equations.