Two Novel Binuclear Lanthanide Complexes with 2,5‐Dichlorobenzoic Acid and 5,5’‐Dimethyl‐2,2’‐bipyridine: Crystal Structures, Luminescence and Thermal Properties

Abstract

Two novel binuclear lanthanide complexes [Ln(2, 5-DClBA) 3 (5,5'-DM-2,2'-bipy)(H 2 O)] 2 (5,5'-DM-2,2'-bipy) (Ln = Eu(1), Tb(2)); 2,5-DClBA = 2,5-dichlorobenzoate; 5,5'-DM-2,2'-bipy = 5,5'-dimethyl-2,2'-bipyridine) have been successfully synthesized via conventional solution method and then characterized by singlecrystal X-ray diffraction and elemental analysis. These two binuclear complexes differ from other reported binuclear complexes, because the free neutral ligands are not common in crystal structure. The complexes are isomorphic, which have the same coordination number of eight with a distorted square antiprismatic molecular geometry. The binuclear units feature hydrogen bonding (OÀH···N and CÀH···Cl) and p-p stacking interactions assemble the adjacent molecular units into 1D, 2D and 3D supramolecular novel structures. It is worth noting that the novel 1D supramolecular structure is formed by the hydrogen bonding interaction between the nitrogen atoms of free 5,5'-DM-2,2'-bipy ligand and the oxygen atom of the coordination water molecule. The thermal decomposition mechanism of the two complexes were studied by TG/DSC-FTIR techniques. Additionally, the luminescence spectra and lifetime have been studied in detail. The results indicate that Eu 3 + ion and Tb 3 + ion could be sensitized by ligands and thus emitted intense characteristic red and green luminescence, respectively.