Synthesis, crystal structure, luminescent property and antibacterial activity of lanthanide ternary complexes with 2,4,6-tri(2-pyridyl)-s-triazine

Several ternary complexes of rare earth ions (RE3+ = Sm3+, Eu3+, Tb3+, Dy3+) with benzoic acid and a neutral ligand 2,4,6-tri(2-pyridyl)-s-triazine (TPTZ) have been synthesized. The crystal structure of the [Eu(C6H5COO)3(TPTZ)(H2O)]2·2C2H5OH·1.25H2O complex was determined by single-crystal X-ray diffraction and it is characteristic of triclinic with P−1 space group. Especially, the crystal has two types of coordination environment. One is mononuclear and the other is dinuclear. Each europium ion is nine-coordinately bonded to three nitrogen atoms of TPTZ, five oxygen atoms of three benzoic ions and one oxygen atom of water molecule. Furthermore, there exist three coordinate forms between C6H5COO− and Eu3+ ions in the crystal. One is chelating bidentate (two oxygen atoms), another is bridge coordinating (two oxygen atoms) and the other is monodentate (one oxygen atom). The compositions of these ternary complexes were characterized by elemental analysis, rare earth coordination titration, molar conductivity measurement, 1H NMR spectroscopy, IR spectroscopy and UV–vis absorption spectroscopy. The luminescence spectra and luminescence decay time were then studied. The luminescence intensities of the ternary complexes may result from the antenna effect of TPTZ and benzoic acid ligands as well as the reduce of solvent-quenching effect. Moreover, these ternary complexes exhibited superior antibacterial activity against Escherichia coli.