Syntheses, Structures and Luminescent Properties of the Heterometallic Complexes [Ln2Zn2(2,5-pydc)5(H2O)2]•4H2O

The new heterometallic coordination polymers [Ln(2)Zn(2)(2,5-pydc)(5)(H2O)(2)]center dot 4H(2)O (Ln=Sm (1) and Ln=Eu (2); 2,5-pydc: 2,5-pyridinedicarboxylic acid) were synthesized from the reaction of Ln(2)O(3) and Zn(CH3COO)(2)center dot 2H(2)O with corresponding ligands under hydrothermal conditions. The complexes were characterized by elemental analysis, IR spectroscopy, powder X-ray diffraction (XRD) and single crystal X-ray diffraction. Structural analyses reveals that complexes 1 and 2 are isomorphous and crystallize in the monoclinic space group P2(1)/c. In complexes 1 and 2, there are two kinds of coordination modes for the 2,5-pyridinedicarboxylic acid ligand. Ln and Zn are connected to form a two dimensional (2D) layer structure by coordination mode I of 2,5-pyridinedicarboxylic acid and the layers further link to each other to form an intricate three dimensional (3D) network by coordination mode II. In addition, the luminescent properties and thermogravimetric (TG) analyses of the title complexes were analyzed in detail. The luminescence of Sm and Eu in these complexes was greatly improved because of the introduction of Zn.