Controlled syntheses, structures and photoluminescence of two europium coordination polymers based on 2,4-dcp (2,4-dichlorophenoxyacetate) and 4,4′-bpy (4,4′-bipyridine) ligands

Two new one-dimensional europium coordination polymers, namely {[Eu(2,4-dcp)3(H2O)2]·(4,4′-bpy)(H2O)}n (1) and {[Eu(2,4-dcp)3(H2O)2]·(4,4′-bpy)1.5(H2O)2}n (2) were hydrothermally synthesized by controlling the pH of the reaction solution, and were characterized by elemental analysis, IR, TGA, powder X-ray diffraction and single crystal X-ray diffraction. Single-crystal X-ray diffraction studies indicate that the two europium coordination polymers adopt analogous linear chain structures with a {Eu2(2,4-dcp)5(H2O)4}, and a {Eu2(2,4-dcp)6(H2O)4} dimeric repeat units for 1 and 2, respectively. The europium centers of 1 and 2 are also bound to two water molecules resulting in nine-coordinate, distorted tricapped trigonal-prism and monocapped square antiprism geometries, respectively. The pyridine nitrogen atoms of the 4,4′-bpy ligands do not coordinate to the metal centers in complexes 1–2; instead, they direct the formation of 2D sheet networks via hydrogen bonding interactions. Both 1 and 2 emit the intense red characteristic luminescence of Eu3+ ion at room temperature, with long lifetimes of up to 0.8879 and 0.7571 ms, respectively.