Novel Structures and Luminescence Properties of Lanthanide Coordination Polymers with a Novel Flexible Polycarboxylate Ligand

A series of lanthanide coordination polymers with a novel flexible hexapodal ligand, formulated as [Ln(2)(TTHA)-(H2O)(4)]center dot 9H(2)O (TTHA = 1,3,5-triazine-2,4,6-triamine hexaacetic acid; Ln = 1, Eu; 2, Tb; 3, Gd; 4, Dy) and [Yb-2(TTHA)-(H2O)(2)] (5) have been hydrothermally synthesized and characterized. Complexes 1-4 possess the same three-dimensional 4-connected 4(2)8(4) networks constructed from Ln(2)(CO2)(4) units with two different shapes of three-dimensional channels determining certain adsorption for H-2 and CH4. The thermogravimetric analyses and XRD data show that the guest water molecules and a coordinated water molecule with cacti metal center are thermally unstable, but the orders of the framework structures of complexes 1-4 are thermally stable to 400 degrees C, Complex 5 shows a 2D network with I D inorganic chains bridged by the ligands, and the 3D network was extended through pi center dot center dot center dot pi stacking interactions between triazine rings. Photoluminescence measurements show that complexes 1 and 2 are highly emissive at room temperature with quantum yields of 31% and 89%, which even amount to unexpectedly 77% and 96% after thermal treatments at 394 and 343 rim, respectively, and may be good candidates for light-emitting diodes (LEDs) and light applications.