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

Abstract

A series of lanthanide coordination polymers with a novel flexible hexapodal ligand, formulated as [Ln 2 (TTHA)(H 2 O) 4 ]·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)(H 2 O) 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 (CO 2 ) 4 units with two different shapes of three-dimensional channels determining certain adsorption for H 2 and CH 4 . The thermogravimetric analyses and XRD data show that the guest water molecules and a coordinated water molecule with each metal center are thermally unstable, but the orders of the framework structures of complexes 1 − 4 are thermally stable to 400 °C. Complex 5 shows a 2D network with 1D inorganic chains bridged by the ligands, and the 3D network was extended through π···π 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 nm, respectively, and may be good candidates for light-emitting diodes (LEDs) and light applications.