Self-Assembly of 1D, 2D, and 3D Lanthanide-Metal Coordination Polymers Based on a 2-(Pyridin-4-yl)-4,5-imidazoledicarboxylate Linker: Synthesis, Structures, and Luminescence

Three series of novel lanthanide-based 1D, 2D, and 3D metallic coordination frameworks involving the 2-pyridin-4-yl-4,5-imidazoledicarboxylic acid (H3PIDC) ligand have been characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction. The compound [Tb(PIDC)(H2O)4]center dot H3PIDC center dot 4H2O (1) upon slow evaporation at room temperature gave a 1D coordination chain framework constructed of [Tb2O2] dimers bridged through the carboxylate groups of PIDC3 ligands; a 3D supramolecular structure is generated through hydrogen bonding and pp interactions. The second kind of lanthanide-based coordination framework, namely [Ln(H2PIDC)(ox)H2O]center dot 3H2O [Ln = Sm (2), Gd (3), Dy (4), and Ho (5), ox = oxalic acid], synthesized under hydrothermal conditions, self-assemble through Ln2[H2PIDC]2 building blocks and bridging oxalate ligands to give a 2D coordination layer structure. The adjacent layers stack to form a 3D supramolecular framework through weak interactions such as hydrogen bonding and pp interactions. The third series of lanthanide-based coordination compounds with chemical formula [Ln(HPIDC)(ox)1/2H2O]center dot 3H2O [Ln = Gd (6), Dy (7), Tb (8) and Ho (9)] were also synthesized by hydrothermal reaction. These isostructural compounds contain an infinite LnOCOLn zigzag chain, which connect to each other through the oxygen atoms of the HPIDC2 ligands to form a wave-like layer. The layers are bridged by oxalate ligands to generate a 3D coordination framework.