Syntheses, structures and photoluminescence of a series of lanthanide-organic frameworks involving in situ ligand formation

A series of lanthanide-organic frameworks with aromatic pyridinecarboxylate ligand, generally formulated as [Ln(PYDC)(C2O4)(0.5)(H2O2]center dot H2O (Ln Pr(1), Nd(2), Eu(3), Gd(4), Tb(5), Er(6): H2PYDC 3,4-pyridinedicarboxylic acid) have been successfully synthesized and characterized. Their isostructures are built Up from one-dimensional (I D) infinite chains cross-linked via the tri-connected PYDC ligands, leading to the two-dimensional (21)) layer structure. The adjacent layers are further extended into three-dimensional (31)) supramolecular frameworks through hydrogen bonding and R-7t pi-pi stacking interactions. Interestingly, the oxalate bridging ligand is believed to form via in situ ligand synthesis through decarboxylation of the organic precursor, H2PYDC. Complexes 3 and 5 exhibit strong fluorescent emissions in the visible region at room temperature. (C) 2008 Elsevier Inc. All rights reserved.