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(H2O)2]·H2O (Lndouble bond; length as m-dashPr(1), Nd(2), Eu(3), Gd(4), Tb(5), Er(6); H2PYDCdouble bond; length as m-dash3,4-pyridinedicarboxylic acid) have been successfully synthesized and characterized. Their isostructures are built up from one-dimensional (1D) infinite chains cross-linked via the tri-connected PYDC ligands, leading to the two-dimensional (2D) layer structure. The adjacent layers are further extended into three-dimensional (3D) supramolecular frameworks through hydrogen bonding and π–π 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.