Lanthanide-Organic Frameworks (LnOFs) Containing 1D Metal/Oxygen Ribbons with Cubane-like and Triangle Motifs: Synthesis, Structure, Luminescence and Slow Magnetic Relaxation

Four lanthanide-based three-dimensional(3D) complexes {[Ln5(μ2-O)(μ3-OH)5(TCA)2(NO3)(CH3COO)(H2O)2]⋅NH(CH3)2⋅DMA⋅(H2O)3}n (H3TCA=4,4′,4′′-tricarboxytriphenylamine; DMA=N,N-dimethylacetamide; Ln=Dy(1), Y(2)) and {[Ln2(μ2-OH)(μ3-OH)2(TCA)(H2O)]⋅DMA⋅H2O}n (Ln=Er(3), Yb(4)) have been hydrothermally synthesized based on a flexible tricarboxylate ligand H3TCA. Single-crystal X-ray diffraction studies reveal that complexes 1–4 exhibit a 3D framework constructed through well-isolated one-dimensional(1D) metal/oxygen ribbons. Therein, the unusual pentanuclear unit comprised of cubane-like [Ln4O4] cluster and the additional Ln (III) center can be observed in complexes 1 and 2, while lanthanide triangle motifs appear in complexes 3 and 4. Static and dynamic magnetic measurements of 1 and 3 have been performed. Both complexes reveal frequency dependence of the out-of-phase signals, suggesting the slow magnetic relaxation behavior for 1 and 3. 3 and 4 exhibit characteristic emissions of the corresponding Er3+ and Yb3+ ions in the NIR region, respectively.