Two Luminescent High-Nuclearity Lanthanide Clusters Ln₄₈ (Ln = Eu and Tb) with a Nanopillar Structure

Two nanosize lanthanide clusters Na3[Eu48O6(OH)84(tca)34(gly)12(H2O)22]·2Htca·6Cl·6H2O·NO3 (Eu48) and Na[Tb48O6(OH)84(fca)26(dmp)14(H2O)24]·4Hfca·NO3·8Cl (Tb48) have been isolated in the presence of the monodentate carboxylic acid and tridentate chelate ligands under solvothermal condition. Single-crystal X-ray diffraction analyses indicate that Eu48 and Tb48 feature a nanopillar structure constructed by [Ln3(μ3-OH)4] and [Ln5(μ4-O)(μ3-OH)8] building blocks. In the cavity of the nanopillar, two kinds of anion templates, i.e., NO3– and Cl–, exist, which connect with the nanopillar by hydrogen bond interactions. As the hitherto highest-nuclearity Eu and Tb clusters, the solid-state photoluminescence properties of Eu48 (λEx = 365 nm) and Tb48 (λEx = 370 nm) display dual emission from the characteristic emissions of Eu3+ and Tb3+ ions and weak ligand emissions. Nevertheless, the Eu3+-centered emission was shown under 395 nm excitation with no discernible ligand emission. Moreover, the luminescence properties of Eu48 and Tb48 display a response to temperature. With the temperature lowering, the emission peak intensities gradually increase, and good linker relations exist in the range of 118–298 K. This work provides a reference for choosing suitable ligands to synthesize the high-nuclearity luminescent lanthanide nanoclusters.