Sandglass-like Ln₉ Nanoclusters with Magnetocaloric Effect and Lanthanide-Centered Luminescence

It is a challenging work to construct high-nuclear lanthanide nanoclusters with desirable magnetocaloric effects. To this end, a series of Ln9 nanoclusters with sandglass-like topological structures have been successfully synthesized under solvothermal conditions by using two different alcoholamine ligands and lanthanide (LnIII) salts, with the molecular formula [Ln9(L1)4(NO3)12(μ3-OH)8(μ4-OH)2(CH3CH2OH)4]·4.5CH3CH2OH·3Et3NH (LnIII = Gd (1-Gd), Eu (1-Eu), Tb (1-Tb)) and [Ln9(L2)8(NO3)8(μ3-OH)8(μ4-OH)2]·NO3 (LnIII = Gd (2-Gd), Eu (2-Eu), Tb (2-Tb)) (H2L1 = N-methyldiethanolamine and HL2 = 2-(2-aminoethoxy)ethanol). It is worth noting that both 1-Gd and 2-Gd exhibit intramolecular antiferromagnetic interactions and show typical magnetocaloric effect behavior. At a magnetic field strength of 7 T and a temperature of 3 K, the values of the −ΔSmmax are 33.65 J kg–1 K–1 for 1-Gd and 25.22 J kg–1 K–1 for 2-Gd. In addition, 1-Eu, 1-Tb, 2-Eu, and 2-Tb exhibit the characteristic luminescence of EuIII and TbIII ions, respectively. For 1-Tb, tunable emission from green to red was achieved by adjusting the doping ratio of lanthanide ions to obtain heterometallic clusters TbxEu9-x, offering the potential for high-fidelity optical barcode applications.