Beauty, Symmetry, and Magnetocaloric EffectFour-Shell Keplerates with 104 Lanthanide Atoms

The
hydrolysis of Ln­(ClO4)3 in the presence
of acetate leads to the assembly of the three largest known lanthanide-exclusive
cluster complexes, [Nd104(ClO4)6(CH3COO)60(μ3-OH)168(μ4-O)30(H2O)112]·(ClO4)18·(CH3CH2OH)8·xH2O (1, x ≈ 158) and [Ln104(ClO4)6(CH3COO)56(μ3-OH)168(μ4-O)30(H2O)112]·(ClO4)22·(CH3CH2OH)2·xH2O (2, Ln = Nd; 3, Ln = Gd; x ≈
140). The structure of the common 104-lanthanide core, abbreviated
as Ln8@Ln48@Ln24@Ln24,
features a four-shell arrangement of the metal atoms contained in
an innermost cube (a Platonic solid) and, moving outward, three Archimedean
solids: a truncated cuboctahedron, a truncated octahedron, and a rhombicuboctahedron.
The magnetic entropy change of ΔSm = 46.9 J kg–1 K–1 at 2 K for
ΔH = 7 T in the case of the Gd104 cluster is the largest among previously known lanthanide-exclusive
cluster compounds.