Five Rare μ 4 ‐O‐Centered Ln 6 Clusters with Single‐Molecule Magnet Behavior for Dy 6

Five hexanuclear lanthanide clusters of composition [Ln 6 (μ 4 ‐O) 2 (HCOO) 2 L 4 (HL′) 2 (dmf) 2 ] [Ln=Dy ( 1 ), Er ( 2 ), Ho ( 3 ), Tb ( 4 ), Gd ( 5 ); H 2 L=2‐{[2‐(hydroxymethyl)phenylimino]methyl}‐6‐methoxyphenol; H 3 L′=3‐{[2‐(hydroxymethyl)phenylimino]methyl}benzene‐1,2‐diol; H 3 L′ was derived in situ from the H 2 L ligand] were prepared under solvothermal conditions. The [Ln 6 ] cores of 1 – 5 possess an unprecedented motif, namely, two tetrahedron Ln 4 units sharing an edge and two vertices. The six Ln III ions of 1 – 5 are connected through two μ 4 ‐O anions. Magnetic susceptibility studies reveal that complex  1 exhibits frequency dependence of the alternating current susceptibility typical of single‐molecule magnets. Complex  1 possesses a relatively large energy barrier of 85 K among all of the reported Dy 6 single‐molecule magnets.