Single-molecule magnet behavior in heterometallic decanuclear [Ln 2 Fe 8 ] (Ln = Y, Dy, Ho, Tb, Gd) coordination clusters.

Five decanuclear lanthanide-iron clusters, formulated as [Ln 2 Fe 8 (hmp) 10 (μ 2 -OH) 4 (μ 3 -OH) 2 (μ 4 -O) 4 (H 2 O) 6 ]·6ClO 4 · x H 2 O ( x ≈ 8, Ln = Y for 1; x ≈ 6, Ln = Dy for 2; x ≈ 6, Ln = Ho for 3; x ≈ 7, Ln = Tb for 4; x ≈ 7, Ln = Gd for 5, Hhmp = 2-(hydroxymethyl)pyridine), have been synthesized and structurally characterized. Single-crystal structural analysis reveals that the cluster consists of six face-sharing defective cubane units. Dynamic magnetic investigations indicated that cluster 2 exhibits single-molecule magnet behavior under a zero dc field eliciting an effective energy barrier of U eff = 17.76 K and a pre-exponential factor of τ 0 = 7.93 × 10 -8 s. Investigation of the performance of a series of Fe III -Dy III SMMs indicates that the relatively low energy barrier in 2 is associated with the weak ferromagnetic coupling between Fe III and Dy III ions, while the strength of ferromagnetic interaction in these clusters is mainly related to the bond distances between Dy III and O atoms coordinated to Fe III ions. Clusters 3 and 4 exhibit similar dual relaxation pathways under their respective optimal external applied dc field, where the direct relaxation process occurs in the low-frequency area, which impedes the extraction of the U eff , while the secondary relaxation process appears at a higher frequency, which is probably a connection with intermolecularly driven relaxation. Our findings offer a magneto-structural correlation model for further investigating the single-molecule magnet behavior in lanthanide-iron systems.