Aminopolyol-Dependent Assembly of Heterometallic Lanthanide-Iron-Oxo Clusters

Lanthanide-iron clusters usually display interesting structures and outstanding magnetic properties. However, due to the high reactivity (acidity) of the Fe3+-H2O bond and the inability to form a terminal oxo ligand, the preparation of high-nuclearity Ln-Fe clusters is a great challenge. Herein, a series of lanthanide-iron-oxo clusters with the formulas [Y6Fe(HL)10(NO3)2(EG)2(mu 3-OH)8(H2O)4]center dot ClO4 center dot N-H2BDEA center dot 2H2O (Y6Fe, 1, H2L = 3-hydroxypivalic acid, EG = ethylene glycol, N-H2BDEA = 2,2 '-(butylimino)diethanol), [Ln8Fe3(H2TEOA)2(HTEOA)2(HL)10(mu 3-OH)9(mu 2-OH)(mu 4-O)2(H2O)4]center dot(NO3)3 center dot xH2O (Ln = Y, x = 13 for 2, Y8Fe3; Ln = Dy, x = 10 for 3, Dy8Fe3; H3TEOA = triethanolamine), and [Ln12Fe14(HL)16(mu 3-OH)20(mu 2-OH)12(mu 4-O)12(H2O)12]center dot(NO3)6 center dot xH2O (Ln = Y, x = 40 for 4, Y12Fe14; Ln = Dy, x = 30 for 5, Dy12Fe14) were obtained by adjusting the pH with different aminopolyols as organic alkalis. Structural analysis showed that a cubane-like unit was the main structural unit in compounds 1-5. Compound 1 was formed by two {Y3Fe(mu 3-OH)4} units with the common vertices, and compounds 2 and 3 were formed by two {Y3Fe(mu 3-OH)3(mu 4-O)} units with the common vertices bridging a quadrilateral unit {Ln2Fe2(mu 3-OH)3(mu 2-OH)}. The basic structural units of cubane-like {Ln2Fe2(mu 3-OH)(mu 4-O)3}, triangular {LnFe2(mu 3-OH)2(mu 4-O)}, and neutral iron-hydroxyl {Fe(mu 3-OH)(mu 2-OH)2} were found in compounds 4 and 5. The universality of building blocks for the assembly has been demonstrated in high-nuclearity lanthanide-iron-oxo clusters. Meanwhile, the structural regulation of the lanthanide-iron-oxo clusters 1-5 was realized by adjusting the pH with different organic alkalis, which provided the reference for the effective synthesis of high-nuclearity lanthanide-iron-oxo clusters. Magnetic studies showed that 3 and 5 displayed a slow magnetic relaxation behavior.