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

Abstract

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(μ3-OH)8(H2O)4]·ClO4·N-H2BDEA·2H2O (Y6Fe, 1, H2L = 3-hydroxypivalic acid, EG = ethylene glycol, N-H2BDEA = 2,2'-(butylimino)diethanol), [Ln8Fe3(H2TEOA)2(HTEOA)2(HL)10(μ3-OH)9(μ2-OH)(μ4-O)2(H2O)4]·(NO3)3·xH2O (Ln = Y, x = 13 for 2, Y8Fe3; Ln = Dy, x = 10 for 3, Dy8Fe3; H3TEOA = triethanolamine), and [Ln12Fe14(HL)16(μ3-OH)20(μ2-OH)12(μ4-O)12(H2O)12]·(NO3)6·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(μ3-OH)4} units with the common vertices, and compounds 2 and 3 were formed by two {Y3Fe(μ3-OH)3(μ4-O)} units with the common vertices bridging a quadrilateral unit {Ln2Fe2(μ3-OH)3(μ2-OH)}. The basic structural units of cubane-like {Ln2Fe2(μ3-OH)(μ4-O)3}, triangular {LnFe2(μ3-OH)2(μ4-O)}, and neutral iron-hydroxyl {Fe(μ3-OH)(μ2-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.