Heterometallic Cubanes: Syntheses, Structures, and Magnetic Properties of Lanthanide(III)-Nickel(II) Architectures

Reactions of lanthanide(III) perchlorate (Ln = Dy, Tb, and Gd), nickel(II) acetate, and ditopic ligand 2-(benzothiazol-2-ylhydrazonomethyl)-6-methoxyphenol (H2L) in a mixture of methanol and acetone in the presence of NaOH resulted in the successful assembly of novel Ln(2)Ni(2) heterometallic clusters representing a new heterometallic 3d-4f motif. Single-crystal X-ray diffraction reveals that all compounds are isostructural, with the central core composed of distorted [Ln(2)Ni(2)O(4)] cubanes of the general formula [Ln(2)Ni(2)(mu(3)-OH)(2)(OH)(OAc)(4)(HL)(2)(MeOH)(3)](ClO4)center dot 3MeOH [Ln = Dy (1). Tb (2), and Gd (3)]. The magnetic properties of all compounds have been investigated. Magnetic analysis on compound 3 indicates ferromagnetic Gd center dot center dot center dot Ni exchange interactions competing with antiferromagnetic Ni center dot center dot center dot Ni interactions. Compound 1 displays slow relaxation of magnetization, which is largely attributed to the presence of the anisotropic Dy-III ions, and thus represents a new discrete [Dy2Ni2] heterometallic cubane exhibiting probable single-molecule magnetic behavior.