Heterometallic Fe2II-UV and Ni2II-UV Exchange-Coupled Single-Molecule Magnets: Effect of the 3 d Ion on the Magnetic Properties.

Uranium-based compounds have been put forward as ideal candidates for the design of single-molecule magnets (SMMs) with improved properties, but to date, only two examples of exchange-coupled 3d-5f SMM containing uranium have been reported and both are based on the MnII ion. Here we have synthesized the first examples of exchange-coupled uranium SMMs based on FeII and NiII. The SMM behavior of these complexes containing a quasi linear {MOUOM} core arises from intramolecular FeU and NiU exchange interactions combined with the high Ising anisotropy of the uranyl(V) moiety. The measured values of the relaxation barrier (53.9±0.9 K in the UFe2 complex and of 27.4±0.5 K in the UNi2 complex) show clearly the dependency on the spin value of the transition metal, providing important new information for the future design of improved uranium-based SMMs. [ABSTRACT FROM AUTHOR]