[U(TpMe2)2(bipy)]+: A Cationic Uranium(III) Complex with Single-Molecule-Magnet Behavior

The addition of 2,2′-bipyridine to [U(TpMe2)2I] (1) results in the displacement of the iodide and the formation of the cationic uranium(III) complex [U(TpMe2)2(bipy)]I (2). This compound was isolated as a dark-green solid in good yield and characterized by IR and NMR spectroscopies, and its molecular structure was determined by single-crystal X-ray diffraction. Studies of its magnetic properties revealed a frequency dependence of magnetization with a blocking temperature of 4.5 K and, at lower temperatures, a slow relaxation of magnetization with an energy barrier of 18.2 cm–1, characteristic of single-molecule-magnet behavior.