Slow Magnetic Relaxation in Uranium(III) and Neodymium(III) Cyclooctatetraenyl Complexes

The
synthesis, structure, and magnetic properties of a uranium­(III)
sandwich complex, [Li­(DME)3]­[UIII(COT″)2] (COT″ = bis­(trimethylsilyl)­cyclooctatetraenyl
dianion), and its coordinatively analogous tetravalent equivalent,
[UIV(COT″)2], were investigated. Additionally,
a full structural and magnetic comparison to the isostructural and
isoelectronic lanthanide complex, [Li­(DME)3]­[NdIII(COT″)2], is provided. DFT calculations reveal
that the UIII complex leads to weaker ligand-to-metal donation
as compared with the tetravalent equivalent complex. Alternating current
magnetic susceptibility results reveal slow magnetic relaxation in
both UIII and NdIII complexes. The enhanced
magnetic performance of the UIII congener further encourages
the use of actinides in the design of single-molecule magnets.