The radially diffuse 5f orbitals of the actinides impart them with magnetic and electronic properties that make them appealing for study as single-molecule magnets. This is because their large instrinsic magnetic anisotropies—which are necessary for slow magnetic relaxation—can be supplemented by strong magnetic exchange interactions arising from covalent metal-ligand bonding.<br/>Here we present our recent work on a highly anisotropic uranium(III) metallocenium cation that exhibits significantly slower magnetic relaxation than that observed in other mononuclear actinide complexes, which we attribute to the constrained metal-ligand vibrational modes within the molecule. Furthermore, we show our synthetic work on designing multinuclear uranium metallocene clusters with redox-active organic bridges, such as [2,2′-bipyrimidine] and [2,3,5,6-tetra(2-pyridyl)pyrazine]. Cyclic voltammetry studies on the latter complex reveal remarkable electrochemical robustness and suggest strong electronic communication between uranium atoms. Of the several redox products possible in this latter system, a radical-bridged diuranium complex has been isolated and shows slow magnetic relaxation under zero and applied fields. The structural, magnetic, and electrochemical properties of these clusters will be presented.

Slow magnetic relaxation in mono- and multinuclear uranium metallocene complexes

2019 Fall National Meeting

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