NEW STRUCTURAL TYPES OF CERIUM OXIDE CLUSTERS FROM THE USE OF PHOSPHORUS-BASED LIGANDS

Bradley Russell-Webster, Khalil A. Abboud and George Christou

Department of Chemistry, University of Florida, Gainesville FL 32611-7200 USA

Ceria nanoparticles (CNPs) have a wide range of applications, from catalysis to therapeutic agents and solid oxide fuel cells. They have higher reactivity at lower temperatures than bulk ceria and show face-dependent reactivity. This enhanced reactivity stems from the ability of cerium to cycle between its oxidized and reduced form allowing CNPs to absorb and release oxygen, which is crucial to the reactivity. As the size of nanoparticles decreases, the reactivity increases, but the mechanism by which cerium nanoparticles function is still widely unknown as single-crystal X-ray diffraction techniques are not applicable to characterize them, precluding a detailed understanding of their reactive surface features. Molecular analogues of cerium nanoparticles would offer insight into the mechanisms, and this is driving the current development of methods to synthesize monodisperse, atomically-precise Ce/O/carboxylate nanoclusters that is in progress in our group. Phosphonates (RPO₃^2-) and phosphinates (R₂PO₂^-) have been widely studied with transition metals and lanthanides: phosphinates are similar to carboxylates but differ by size, whereas phosphonates have 3 oxygens and so are able to exhibit a wider range of coordination modes. This study will show how phosphonates and phosphinates lead to new structural types of cerium oxide nanoclusters.