Dynamics of Uranyl Peroxide Nanocapsules

Discrete aqueous metal oxide polyionic clusters that
include aluminum
polycations, transition-metal polyoxometalates, and the actinyl peroxide
clusters have captivated the interest of scientists in the realm of
both their fundamental and applied chemistries. Yet the counterions
for these polycations or polyanions are often ignored, even though
they are imperative for solubility, crystallization, purification,
and even templating cluster formation. The actinyl peroxide clusters
have counterions not only external, but internal to the hollow peroxide
capsules. In this study, we reveal the dynamic behavior of these internal
alkali counterions via solid-state and liquid NMR experiments. These
studies on two select cluster geometries, those containing 24 and
28 uranyl polyhedra, respectively, show that the capsules-like clusters
are not rigid entities. Rather, the internal alkalis both have mobility
inside the capsules, as well as exchange with species in the media
in which they are dissolved. The alkali mobilities are affected by
both what is inside the clusters as well as the composition of the
dissolving medium.