Uranyl peroxide polyhedra are known to self-assemble into complex closed clusters with fullerene and other topologies containing as many as 60 polyhedra. Here clusters containing 20 uranyl pentagonal triperoxides have been isolated and characterized that assume the smallest possible fullerene topology consisting only of 12 pentagons. Oxalate has been used to crystallize fragments of larger uranyl peroxide clusters, and these fragments and other known structures indicate that the U-O(2)-U dihedral angle is inherently bent. Such bending is thought to be essential in directing the self-assembly of uranyl peroxide polyhedra into closed clusters.

C U soon: Clusters containing 60, 44, and 36 uranyl peroxide hydroxide polyhedra (see picture) adopt fullerene topologies of maximum symmetry. The largest of these, denoted U60, is topologically identical to C(60) with no pentagonal adjacencies and the highest possible symmetry. U44 adopts the topology with maximum symmetry rather than that with the lowest number of pentagonal adjacencies.

Nanotubular materials have unique water transport and storage properties that have the potential to advance separations, catalysis, drug delivery, and environmental remediation technologies. The development of novel hybrid materials, such as metal-organic nanotubes (MONs), is of particular interest, as these materials are amenable to structural engineering strategies and may exhibit tunable properties based upon the presence of inorganic components. A novel metal-organic nanotube, (C4H12N2)(0.5)[(UO2)(Hida)(H2ida)]·2H2O (UMON) (ida = iminodiacetate), that demonstrates the possibilities of these types of hybrid compounds has been synthesized via a supramolecular approach. Single-crystal X-ray diffraction of the compound revealed stacked macrocyclic arrays that contain highly ordered water molecules with structural similarities to the "ice channels" observed in single-walled carbon nanotubes. Nanoconfinement of the water molecules may be the cause of the unusual exchange properties observed for UMON, including selectivity to water and reversible exchange at low temperature (37 °C). Similar properties have not been reported for other inorganic or hybrid compounds and indicate the potential of MONs as advanced materials.

The hydrolysis of aluminum and formation of polynuclear species, such as the Keggin-type polycations, impacts the chemical and physical properties of the resulting aluminum oxide and hydroxide materials. Despite years of study, only a handful of Keggin-type species have been identified, hampering efforts toward a molecular-level understanding of the mechanisms of condensation. To improve the crystallization of Keggin-type polyaluminum cations, a supramolecular approach using 2,6-napthalene disulfonate (2,6-NDS) was proposed herein for the isolation of novel compounds. The present study describes the successful synthesis and structural characterization of three Keggin-type polyaluminum compounds, including (Na(Al(μ 4 -O 4 )Al 12 (μ-OH) 24 (H 2 O)) 12 (2,6NDS) 4 (H2O) 13.5 (δ-Al 13 ), ( Al2 (μ 4 -O 8 )(Al 28 (μ 2 -OH) 56 (H 2 O) 26 )(2,6NDS) 8 Cl 2 (H 2 O) 40 (Al 30 ), and a new polycation, (Al 2 (μ 4 -O 8 )(Al 24 (μ 2 -OH) 50 (H 2 O) 20 )(2,6NDS) 6 (H 2 O) 12.4 (Al 26). Additional chemical characterization of the compounds, particularly 27 Al-NMR, suggests that identifying the Al 26 polycation in aqueous solutions may be difficult due to structural similarities to the δ-Al 13 moiety. The structural characterization of novel Keggin-type aluminum polycations is important for a complete understanding of aluminum hydrolysis in aqueous solutions, and organosulfonates represent a viable approach for the crystallization of new polynuclear species.

Four self-assembling clusters of uranyl peroxide polyhedra have been formed in alkaline aqueous solutions and structurally characterized. These clusters consist of 28, 30, 36 and 44 uranyl polyhedra and exhibit complex new topologies. Each has a structure that contains topological squares, pentagons and hexagons. Analysis of possible topologies within boundary constraints indicates a tendency for adoption of higher symmetry topologies in these cases. Small angle X-ray scattering data demonstrated that crystals of one of these clusters can be dissolved in ultrapure water and that the clusters remain intact for at least several days.