35 research outputs found
Supramolecular Assembly of U(IV) Clusters and Superatoms
No full textSuperatoms are nanometer-sized molecules or particles that can form ordered lattices, mimicking their atomic counterparts. Hierarchical assembly of superatoms gives rise to emergent properties in superlattices of quantum-dots, p-block clusters, and fullerenes. Here, we introduce a family of uranium-oxysulfate cluster anions whose hierarchical assembly in water is controlled by two parameters; acidity and the countercation. In acid, larger LnIII (Ln=La-Ho) link hexamer (U6) oxoclusters into body-centered cubic frameworks, while smaller LnIII (Ln=Er-Lu &Y) promote linking of fourteen U6-clusters into hollow superclusters (U84 superatoms). U84 assembles into superlattices including cubic-closest packed, body-centered cubic, and interpenetrating networks, bridged by interstitial countercations, and U6-clusters. Divalent transition metals (TM=MnII and ZnII), with no added acid, charge-balance and promote the fusion of 10 U6 and 10 U-monomers into a wheel–shaped cluster (U70). Dissolution of U70 in organic media reveals (by small-angle Xray scattering) that differing supramolecular assemblies are accessed, controlled by TM-linking of U70-clusters. <br /
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Using Metal-Oxo Clusters to Expand Actinide Chemistry
No full textA molecular approach to metal oxides allows to the study to fundamental bonding and formation behavior for such metals. Moreover, the molecular nature of such oxides or metal-oxo clusters allows the possibility of exploitation of the properties of the parent oxides. The tetravalent metals, in specific, (M=Zr, Hf, Ce, Th, U, Np, Pu) have been chemist’s choice in bottoms-up material design, catalysis, and elucidating reaction pathways in nature and in synthesis. Actinide-oxide clusters, colloids, and materials are particularly sought after and studied for 1) nuclear materials applications, 2) understanding environmental fate and transport of actinides, and 3) exploring the complex bonding behavior of open-shell f-elements. Synthesis of these metal-oxo cluster depend on controlling the hydrolysis and condensation reactions the govern oxide formation. Herein we demonstrate control over the reactions can be met by using counterions and strongly coordinating oxo-anions. As such we demonstrate three new crystal structure families, M6, M84, and M70, and how to access them. The study using three tetravalent metals (Th, U, Ce) additionally allows to probe differences between the metals in the tetravalent group
Supramolecular Assembly of CeIV-Oxo Sulfate Torus with Transition Metal Countercations
No full textMIV molecular oxo-clusters of the f- and d-block
(M=Zr, Hf, Ce, Th, U, Np, Pu) have been prolific in bottoms-up material design,
catalysis, as well as understanding metal oxide assembly, dissolution and
surface reactivity in nature and in synthesis. Here we introduce Ce70,
a new CeIV wheel-shaped oxo-cluster, [CeIV(OH)36(O)64(SO4)60(H2O)10]4-,
isostructural with prior-reported U70. Like U70, Ce70
crystallizes into intricate frameworks with divalent transition metal
counter-cations (TMII), and also CeIV-monomer and sulfate
addenda ions
Chemical diversity and versatility of polyoxometalate ligands: homologous series of twenty-five new structures with polyoxometalates binding to alkali, alkaline earth, lanthanide, and actinide ions
No full textCoordination chemistry trends across the periodic table are often difficult to probe experimentally due to limitations in finding a versatile but consistent chelating platform able to accommodate various elements without changing its coordination mode. Herein, we present new metal-ligand systems covering a wide range of ionic radii, charges, and elements. Five different ligands derived from the Keggin structure (HBW11O398-, PW11O397-, SiW11O399-, GeW11O399-, and GaW11O399-) were successfully crystalized with six different cations (Na+, Sr2+, Ba2+, La3+, Ce4+, Th4+) and characterized by single crystal XRD. Twenty-five new compounds were obtained by using Cs+ as counterion, yielding a consistent base formula of Csx[M(XW11O39)2]·nH2O. Despite having a similar first-coordination sphere geometry (i.e., 8-coordinated), the nature of the central cation was found to impact the long-range geometry of the complexes. This unique crystallographic dataset shows that, despite the traditional consensus, the local geometry of the cation (i.e., metal-oxygen bond distance) is not enough to depict the full impact of the complexed metal ion. The bending and twisting of the complexes, as well as ligand-ligand distances were all impacted by nature of the central cation. We also observed that counterions play a critical role by stabilizing the geometry of the M(XW11)2 complex and directing complex-complex interactions in the lattice. We also define certain structural limits for this type of complex, with the large Ba2+ ion seemingly approaching those limits. This study thus lays the ground for capturing the coordination chemistry of other, rarer, elements across the periodic table such as Ra2+, Ac3+, Bk4+, Cf3+, etc
Synthesis and structural characterization of a hydrated sodium–caesium tetracosatungstate(VI), Na5Cs19[W24O84]·21H2O
No full textCrystal formation of pentasodium nonadecacesium tetracosatungstate(VI) heneikosahydrate, Na5Cs19[W24O84]·21H2O, was successfully achieved by the conversion of [H2W12O42]10− through the addition of excess Cs+. The crystal structure comprising the toroidal isopolyoxidometalate is presented, as well as its Raman spectrum. Na5Cs19(H2O)21W24O84 crystallizes in the rhombohedral space group R\overline{3} with an obverse centering. The title compound represents the addition of a new member to the isopolytungstate family with mixed alkali counter-ions and contains rarely observed five-coordinate tungsten(VI) atoms in the [W24O84]24− anion (site symmetry C3i) arising from the conversion mediated by Cs+ counter-ions
