Dark Shadows Concordance 1795

Sep-7

Layered Uranyl Coordination Polymers Rigidly Pillared by Diphosphonates

The hydrothermal reaction of uranyl nitrate and 1,4-benzenebisphosphonic acid in the presence of monovalent and divalent metal hydroxides results in the formation of four new uranyl coordination polymers: Ag₂{(UO₂)­[C₆H₄(PO₃H)₂]₂} <b>(AgUbbp)</b>, Cs­{(UO₂)­[C₆H₄(PO₃H_0.5)₂]} <b>(CsUbbp)</b>, [Ba­(H₂O)₃]­{(UO₂)₃[C₆H₄(PO₃)₂]₂(O)}·5­(H₂O) (<b>BaUbbp</b>), and [Sr­(H₂O)₃]­{(UO₂)₂[C₆H₄(PO₃)₂]­(OH)₂(H₂O)}·3­(H₂O) (<b>SrUbbp</b>). <b>AgUbbp</b> and <b>CsUbbp</b> complexes are constructed from UO₆ units with tetragonal bipyramidal coordination geometries, whereas <b>BaUbbp</b> and <b>SrUbbp</b> complexes contain UO₇ units with pentagonal bipyramidal coordination environments. The pH and the monovalent/divalent metal cations have significant effects on the topology of these structures. These compounds fluoresce at room temperature owing to emission from the uranyl units

Layered Uranyl Coordination Polymers Rigidly Pillared by Diphosphonates

The hydrothermal reaction of uranyl nitrate and 1,4-benzenebisphosphonic acid in the presence of monovalent and divalent metal hydroxides results in the formation of four new uranyl coordination polymers: Ag₂{(UO₂)­[C₆H₄(PO₃H)₂]₂} <b>(AgUbbp)</b>, Cs­{(UO₂)­[C₆H₄(PO₃H_0.5)₂]} <b>(CsUbbp)</b>, [Ba­(H₂O)₃]­{(UO₂)₃[C₆H₄(PO₃)₂]₂(O)}·5­(H₂O) (<b>BaUbbp</b>), and [Sr­(H₂O)₃]­{(UO₂)₂[C₆H₄(PO₃)₂]­(OH)₂(H₂O)}·3­(H₂O) (<b>SrUbbp</b>). <b>AgUbbp</b> and <b>CsUbbp</b> complexes are constructed from UO₆ units with tetragonal bipyramidal coordination geometries, whereas <b>BaUbbp</b> and <b>SrUbbp</b> complexes contain UO₇ units with pentagonal bipyramidal coordination environments. The pH and the monovalent/divalent metal cations have significant effects on the topology of these structures. These compounds fluoresce at room temperature owing to emission from the uranyl units

Periodic Trends in Hexanuclear Actinide Clusters

Four new Th­(IV), U­(IV), and Np­(IV) hexanuclear clusters with 1,2-phenylenediphosphonate as the bridging ligand have been prepared by self-assembly at room temperature. The structures of Th₆Tl₃[C₆H₄(PO₃)­(PO₃H)]₆(NO₃)₇(H₂O)₆·(NO₃)₂·4H₂O (<b>Th6-3</b>), (NH₄)_8.11­Np₁₂Rb_3.89[C₆H₄(PO₃)­(PO₃H)]₁₂(NO₃)₂₄·15H₂O (<b>Np6-1</b>), (NH₄)₄U₁₂Cs₈[C₆H₄(PO₃)­(PO₃H)]₁₂(NO₃)₂₄·18H₂O (<b>U6-1</b>), and (NH₄)₄­U₁₂Cs₂­[C₆H₄(PO₃)­(PO₃H)]₁₂(NO₃)₁₈·40H₂O (<b>U6-2</b>) are described and compared with other clusters of containing An­(IV) or Ce­(IV). All of the clusters share the common formula M₆(H₂O)_<i>m</i>[C₆H₃(PO₃)­(PO₃H)]₆(NO₃)_<i>n</i>^{(6–<i>n</i>)} (M = Ce, Th, U, Np, Pu). The metal centers are normally nine-coordinate, with five oxygen atoms from the ligand and an additional four either occupied by NO₃^– or H₂O. It was found that the Ce, U, and Pu clusters favor both <i>C</i>_3<i>i</i> and <i>C</i>_<i>i</i> point groups, while Th only yields in <i>C</i>_<i>i</i>, and Np only <i>C</i>_3<i>i</i>. In the <i>C</i>_3<i>i</i> clusters, there are two NO₃^– anions bonded to the metal centers. In the <i>C</i>_<i>i</i> clusters, the number of NO₃^– anions varies from 0 to 2. The change in the ionic radius of the actinide ions tunes the cavity size of the clusters. The thorium clusters were found to accept larger ions including Cs⁺ and Tl⁺, whereas with uranium and later elements, only NH₄⁺ and/or Rb⁺ reside in the center of the clusters

Periodic Trends in Hexanuclear Actinide Clusters

Four new Th­(IV), U­(IV), and Np­(IV) hexanuclear clusters with 1,2-phenylenediphosphonate as the bridging ligand have been prepared by self-assembly at room temperature. The structures of Th₆Tl₃[C₆H₄(PO₃)­(PO₃H)]₆(NO₃)₇(H₂O)₆·(NO₃)₂·4H₂O (<b>Th6-3</b>), (NH₄)_8.11­Np₁₂Rb_3.89[C₆H₄(PO₃)­(PO₃H)]₁₂(NO₃)₂₄·15H₂O (<b>Np6-1</b>), (NH₄)₄U₁₂Cs₈[C₆H₄(PO₃)­(PO₃H)]₁₂(NO₃)₂₄·18H₂O (<b>U6-1</b>), and (NH₄)₄­U₁₂Cs₂­[C₆H₄(PO₃)­(PO₃H)]₁₂(NO₃)₁₈·40H₂O (<b>U6-2</b>) are described and compared with other clusters of containing An­(IV) or Ce­(IV). All of the clusters share the common formula M₆(H₂O)_<i>m</i>[C₆H₃(PO₃)­(PO₃H)]₆(NO₃)_<i>n</i>^{(6–<i>n</i>)} (M = Ce, Th, U, Np, Pu). The metal centers are normally nine-coordinate, with five oxygen atoms from the ligand and an additional four either occupied by NO₃^– or H₂O. It was found that the Ce, U, and Pu clusters favor both <i>C</i>_3<i>i</i> and <i>C</i>_<i>i</i> point groups, while Th only yields in <i>C</i>_<i>i</i>, and Np only <i>C</i>_3<i>i</i>. In the <i>C</i>_3<i>i</i> clusters, there are two NO₃^– anions bonded to the metal centers. In the <i>C</i>_<i>i</i> clusters, the number of NO₃^– anions varies from 0 to 2. The change in the ionic radius of the actinide ions tunes the cavity size of the clusters. The thorium clusters were found to accept larger ions including Cs⁺ and Tl⁺, whereas with uranium and later elements, only NH₄⁺ and/or Rb⁺ reside in the center of the clusters

A₆U₃Sb₂P₈S₃₂ (A = Rb, Cs): Quinary Uranium(IV) Thiophosphates Containing the [Sb(PS₄)₃]^6– Anion

The reaction of A₂S₃/U/P₂S₅/S at 500 °C affords the quinary U­(IV) thiophosphates A₆U₃Sb₂P₈S₃₂ (A = Rb, Cs). These compounds contain {U₃(PS₄)₂[Sb­(PS₄)₃]₂}^6– layers separated by alkali metal cations. The layers are composed of trimeric uranium units connected to each other by the thiophosphato-antimonite anion, [Sb­(PS₄)₃]^6–. This unit contains a central Sb­(III) cation bound by three [PS₄]^3– anions, creating a trigonal pyramidal environment around Sb­(III). Each uranium cation is surrounded by eight sulfides in a distorted square antiprism that shares two edges with two other US₈ units to form a trimeric [U₃S₁₈]^24– cluster. Magnetic susceptibility measurements indicate that the close proximity of the U­(IV) within these clusters leads to antiferromagnetic ordering at 53 K. Reflectance spectroscopy indicates that these compounds are semiconductors with a band gap of 1.48 eV

A₆U₃Sb₂P₈S₃₂ (A = Rb, Cs): Quinary Uranium(IV) Thiophosphates Containing the [Sb(PS₄)₃]^6– Anion

The reaction of A₂S₃/U/P₂S₅/S at 500 °C affords the quinary U­(IV) thiophosphates A₆U₃Sb₂P₈S₃₂ (A = Rb, Cs). These compounds contain {U₃(PS₄)₂[Sb­(PS₄)₃]₂}^6– layers separated by alkali metal cations. The layers are composed of trimeric uranium units connected to each other by the thiophosphato-antimonite anion, [Sb­(PS₄)₃]^6–. This unit contains a central Sb­(III) cation bound by three [PS₄]^3– anions, creating a trigonal pyramidal environment around Sb­(III). Each uranium cation is surrounded by eight sulfides in a distorted square antiprism that shares two edges with two other US₈ units to form a trimeric [U₃S₁₈]^24– cluster. Magnetic susceptibility measurements indicate that the close proximity of the U­(IV) within these clusters leads to antiferromagnetic ordering at 53 K. Reflectance spectroscopy indicates that these compounds are semiconductors with a band gap of 1.48 eV

Synthesis, Structure, Magnetism, and Optical Properties of Cs₂Cu₃DyTe₄

CsCu₃DyTe₄ was prepared by reacting copper, dysprosium, and tellurium with cesium azide at 850 °C in a fused silica ampule. This new telluride crystallizes in the monoclinic space group <i>C</i>2/<i>m</i> with lattice dimensions of <i>a</i> = 16.462(4) Å, <i>b</i> = 4.434(1) Å, <i>c</i> = 8. 881(2) Å, β = 108.609(12)° with <i>Z</i> = 2. Its crystal structure is dominated by _∞²{[Cu₃DyTe₄]}^1– anionic layers separated by Cs⁺ cations. The copper cations are disordered over three different tetrahedral sites. The [DyTe₆]^9– polyhedra form infinite _∞¹{[DyTe₄]^5–} chains. Magnetism studies conducted on this semiconductor suggest complex magnetic interactions between the Dy³⁺ cations with a strong deviation from Curie-type behavior at low temperatures below 40 K

Uranyl Heteropolyoxometalate: Synthesis, Structure, and Spectroscopic Properties

A novel uranium heteropolyoxometalate, [H₃O]₄[Ni­(H₂O)₃]₄{Ni­[(UO₂)­(PO₃C₆H₄CO₂)]₃­(PO₄H)}₄·2.72H₂O, has been prepared under mild hydrothermal conditions using the diethyl­(2-ethoxycarbonylphenyl)­phosphonate ligand and <i>in situ</i> ligand synthesis of the HPO₄^2– anion. The cluster is derived from a common UO₇, pentagonal bipyramid and is constructed by employing nickel­(II) metal ions as linkers. The 3d–5f heteropolyoxometalate core incorporates 12 classical pentagonal uranyl groups and four Ni²⁺ octahedral units

Understanding the Scarcity of Thorium Peroxide Clusters

The reaction of Th­(NO₃)₄·5H₂O with 3 equiv of 2,2′,6′,2″-terpyridine (terpy) in a mixture of acetonitrile and methanol results in formation of the trinuclear thorium peroxide cluster [Th­(O₂)­(terpy)­(NO₃)₂]₃. This cluster is assembled via bridging by μ–η²:η² peroxide anions between thorium centers. It decomposes upon removal from the mother liquor to yield Th­(terpy)­(NO₃)₄ and Th­(terpy)­(NO₃)₄(EtOH). The peroxide formation appears to be radiolytic in origin and is, most likely, generated from radiolysis of water by short-lived daughters generated from ²³²Th decay. This cluster does not form when freshly recrystallized Th­(NO₃)₄·5H₂O is used as the starting material and requires an aged source of thorium. Analysis of the bonding in these clusters shows that, unlike uranium­(VI) peroxide interactions, thorium­(IV) complexation by peroxide is quite weak and largely ionic. This explains its much lower stability, which is more comparable to that observed in similar zirconium­(IV) peroxide clusters