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.

Incorporation of Cu(2+) ions into nanotubular uranyl diphosphonates.

Three new multidimensional polymetallic uranyl diphosphonates were crystallized under mild hydrothermal conditions: [Cu(H2O)]2{(UO2)4F2[(PO3C6H4)(C6H4PO3H)3]2(bipym)}·6H2O (1), [Cu(H2O)]2{(UO2)4[(C6H4PO3)(C6H4PO3H)]4(bipym)} (2), and Cu{(UO2)(C6H4PO3)2(bipym)}·H2O (3). Compound 1 consists of UO6F pentagonal bipyramids connected by diphosphonate moieties into a tubular channel. The Cu(2+) cations are stabilized between the nanotubular subunits by 2,2'-bipyrimidine (bipym). The structure of 2 is similar to 1, except that it consists of relatively rare UO6 tetragonal bipyramids bridged by diphosphonate groups. Compound 3 also contains UO6 tetragonal bipyramids. Unlike compounds 1 and 2, only two of the tetradentate N atoms of the binucleating bipym group are coordinated. All three compounds show luminescent properties under ambient conditions, with evidence of the characteristic vibronically coupled charge-transfer based uranyl cation emissions.

Hybrid uranium-transition-metal oxide cage clusters.

Transition-metal based polyoxometalate clusters have been known for decades, whereas those built from uranyl peroxide polyhedra have more recently emerged as a family of complex clusters. Here we report the synthesis and structures of six nanoscale uranyl peroxide cage clusters that contain either tungstate or molybdate polyhedra as part of the cage, as well as phosphate tetrahedra. These transition-metal-uranium hybrid clusters exhibit unique polyhedral connectivities and topologies that include 6-, 7-, 8-, 10-, and 12-membered rings of uranyl polyhedra and uranyl ions coordinated by bidentate peroxide in both trans and cis configurations. The transition-metal polyhedra appear to stabilize unusual units built of uranyl polyhedra, rather than templating their formation.

From yellow to black: dramatic changes between cerium(IV) and plutonium(IV) molybdates.

Hydrothermal reactions of CeCl(3) and PuCl(3) with MoO(3) and Cs(2)CO(3) yield surprisingly different results. Ce(3)Mo(6)O(24)(H(2)O)(4) crystallizes as bright yellow plates (space group C2/c, a = 12.7337(7) Å, b = 22.1309(16) Å, c = 7.8392(4) Å, ß = 96.591(4)°, V = 2194.6(2) Å(3)), whereas CsPu(3)Mo(6)O(24)(H(2)O) crystallizes as semiconducting black-red plates (space group C2/c, a = 12.633(5) Å, b = 21.770(8) Å, c = 7.743(7) Å, ß = 96.218(2)°, V = 2117(2) Å(3)). The topologies of the two compounds are similar, with channel structures built from disordered Mo(VI) square pyramids and (RE)O(8) square antiprisms (RE = Ce(IV), Pu(IV)). However, the Pu(IV) compound contains Cs(+) in its channels, while the channels in Ce(3)Mo(6)O(24)(H(2)O)(4) contain water molecules. Disorder and an ambiguous oxidation state of Mo lead to the formula CsPu(3)Mo(6)O(24)(H(2)O), where one Mo site is Mo(V) and the rest are Mo(VI). X-ray absorption near-edge structure (XANES) experiments were performed to investigate the source of the black color of CsPu(3)Mo(6)O(24)(H(2)O). These experiments revealed Pu to be tetravalent, while the strong pre-edge absorption from the distorted molybdate anions leaves the oxidation state ambiguous between Mo(V) and Mo(VI).

Synthesis, structure, and spectroscopy of two ternary uranium(IV) thiophosphates: UP2S9 and UP2S7 containing P2S9(2-) and P2S7(2-) ligands.

The two ternary uranium thiophosphate compounds were isolated from polychalcogenide flux reactions. UP2S9 crystallizes in the tetragonal space group P42/mcm with two formula units per unit cell, where a = 7.762(1) and c = 9.691(3) Å. UP2S7 crystallizes in the orthorhombic space group Fddd with 16 formula units per unit cell, here a = 8.919(3), b = 15.198(4), and c = 30.104(9) Å. Both compounds were characterized through single crystal X-ray, UV-vis-NIR, and Raman spectroscopy. The structures of the two compounds are formed from [US6](8-) chains connected to each other by either the tridentate-chelating P2S9(4-) in UP2S9 or the P2S7(4-) in UP2S7 resulting in 3D frameworks. These two ligands have different geometries, but they exhibit similar coordination modes, comparable to the ethane-like P2S6(4-). The uranium cations in both compounds can be assigned an unambiguous oxidation state of +4. The two compounds are semiconductors with nearly identical band-gaps of 1.41 eV.

Thermochromism, the Alexandrite effect, and dynamic Jahn-Teller distortions in Ho2Cu(TeO3)2(SO4)2.

A 3d-4f heterobimetallic material with mixed anions, Ho2Cu(TeO3)2(SO4)2, has been prepared under hydrothermal conditions. Ho2Cu(TeO3)2(SO4)2 exhibits both thermochromism and the Alexandrite effect. Variable temperature single crystal X-ray diffraction and UV-vis-NIR spectroscopy reveal that changes in the Cu(II) coordination geometry result in negative thermal expansion of axial Cu-O bonds that plays a role in the thermochromic transition of Ho2Cu(TeO3)2(SO4)2. Magnetic studies reveal an effective magnetic moment of 14.97 µB. which has a good agreement with the calculated value of 15.09 µB.

Synthesis, structure, magnetism, and optical properties of Cs2Cu3DyTe4.

CsCu(3)DyTe(4) 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 C2/m with lattice dimensions of a = 16.462(4) Å, b = 4.434(1) Å, c = 8. 881(2) Å, ß = 108.609(12)° with Z = 2. Its crystal structure is dominated by (∞)(2){[Cu(3)DyTe(4)]}(1-) anionic layers separated by Cs(+) cations. The copper cations are disordered over three different tetrahedral sites. The [DyTe(6)](9-) polyhedra form infinite (∞)(1){[DyTe(4)](5-)} chains. Magnetism studies conducted on this semiconductor suggest complex magnetic interactions between the Dy(3+) cations with a strong deviation from Curie-type behavior at low temperatures below 40 K.