From Layered Structures to Cubic Frameworks: Expanding the Structural Diversity of Uranyl Carboxyphosphonates via the Incorporation of Cobalt

Five heterobimetallic U(VI)/Co(II) carboxyphosphonates have been synthesized under mild hydrothermal conditions by reacting UO3, Co(CH3CO2)(2)center dot 4H(2)O, and triethyl phosphonoacetate. These compounds, Co(H2O)(4)[(UO2)(2)(PO3CH2CO2)(2)(H2O)(2)] (CoUpAA-1), [Co(H2O)(6)][UO2(PO3CH2CO2)](2)center dot 8H(2)O (CoUPAA-2), Co(H2O)(4)UO2(PO3CH2CO2)](2)center dot 4H(2)O (CoUPAA-3), Co(H2O)(4)[(UO2)(6)(PO3CH2CO2)(2)O-2(OH)(3)(H2O)(3)]2 center dot 3H(2)O (CoUPAA-4), and Co-2[(UO2)(6)(PO3CH2CO2)(3)O-3(OH)(H2O)(2)]center dot 16H(2)O (CoUPAA-5), range from two- to three-dimensional structures. CoUPAA-1 to CoUPAA-3 all possess uranyl carboxyphosphonate layers that are separated by the Co(II) cation with varying degrees of hydration. CoUPAA-4 contains both UO7 pentagonal bipyramids and UO8 hexagonal bipyramids within the uranyl carboxyphosphonate plane. Unlike the first four low-symmetry compounds, CoUPAA-5 is a cubic, three-dimensional network with large cavities approximately 16 A in diameter that are filled with cocrystallized water molecules. Differential gas absorption measurements performed on CoUPAA-5 displayed a surface area uptake for CO2 of 40 m(2) g(-1) at 273 K, and no uptake for N-2 at 77 K

Unexpected Structural Complexity in Cesium Thorium Molybdates

Three cesium thorium molybdates [Cs2Th(MoO4)3, Cs2Th3(MoO4)7, and Cs4Th(MoO4)4] were synthesized via the high-temperature solid-state method. Cs2Th(MoO4)3 crystallizes in orthorhombic space group Pnnm, containing [Th(MoO4)3]2– chains extending along the [100] direction. Cs2Th3(MoO4)7 is based on an open framework with channels occupied by Cs+ ions and running parallel through the [100] direction. It is the first case in which thorium atoms coordinate simultaneously in three distinct environments, namely, 7-coordinated pentagonal bipyramid, 8-coordinated square antiprism, and 9-coordinated tricapped trigonal prism. Cs4Th(MoO4)4 is monoclinic, built from [Th(MoO4)4]4– sheets formed by vertex sharing of MoO4 tetrahedra and ThO8 antiprisms. The Raman and infrared spectra were recorded, and the vibrations related to internal and external Mo–O bonds in the MoO42– coordination geometry were discusse