From Two-Dimensional Layers to Three-Dimensional Frameworks: Expanding the Structural Diversity of Uranyl Compounds by Cation–Cation Interactions

Abstract

Two uranyl tungstates, Cs 4 [(UO 2 ) 4 (WO 5 )-(W 2 O 8 )O 2 ] (CsUW-1) and Cs 4 [(UO 2 ) 7 (WO 5 ) 3 O 3 ] (CsUW-2), were obtained via the high-temperature solid-state synthesis method by reacting uranyl nitrate with WO 3 in the presence of cesium nitrate. CsUW-1 crystallizes in space group P2 1 /n, adopting a two-dimensional (2D) sheet structure. CsUW-2 forms a three-dimensional (3D) framework constructed by complex 2D sheets linked by cation−cation interactions of UO 2 2+ groups. The cation−cation interactions fragment presented in CsUW-2 involves the 2D → 3D transformation of the uranyl tungstate network and acts as an intermediate part by bridging the structures of CsUW-1 and CsUW-2. We demonstrate that the chemical and structural transformation from CsUW-1 to CsUW-2 is possible via adding a suitable amount of UO 3 oxide. In addition, the differential scanning calorimetry-thermogravimetric technique was carried out to gain insight into the thermal behavior of the synthesized compounds. Raman spectra of titled compounds were obtained and analyzed for signature peaks.

Detection and identification of solids, surfaces, and solutions of uranium using vibrational spectroscopy

“…Cation-cation interactions cause the uranyl bond engaged in this interaction to weaken and the ν 1 band to red shift. Xiao et al [118] reported Raman spectra of the two uranyl tungstate compounds, Cs 4 [(UO 2 ) 4 (WO 5 )W 2 O 8 )O 2 ] and Cs 4 [(UO 2 ) 7 (WO 5 ) 3 O 3 ]. These compounds contain cation-cation interactions in four of the seven crystallographically unique U(VI) polyhedra.…”

“…Substantial elongation of the uranyl bonds (1.805–1.821 Å) is observed with Cs 4 [(UO 2 ) 4 (WO 5 )W 2 O 8 )O 2 ] while there is more variability (1.76–1.99 Å) for Cs 4 [(UO 2 ) 7 (WO 5 ) 3 O 3 ]. Concurrently, the Raman spectra reveal two uranyl vibrational modes [118]. The first is located at 828 cm −1 for unperturbed uranyl bonds and a red shifted mode between ~780 and 760 cm −1 for the uranyl oxo bonds engaged in cation-cation interactions.…”

Non-covalent interactions of uranyl complexes: a theoretical study

“…Cation-cation interactions have been found to extend this dimensionality: selected examples include [UO2(NO2TA)2(H2O)] (NO2TA = 2-nitroterephthalic acid) 7 or the purely inorganic Cs4[(UO2)7(WO5)3O3]. 8 More recently the supramolecular chemists arsenal of non-covalent interactions have featured in uranyl crystal chemistry. Hydrogen bonding between a [UO2Cl4] 2anion and bipyridinium cations afford various topologies according to the nature of the cation.…”

Structural and Spectroscopic Investigation of Novel 2D and 3D Uranium Oxo-Silicates/Germanates and Some Statistical Aspects of Uranyl Coordination in Oxo-Salts

“…The Raman spectrum of K 4 (UO 2 ) 2 Si 8 O 20 ·4H 2 O in the 100–3600 cm –1 region is shown in Figure and exhibits a strong peak at 781 cm –1 , which corresponds to the symmetric ν 1 mode of (UO 2 ) 2+ cations (Table S4). Another shoulder at 751 cm –1 is also attributed to the ν 1 (UO 2 ) 2+ vibrations. , The ν 3 modes of (UO 2 ) 2+ ions can be found at 813 cm –1 , , and the ν 2 (UO 2 ) 2+ modes are located at 223 and 297 cm –1 . The Raman spectrum in the range of 400–700 cm –1 and high frequency range of 950–1100 cm –1 illustrates a large number of peaks owing to the existing of complex oxo-silicate fragments in the structure.…”

“…35 Another shoulder at 751 cm −1 is also attributed to the ν 1 (UO 2 ) 2+ vibrations. 35,36 The ν 3 modes of (UO 2 ) 2+ ions can be found at 813 cm −1 , 36,37 and the ν 2 (UO 2 ) 2+ modes are located at 223 and 297 cm −1 . 38 The Raman spectrum in the range of 400−700 cm −1 and high frequency range of 950−1100 cm −1 illustrates a large number of peaks owing to the existing of complex oxo-silicate fragments in the structure.…”