Linear Alkyl Diamine-Uranium-Phosphate Systems: U(VI) to U(IV) Reduction with Ethylenediamine

Abstract

Mild-hydrothermal reactions in acidic medium using 1,3-diaminopropane, 1,4-diaminobutane, and 1,5-diaminopentane as structure directing agents led to three-dimensional (3D) uranyl phosphates (CH₂)₃(NH₃)₂{[(UO₂)(H₂O)][(UO₂)(PO₄)]₄} (C3U5P4), (CH₂)₄(NH₃)₂{[(UO₂)(H₂O)][(UO₂)(PO₄)]₄} (C4U5P4) and (CH₂)5(NH₃)₂{[(UO₂)(H₂O)][(UO₂)(PO₄)]₄} (C5U5P4). The structures of (C4U5P4) and (C5U5P4) were solved in the space group Cmc2₁ using single-crystal X-ray diffraction data. The compounds are isostructural to the corresponding uranyl vanadates and contain the same 3D inorganic framework built from uranyl-phosphate layers of uranophane-type anion topology pillared by [UO₆(H₂O)] pentagonal bipyramids. In neutral or basic medium the alkyl diamines decompose to give ammonium uranyl phosphate trihydrate. In the same conditions by using ethylenediamine, unexpected reduction of uranium(VI) to uranium(IV) occurs leading to the formation of (CH₂)₂(NH₃)₂[U(PO₄)₂] (C2UP2) single crystals. C2UP2 undergoes a reversible phase transition from triclinic to monoclinic symmetry at about 230 °C. The structure of the two forms results from the stacking of inorganic layers (∞)¹[U(PO₄)₂]²⁻, and organic layers containing ethylene diammonium ions, the two layers being linked by hydrogen bonds. Single crystals of (CH₂)₂(NH₃)₂[PO₃OH] (C2HP) are formed by evaporation of the solution after filtering of C2UP2 single crystals. The structure of C2HP contains infinite (∞)¹[PO₃OH]²⁻ chains connected by (CH₂)₂(NH₃)₂²⁺ ions through hydrogen bonds.

Hydrothermal phase transformation of hematite to magnetite

“…A similar in situ reduction capability of EDA in neutral and basic solutions for the reduction of uranium from U 6+ to U 4+ has been reported by Jouffret et al [42]. In our study, the phase transition process should be similar.…”

Three New Ln‐Decavanadates Materials:Synthesis, Structure, and Photoluminescent Sensing for Detection of Zn2+ and Co2+

“…The peak at 604 cm –1 of 2 corresponds to Tb–O vibrations (Figure S8, Supporting Information). The peak at 602 cm –1 of 3 corresponds to Eu‐O vibrations (Figure S9, Supporting Information) …”

The actinides

“…46 The ''yl'' oxygens in the [UO 2 (OH) 4 ] 2À (aq) ion appear to exchange by an associative mechanism. 56 Cation-cation interactions have been a regular feature of recent MO 2 + chemistry (M = Np, U) and there is increasing study of the phenomenon in U(VI) compounds, such as [UO 2 (NO 2 TA) 2 (H 2 O)] 57 and in framework germanates. 56 Cation-cation interactions have been a regular feature of recent MO 2 + chemistry (M = Np, U) and there is increasing study of the phenomenon in U(VI) compounds, such as [UO 2 (NO 2 TA) 2 (H 2 O)] 57 and in framework germanates.…”