Structure and Bonding Investigation of Plutonium Peroxocarbonate Complexes Using Cerium Surrogates and Electronic Structure Modeling.

Herein, we report the synthesis and structural characterization of K8[(CO3)3Pu]2(µ-η2-η2-O2)2·12H2O. This is the second Pu-containing addition to the previously studied alkali-metal peroxocarbonate series M8[(CO3)3A]2(µ-η2-η2-O2)2·xH2O (M = alkali metal; A = Ce or Pu; x = 8, 10, 12, or 18), for which only the M = Na analogue has been previously reported when A = Pu. The previously reported crystal structure for Na8[(CO3)3Pu]2(µ-η2-η2-O2)2·12H2O is not isomorphous with its known Ce analogue. However, a new synthetic route to these M8[(CO3)3A]2(µ-η2-η2-O2)2·12H2O complexes, described below, has produced crystals of Na8[(CO3)3Ce]2(µ-η2-η2-O2)2·12H2O that are isomorphous with the previously reported Pu analogue. Via this synthetic method, the M = Na, K, Rb, and Cs salts of M8[(CO3)3Ce]2(µ-η2-η2-O2)2·xH2O have also been synthesized for a systematic structural comparison with each other and the available Pu analogues using single-crystal X-ray diffraction, Raman spectroscopy, and density functional theory calculations. The Ce salts, in particular, demonstrate subtle differences in the peroxide bond lengths, which correlate with Raman shifts for the peroxide Op-Op stretch (Op = O atoms of the peroxide bridges) with each of the cations studied: Na+ [1.492(3) Å/847 cm-1], Rb+ [1.471(1) Å/854 cm-1], Cs+ [1.474(1) Å/859 cm-1], and K+ [1.468(6) Å/870 cm-1]. The trends observed in the Op-Op bond distances appear to relate to supermolecular interactions between the neighboring cations.

Accelerated analyte uptake on single beads in microliter-scale batch separations using acoustic streaming: plutonium uptake by anion exchange for analysis by mass spectrometry.

The use of acoustic streaming as a noncontact mixing platform to accelerate mass-transport-limited diffusion processes in small-volume heterogeneous reactions has been investigated. Single-bead anion exchange of plutonium at nanomolar and subpicomolar concentrations in 20 microL liquid volumes was used to demonstrate the effect of acoustic mixing. Pu uptake rates on individual approximately 760 microm diameter AG 1 x 4 anion-exchange resin beads were determined using acoustic mixing and compared with Pu uptake rates achieved by static diffusion alone. An 82 MHz surface acoustic wave (SAW) device was placed in contact with the underside of a 384-well microplate containing flat-bottomed semiconical wells. Acoustic energy was coupled into the solution in the well, inducing acoustic streaming. Pu uptake rates were determined by the plutonium remaining in solution after specific elapsed time intervals using liquid scintillation counting (LSC) for nanomolar concentrations and thermal ionization mass spectrometry (TIMS) analysis for the subpicomolar concentration experiments. It was found that this small batch uptake reaction could be accelerated by a factor of about 5-fold or more, depending on the acoustic power applied.

First identification and thermodynamic characterization of the ternary U(VI) species, UO2(O2)(CO3)2(4-), in UO2-H2O2-K2CO3 solutions.

In alkaline carbonate solutions, hydrogen peroxide can selectively replace one of the carbonate ligands in UO2(CO3)3(4-) to form the ternary mixed U(VI) peroxo-carbonato species UO2(O2)(CO3)2(4-). Orange rectangular plates of K4[UO2(CO3)2(O2)].H2O were isolated and characterized by single crystal X-ray diffraction studies. Crystallographic data: monoclinic, space group P2(1)/ n, a = 6.9670(14) A, b = 9.2158(10) A, c = 18.052(4) A, Z = 4. Spectrophotometric titrations with H 2O 2 were performed in 0.5 M K 2CO 3, with UO2(O2)(CO3)2(4-) concentrations ranging from 0.1 to 0.55 mM. The molar absorptivities (M(-1) cm(-1)) for UO2(CO3)3(4-) and UO2(O2)(CO3)2(4-) were determined to be 23.3 +/- 0.3 at 448.5 nm and 1022.7 +/- 19.0 at 347.5 nm, respectively. Stoichiometric analyses coupled with spectroscopic comparisons between solution and solid state indicate that the stable solution species is UO2(O2)(CO3)2(4-), which has an apparent formation constant of log K' = 4.70 +/- 0.02 relative to the tris-carbonato complex.

Synthesis and structural characterization of a molecular plutonium(IV) compound constructed from dimeric building blocks.

Single crystals of Na(8)Pu(2)(O(2))(2)(CO(3))(6) x 12H(2)O, exhibiting bridging mu(2),eta(2)-O(2) ligands in unprecedented Pu(IV) dimeric units, were obtained at ambient temperature from an aqueous Pu(IV) peroxide carbonate solution.

Tetrapotassium dicarbonatodioxoperoxouranium(VI) 2.5-hydrate, K4[U(CO3)2O2(O2)].2.5H2O.

The title compound was obtained by reacting UO2 powder in 2 M K2CO3 with hydrogen peroxide. The compound contains individual [U(CO3)2O2(O2)]4- ions, which are linked via an extended network of K atoms and hydrogen bonding. The U atom is coordinated to two trans-axial O atoms and six O atoms in the equatorial plane, forming distorted hexagonal bipyramids. The carbonate ligands are bound to the U center in a bidentate manner, with U-O bond distances ranging from 2.438 (5) to 2.488 (5) A. The peroxo group forms a three-membered ring with the U atom, with U-O bond distances of 2.256 (6) and 2.240 (6) A. The U=O bond distances of 1.806 (5) and 1.817 (5) A, and an O-U-O angle of 175.3 (3) degrees are characteristic of the linear uranyl(VI) unit.