Trace Actinide Signatures of a Bulk Neptunium Sample.

In nuclear forensic analyses, measurements of actinide elements in a sample can assist with identifying interdicted or unknown materials. While these radiochemical signatures have been extensively investigated in uranium materials, less is known about bulk neptunium samples. This paper describes the measurement of trace actinide concentrations and isotopic profiles in a Np oxide sample.

Complexation of High-Valency Mid-Actinides by a Lipophilic Schiff Base Ligand: Synthesis, Structural Characterization, and Progress toward Selective Extraction.

Separation of U, Np, and Pu from used nuclear fuel (UNF) would result in lower long-term radiotoxicity, alleviating constraints on the storage and handling of the material. The complexity of UNF requires several industrial-scale processes with multiple waste streams. A one-step solution to the group removal of the elements, U-Pu, is desirable.

Plutonium coordination and redox chemistry with the CyMe-BTPhen polydentate N-donor extractant ligand.

Complexation of Pu(iv) with the actinide extractant CyMe-BTPhen (2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-1,10-phenanthroline) was followed by vis-NIR spectroscopy in acetonitrile solution. The solid-state structure of the crystallized product suggests that Pu(iv) is reduced to Pu(iii) upon complexation. Analysis by DFT modeling is consistent with metal-based rather than ligand-based reduction.

Neptunium and plutonium complexes with a sterically encumbered triamidoamine (TREN) scaffold.

The syntheses and characterisation of isostructural neptunium(iv) and plutonium(iv) complexes [An(IV)(TREN(TIPS))(Cl)] [An = Np, Pu; TREN(TIPS) = {N(CH2CH2NSiPr(i)3)3}(3-)] are reported, along with the demonstration that they are likely reduced to the corresponding neptunium(iii) and plutonium(iii) products [An(III)(TREN(TIPS))]; this chemistry provides new platforms from which to target a plethora of unprecedented molecular functionalities in transuranic chemistry and the neptunium(iv) molecule is the first structurally characterised neptunium(iv)-amide complex.

Coordination chemistry of 2,2'-biphenylenedithiophosphinate and diphenyldithiophosphinate with U, Np, and Pu.

New members of the dithiophosphinic acid family of potential actinide extractants were prepared: heterocyclic 2,2'-biphenylenedithiophosphinic acids of stoichiometry HS2P(R2C12H6) (R = H or (t)Bu). The time- and atom-efficient syntheses afforded multigram quantities of pure HS2P(R2C12H6) in reasonable yields (∼60%). These compounds differed from other diaryldithiophosphinic acid extractants in that the two aryl groups were connected to one another at the ortho positions to form a 5-membered dibenzophosphole ring.

A Linear trans-Bis(imido) Neptunium(V) Actinyl Analog: Np(V)(NDipp)2((t)Bu2bipy)2Cl (Dipp = 2,6-(i)Pr2C6H3).

The discovery that imido analogs of actinyl dioxo cations can be extended beyond uranium into the transuranic elements is presented. Synthesis of the Np(V) complex, Np(NDipp)2((t)Bu2bipy)2Cl (1), is achieved through treatment of a Np(IV) precursor with a bipyridine coligand and lithium-amide reagent. Complex 1 has been structurally characterized, analyzed by (1)H NMR and UV-vis-NIR spectroscopies, and the electronic structure evaluated by DFT calculations.

Unexpected Actinyl Cation-Directed Structural Variation in Neptunyl(VI) A-Type Tri-lacunary Heteropolyoxotungstate Complexes.

A-type tri-lacunary heteropolyoxotungstate anions (e.g., [PW9O34](9-), [AsW9O34](9-), [SiW9O34](10-), and [GeW9O34](10-)) are multidentate oxygen donor ligands that readily form sandwich complexes with actinyl cations ({UO2}(2+), {NpO2}(+), {NpO2}(2+), and {PuO2}(2+)) in near-neutral/slightly alkaline aqueous solutions.

Synthesis and characterization of NpCl4(DME)2 and PuCl4(DME)2 neutral transuranic An(IV) starting materials.

The 1,2-dimethoxyethane (DME) solvento adducts of Np(iv) and Pu(iv) tetrachloride have been prepared and isolated in good and moderate yields, respectively, along with single-crystal structural determinations. These neutral molecules are expected to provide alternative synthetic pathways in the pursuit of non-aqueous and organometallic complexes.

Plutonium(IV) complexation by diglycolamide ligands--coordination chemistry insight into TODGA-based actinide separations.

Complexation of Pu(IV) with TMDGA, TEDGA, and TODGA diglycolamide ligands was followed by vis-NIR spectroscopy. A crystal structure determination reveals that TMDGA forms a 1 : 3 homoleptic Pu(IV) complex with the nitrate anions forced into the outer coordination sphere.

[N(n-Bu)4]2[Pu(NO3)6] and [N(n-Bu)4]2[PuCl6]: starting materials to facilitate nonaqueous plutonium(IV) chemistry.

The reaction of plutonium(IV) in aqueous nitric acid with tetra-n-butylammonium nitrate leads to the immediate precipitation of [N(n-Bu)(4)](2)[Pu(NO(3))(6)] (1) in high yield. The analogous reaction in HCl with tetra-n-butylammonium chloride gives [N(n-Bu)(4)](2)[PuCl(6)] (2). Both 1 and 2 are soluble in a range of organic solvents and have been characterized by single-crystal X-ray diffraction, IR spectroscopy, and solid- and solution-phase vis-near-IR spectroscopy.

Bonding trends traversing the tetravalent actinide series: synthesis, structural, and computational analysis of An(IV)((Ar)acnac)4 complexes (An = Th, U, Np, Pu; (Ar)acnac = ArNC(Ph)CHC(Ph)O; Ar = 3,5-(t)Bu2C6H3).

A series of tetravalent An(IV) complexes with a bis-phenyl β-ketoiminate N,O donor ligand has been synthesized with the aim of identifying bonding trends and changes across the actinide series. The neutral molecules are homoleptic with the formula An((Ar)acnac)(4) (An = Th (1), U (2), Np (3), Pu (4); (Ar)acnac = ArNC(Ph)CHC(Ph)O; Ar = 3,5-(t)Bu(2)C(6)H(3)) and were synthesized through salt metathesis reactions with actinide chloride precursors. NMR and electronic absorption spectroscopy confirm the purity of all four new compounds and demonstrate stability in both solution and the solid state.

Synthesis and coordination chemistry of phosphine oxide decorated dibenzofuran platforms.

A four-step synthesis for 4,6-bis(diphenylphosphinoylmethyl)dibenzofuran (4) from dibenzofuran and a two-step synthesis for 4,6-bis(diphenylphosphinoyl)dibenzofuran (5) are reported along with coordination chemistry of 4 with In(III), La(III), Pr(III), Nd(III), Er(III), and Pu(IV) and of 5 with Er(III). Crystal structure determinations for the ligands, 4·CH(3)OH and 5, the 1:1 complexes [In(4)(NO(3))(3)], [Pr(4)(NO(3))(3)(CH(3)CN)]·0.5CH(3)CN, [Er(4)(NO(3))(3)(CH(3)CN)]·CH(3)CN, [Pu(4)Cl(4)]·THF and the 2:1 complex [Nd(4)(2)(NO(3))(2)](2)(NO(3))(2)·(H(2)O)·4(CH(3)OH) are described.

Synthesis and structure of (Ph4P)2MCl6 (M = Ti, Zr, Hf, Th, U, Np, Pu).

High-purity syntheses are reported for a series of first, second, and third row transition metal and actinide hexahalide compounds with equivalent, noncoordinating countercations: (Ph(4)P)(2)TiF(6) (1) and (Ph(4)P)(2)MCl(6) (M = Ti, Zr, Hf, Th, U, Np, Pu; 2-8). While a reaction between MCl(4) (M = Zr, Hf, U) and 2 equiv of Ph(4)PCl provided 3, 4, and 6, syntheses for 1, 2, 5, 7, and 8 required multistep procedures. For example, a cation exchange reaction with Ph(4)PCl and (NH(4))(2)TiF(6) produced 1, which was used in a subsequent anion exchange reaction with Me(3)SiCl to synthesize 2.

Stabilising pentavalent actinides--visible-near infrared and X-ray absorption spectroscopic studies of the utility of the [(Np3W4O15)(H2O)3(MW9O33)3]18- (M = Sb, Bi) structural type.

We report the interaction between B-type tri-lacunary heteropolyoxotungstate anions and actinyl(V) cations in aqueous solution, yielding a greater understanding of the stability of the O≡An≡O(1+) linear dioxo actinide moiety. Previously we reported that B-α-[BiW(9)O(33)](9-) and B-α-[SbW(9)O(33)](9-) will react with NpO(2)(1+) to yield [(Np(3)W(4)O(15))(H(2)O)(3)(MW(9)O(33))(3)](18-) (M = Bi, or Sb). Single crystal structural characterisation of salts of these complexes revealed a core in which three Np(V) atoms interact with a central W(VI) atom through bridging oxo groups.

Differences in actinide metal-ligand orbital interactions: comparison of U(IV) and Pu(IV) β-ketoiminate N,O donor complexes.

Syntheses and characterization of UCl(2)((Ar)acnac)(2), UI(2)((Ar)acnac)(2), and PuI(2)((Ar)acnac)(2) are reported ((Ar)acnac denotes a bis-phenyl β-ketoiminate ligand where Ar = 3,5-(t)Bu(2)C(6)H(3)). Structural analyses and computations show significant metal-ligand orbital interaction differences in U(IV) vs. Pu(IV) bonding.

Structural and spectroscopic characterization of plutonyl(VI) nitrate under acidic conditions.

The plutonyl(VI) dinitrate complex [PuO(2)(NO(3))(2)(H(2)O)(2)]·H(2)O (1) has been structurally characterized by single-crystal X-ray diffraction and spectroscopically characterized by solid-state vis-NIR and Raman spectroscopies. Aqueous solution spectroscopic studies indicate only weak plutonyl(VI) nitrate complexation, with the mononitrate complex dominating and negligible dinitrate formation, even in concentrated nitric acid.

The reaction chemistry of plutonyl(VI) chloride complexes with triphenyl phosphineoxide and triphenyl phosphinimine.

The reaction between Ph(3)PO dissolved in acetone and "PuO(2)Cl(2)" in dilute HCl resulted in the formation of [PuO(2)Cl(2)(Ph(3)PO)(2)]. Crystallographic characterization of the acetone solvate revealed the expected axial trans plutonyl dioxo, with trans Cl and Ph(3)PO in the equatorial plane. Spectroscopic analyses ((31)P NMR, (1)H NMR, and vis/nIR) indicate the presence of both cis and trans isomers in solution, with the trans isomer being more stable.

Probing the 5f electrons in a plutonyl(VI) cluster complex.

We report the structural, spectroscopic and preliminary magnetic characterisation of a tri-metallic plutonyl(VI) polyoxometalate complex, K(11)[K(3)(PuO(2))(3)(GeW(9)O(34))(2)] x 12 H(2)O.

Low-valent molecular plutonium halide complexes.

Treatment of plutonium metal with 1.5 equiv of bromine in tetrahydrofuran (thf) led to isolation of PuBr3(thf)4 (1), which is a new versatile synthon for exploration of non-aqueous Pu(III) chemistry. Adventitious water in the system resulted in structural characterization of the eight-coordinate complex [PuBr2(H2O)6][Br] (2).

Experimental and theoretical comparison of actinide and lanthanide bonding in M[N(EPR(2))(2)](3) complexes (M = U, Pu, La, Ce; E = S, Se, Te; R = Ph, iPr, H).

Treatment of M[N(SiMe3)2]3 (M = U, Pu (An); La, Ce (Ln)) with NH(EPPh2)2 and NH(EPiPr2)2 (E = S, Se), afforded the neutral complexes M[N(EPR2)2]3 (R = Ph, iPr). Tellurium donor complexes were synthesized by treatment of MI3(sol)4 (M = U, Pu; sol = py and M = La, Ce; sol = thf) with Na(tmeda)[N(TePiPr2)2]. The complexes have been structurally and spectroscopically characterized with concomitant computational modeling through density functional theory (DFT) calculations.

Structural characterization of Pu[N(SiMe(3))(2)](3), a synthetically useful nonaqueous plutonium(III) precursor.

A rare, and synthetically versatile, nonaqueous plutonium complex, Pu[N(SiMe3)2]3 (1), has been structurally characterized by single-crystal X-ray diffraction for the first time and reveals significantly shorter agostic interactions compared to the cerium(III) analogue, indicating possible covalency differences.

Plutonium(IV) reduction by the metal-reducing bacteria Geobacter metallireducens GS15 and Shewanella oneidensis MR1.

The bacterial reduction of actinides has been suggested as a possible remedial strategy for actinide-contaminated environments, and the bacterial reduction of Pu(VI/V) has the potential to produce highly insoluble Pu(IV) solid phases. However, the behavior of plutonium with regard to bacterial reduction is more complex than for other actinides because it is possible for Pu(IV) to be further reduced to Pu(III), which is relatively more soluble than Pu(IV). This work investigates the ability of the metal-reducing bacteria Geobacter metallireducens GS15 and Shewanella oneidensis MR1 to enzymatically reduce freshly precipitated amorphous Pu(IV) (OH)(4) [Pu(IV)(OH)(4(am))] and soluble Pu(IV)(EDTA).

An entry route into non-aqueous plutonyl coordination chemistry.

The Pu(VI) molecular complex, [PuO(2)Cl(2)(thf)(2)]2, is prepared by addition of a HCl/Et(2)O solution to a suspension of PuO(2)CO(3) in thf, yielding the first example of a precursor suitable for investigation of the non-aqueous chemistry of the plutonyl dioxo cation under inert atmospheric conditions.

Complexation of Pu(IV) with the natural siderophore desferrioxamine B and the redox properties of Pu(IV)(siderophore) complexes.

The bioavailability and mobility of Pu species can be profoundly affected by siderophores and other oxygen-rich organic ligands. Pu(IV)(siderophore) complexes are generally soluble and may constitute with other soluble organo-Pu(IV) complexes the main fraction of soluble Pu(IV) in the environment. In order to understand the impact of siderophores on the behavior of Pu species, it is important to characterize the formation and redox behavior of Pu(siderophore) complexes.

Iron(III) coordination properties of a pyoverdin siderophore produced by Pseudomonas putida ATCC 33015.

The iron complexation of a fluorescent green pyoverdin siderophore produced by the environmental bacterium Pseudomonas putida was characterized by solution thermodynamic methods. Pyoverdin binds iron through three bidentate chelate groups, a catecholate, a hydroxamate, and an alpha-hydroxycarboxylic acid. The deprotonation constants of the free pyoverdin and Fe(III)-pyoverdin complex were determined through a series of potentiometric and spectrophotometric experiments.