Gas-Phase Complexes of Americium and Lanthanides with a Bis-triazinyl Pyridine: Reactivity and Bonding of Archetypes for F-Element Separations.

Bis-triazinyl pyridines (BTPs) exhibit solution selectivity for trivalent americium over lanthanides (Ln), the origins of which remain uncertain. Here, electrospray ionization was used to generate gas-phase complexes [ML3]3+, where M = La, Lu, or Am and L is EtBTP 2,6-bis(5,6-diethyl-1,2,4-triazin-3-yl)-pyridine. Collision-induced dissociation (CID) of [ML3]3+ in the presence of H2O yielded a protonated ligand [L(H)]+ and hydroxide [ML2(OH)]2+ or hydrate [ML(L-H)(H2O)]2+, where (L-H)- is a deprotonated ligand. Although solution affinities indicate stronger binding of BTPs toward Am3+ versus Ln3+, the observed CID process is contrastingly more facile for M = Am versus Ln. To understand the disparity, density functional theory was employed to compute potential energy surfaces for two possible CID processes, for M = La and Am. In accordance with the CID results, both the rate determining transition state barrier and the net energy are lower for [AmL3]3+ versus [LaL3]3+ and for both product isomers, [ML2(OH)]2+ and [ML(L-H)(H2O)]2+. More facile removal of a ligand from [AmL3]3+ by CID does not necessarily contradict stronger Am3+-L binding, as inferred from solution behavior. In particular, the formation of new bonds in the products can distort kinetics and thermodynamics expected for simple bond cleavage reactions. In addition to correctly predicting the seemingly anomalous CID behavior, the computational results indicate greater participation of Am 5f versus La 4f orbitals in metal-ligand bonding

Understanding the Subsurface Reactive Transport of Transuranic Contaminants at DOE Sites

Our primary hypothesis is that actinides can interact with surfaces in fundamentally different ways than other metals, metalloids, and oxyanions and that this fundamental difference requires new approaches to studying and modeling transuranic sorption to minerals and geomedia. This project supports a key mission of the SBR program to develop sufficient scientific understanding such that DOE sites will be able to incorporate coupled physical, chemical, and biological processes into decision making for environmental management and long-term stewardship, while also supporting DOE’s commitment to education, training, and collaboration with DOE user facilities

A metal-organic framework material that functions as an enantioselective catalyst for olefin epoxidation,” Chem. Commun

A new microporous metal-organic framework compound featuring chiral (salen)Mn struts is highly effective as an asymmetric catalyst for olefin epoxidation, yielding enantiomeric excesses that rival those of the free molecular analogue. Framework confinement of the manganese salen entity enhances catalyst stability, imparts substrate size selectivity, and permits catalyst separation and reuse. Crystalline metal-organic framework (MOF) compounds, especially those exhibiting zeolite-like properties such as high internal surface area and microporosity, comprise a promising emerging class of functional materials. 1 Among the functions most often envisioned is chemical catalysis. 2 The notion is that MOF-based catalysts may be able to replicate some of the key features of zeolitic catalysts (e.g. single-site reactivity, pore-defined substrate size and shape selectivity, easy catalyst separation and recovery, and catalyst recyclability) while incorporating reactivity and properties unique to molecular catalysts. One important property of many molecular catalysts that has yet to be demonstrated with purely zeolitic catalysts is enantioselectivity. Herein, we report that a microporous MOF containing chiral (salen)Mn struts is highly effective as an asymmetric catalyst for olefin epoxidation. The observed enantiomeric excesses (ee) rival those of the free molecular catalyst. At the same time, framework confinement enhances catalyst stability, imparts substrate size selectivity, and permits catalyst separation and reuse. 6 Since MOFs based exclusively upon metal-pyridine bonding tend to collapse if evacuated, L was incorporated instead in a more robust pillared paddlewheel structure, 1, containing pairs of zinc ions together with biphenyldicarboxylate (bpdc) as the second ligand. Notwithstanding the interpenetration, solvent occupies 57% of the volume of 1 as determined by PLATON. Notably, the ligands L of the paired networks are parallel to each other with cyclohexyl and tert-butyl groups protruding along the [100] direction. As such, the channel in the crystallographic b direction is essentially blocked, leaving distorted-rectangular and rhombic channels in the c and a directions with dimensions of 6.2 6 15.7 Å an

Structural trends and bonding of the 5ƒ-elements (U-Am) with the oxoligand I03-.

The solid state chemistry of transuranium compounds has received considerably less attention than their uranium analogs owing to decreased availability and the highly specialized facilities needed to safely study long-lived {alpha}-emitters. However, understanding the behavior of the early transuranium elements is critical for assessing their environmental impact as long-term contributors to radioactive dose in nuclear waste repositories. Of particular interest is how these elements might react with fission product radionuclides such as 129I, or their derivatives. In fact, iodine can exist in solution in both oxidized and reduced forms, i .e. as I03 and F, and studies on the nature of129I in nuclear waste suggested the existence of iodate, 103.

Synthesis, structure, magnetism, and optical properties of theordered mixed-lanthanide sulfides gamma-LnLn'S3 (Ln=La, Ce; Ln'=Er, Tm,Yb)

{gamma}-LnLn{prime}S{sub 3} (Ln = La, Ce; Ln{prime} = Er, Tm, Yb) have been prepared as dark red to black single crystals by the reaction of the respective lanthanides with sulfur in a Sb{sub 2}S{sub 3} flux at 1000 C. This isotypic series of compounds adopts a layered structure that consists of the smaller lanthanides (Er, Tm, and Yb) bound by sulfide in six- and seven-coordinate environments that are connected together by the larger lanthanides (La and Ce) in eight- and nine-coordinate environments. The layers can be broken down into three distinct one-dimensional substructures containing three crystallographically unique Ln{prime} centers. The first of these is constructed from one-dimensional chains of edge-sharing [Ln{prime}S{sub 7}] monocapped trigonal prisms that are joined to equivalent chains via edge-sharing to yield ribbons. There are parallel chains of [Ln{prime}S{sub 6}] distorted octahedra that are linked to the first ribbons through corner-sharing. These latter units also share corners with a one-dimensional ribbon composed of parallel chains of [Ln{prime}S{sub 6}] polyhedra that edge-share both in the direction of chain propagation and with adjacent identical chains. Magnetic susceptibility measurements show Curie-Weiss behavior from 2 to 300 K with antiferromagnetic coupling, and no evidence for magnetic ordering. The {theta}{sub p} values range from -0.4 to -37.5 K, and spin-frustration may be indicated for the Yb-containing compounds. All compounds show magnetic moments substantially reduced from those calculated for the free ions. The optical band gaps for {gamma}-LaLn{prime}S{sub 3} (Ln{prime} = Er, Tm, Yb) are approximately 1.6 eV, whereas {gamma}-CeLn{prime}S{sub 3} (Ln{prime} = Er, Tm, Yb) are approximately 1.3 eV

Syntheses, Structure, Magnetism, and Optical Properties of Lutetium-based Interlanthanide Selenides

Ln{sub 3}LuSe{sub 6} (Ln = La, Ce), {beta}-LnLuSe{sub 3} (Ln = Pr, Nd), and Ln{sub x}Lu{sub 4-x}Se{sub 6} (Ln = Sm, Gd; x = 1.82, 1.87) have been synthesized using a Sb{sub 2}Se{sub 3} flux at 1000 C. Ln{sub 3}LuSe{sub 6} (Ln = La, Ce) adopt the U{sub 3}ScS{sub 6}-type three-dimensional structure, which is constructed from two-dimensional {infinity}{sup 2} [Ln{sub 3}Se{sub 6}]{sup 3-} slabs with the gaps between these slabs filled by octahedrally coordinated Lu{sup 3+} ions. The series of {beta}-LnLuSe{sub 3} (Ln = Pr, Nd) are isotypic with UFeS{sub 3}. Their structures include layers formed from LuSe6 octahedra that are separated by eight-coordinate larger Ln{sup 3+} ions in bicapped trigonal prismatic environments. Sm{sub 1.82}Lu{sub 2.18}Se{sub 6} and Gd{sub 1.87}Lu{sub 2.13}Se{sub 6} crystallize in the disordered F-Ln{sub 2}S{sub 3} type structure with the eight-coordinate bicapped trigonal prismatic Ln(1) ions residing in the one-dimensional channels formed by three different double chains via edge and corner sharing. These double chains are constructed from Ln(2)Se{sub 7} monocapped trigonal prisms, Ln(3)Se{sub 6} octahedra, and Ln(4)S{sub 6} octahedra, respectively. The magnetic susceptibilities of {beta}-PrLuSe{sub 3} and {beta}-NdLuSe{sub 3} follow the Curie-Weiss law. Sm{sub 1.82}Lu{sub 2.18}Se{sub 6} shows van Vleck paramagnetism. Magnetic measurements show that Gd{sub 1.87}Lu{sub 2.13}Se{sub 6} undergoes an antiferromagnetic transition around 4 K. Ce{sub 3}LuSe{sub 6} exhibits ferromagnetic ordering below 5 K. The optical band gaps for La{sub 3}LuSe{sub 6}, Ce{sub 3}LuSe{sub 6}, {beta}- PrLuSe{sub 3}, {beta}-NdLuSe{sub 3}, Sm{sub 1.82}Lu{sub 2.18}Se{sub 6}, and Gd{sub 1.87}Lu{sub 2.13}Se{sub 6} are 1.26, 1.10, 1.56, 1.61, 1.51, and 1.56 eV, respectively

Syntheses, Structure, Magnetism, and Optical Properties of the Partial Ordered Quaternary Interlanthanide Sulfides PrLnYb2S6 (Ln = Tb, Dy)

Dark red single crystals of PrLnYb{sub 2}S{sub 6} (Ln = Pr/Yb, Tb, Dy) have been synthesized through the reaction of elemental rare earth metals and S using a Sb{sub 2}S{sub 3} flux at 1000 C. These isotypic compounds adopt the F-Ln{sub 2}S3 three-dimensional open channel structure type. Eight-coordinate Pr{sup 3+} ions sit in the channels, which are constructed from three different edge-shared double chains running down the b axis, which contain Yb(1)S{sub 6} octahedra, Yb(2)S{sub 6}, octahedra and LnS{sub 7} monocapped trigonal prisms, respectively. Each double chain connects to four other neighbors by sharing vertices and edges. Considerable disordering in Ln positions was observed in single X-ray diffraction experiments only in the case of Pr/Yb. Least square refinements gave rise to the formulas of Pr{sub 1.34}Yb{sub 2.66}S{sub 6}, of PrTbYb{sub 2}S{sub 6}, and PrDyYb{sub 2}S{sub 6}, which are confirmed by the elemental analysis and magnetic susceptibility measurements. Pr1.34Yb2.66S{sub 6}, PrTbYb{sub 2}S{sub 6} and PrDyYb{sub 2}S{sub 6} are paramagnetic down to 2 K without any indications of long range magnetic ordering. The optical transitions for Pr{sub 1.34}Yb{sub 2.66}S{sub 6}, PrTbYb{sub 2}S{sub 6}, and PrDyYb{sub 2}S{sub 6} are at approximately 1.6 eV. Crystallographic data: Pr{sub 1.34}Yb{sub 2.66}S{sub 6}, monoclinic, space group P2{sub 1}/m, a = 10.960(2), b = 3.9501(8), c = 11.220(2) {angstrom}, {beta} = 108.545(3), V = 460.54(16), Z = 2; PrTbYb{sub 2}S{sub 6}, monoclinic, space group P2{sub 1}/m, a = 10.9496(10), b = 3.9429(4), c = 11.2206(10) {angstrom}, {beta} = 108.525(2), V = 459.33(7), Z = 2; PrDyYb{sub 2}S{sub 6}, monoclinic, space group P2{sub 1}/m, a = 10.9384(10), b = 3.9398(4), c = 11.2037(10) {angstrom}, {beta} = 108.612(2), V = 457.57(7), Z = 2

Syntheses, Structure, Magnetism, and Optical Properties of the Interlanthanide Sulfides delta-Ln2-xLuxS3 (Ln = Ce, Pr, Nd)

{delta}-Ln{sub 2-x}LuxS{sub 3} (Ln = Ce, Pr, Nd; x = 0.67-0.71) compounds have been synthesized through the reaction of elemental rare earth metals and S using Sb{sub 2}S{sub 3} flux at 1000 C. These compounds are isotypic with CeTmS{sub 3}, which has a complex three-dimensional structure. It includes four larger Ln{sup 3+} sites in eight- and nine-coordinate environments, two disordered seven-coordinate Ln{sup 3+}/Lu{sup 3+} positions, and two six-coordinate Lu{sup 3+} ions. The structure is constructed from one-dimensional chains of LnSn (n = 6-9) polyhedra that extend along the b axis. These polyhedra share faces or edges with two neighbors within the chains, while in the [ac] plane they share edges and corners with other chains. Least square refinements gave rise to the formulas of {delta}-Ce{sub 1.30}Lu{sub 0.70}S{sub 3}, {delta}-Pr{sub 1.29}Lu{sub 0.71}S{sub 3} and {delta}-Nd{sub 1.33}Lu{sub 0.67}S{sub 3}, which are consistent with the EDX analysis and magnetic susceptibility data. {delta}-Ln{sub 2-x}LuxS{sub 3} (Ln = Ce, Pr, Nd; x = 0.67-0.71) show no evidence of magnetic ordering down to 5 K. Optical properties measurements show that the band gaps for {delta}-Ce{sub 1.30}Lu{sub 0.70}S{sub 3}, {delta}-Pr{sub 1.29}Lu{sub 0.71}S{sub 3}, and {delta}-Nd{sub 1.33}Lu{sub 0.67}S{sub 3} are 1.25 eV, 1.38 eV, and 1.50 eV, respectively. Crystallographic data: {delta}-Ce{sub 1.30}Lu{sub 0.70}S{sub 3}, monoclinic, space group P2{sub 1}/m, a = 11.0186(7), b = 3.9796(3), c = 21.6562(15) {angstrom}, {beta} = 101.6860(10), V = 929.93(11), Z = 8; {delta}-Pr{sub 1.29}Lu{sub 0.71}S{sub 3}, monoclinic, space group P2{sub 1}/m, a = 10.9623(10), b = 3.9497(4), c = 21.5165(19) {angstrom}, {beta} = 101.579(2), V = 912.66(15), Z = 8; {delta}-Nd{sub 1.33}Lu{sub 0.67}S{sub 3}, monoclinic, space group P2{sub 1}/m, a = 10.9553(7), b = 3.9419(3), c = 21.4920(15) {angstrom}, {beta} = 101.5080(10), V = 909.47(11), Z = 8

A measurement of the tau mass and the first CPT test with tau leptons

We measure the mass of the tau lepton to be 1775.1+-1.6(stat)+-1.0(syst.) MeV using tau pairs from Z0 decays. To test CPT invariance we compare the masses of the positively and negatively charged tau leptons. The relative mass difference is found to be smaller than 3.0 10^-3 at the 90% confidence level.Comment: 10 pages, 4 figures, Submitted to Phys. Letts.