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A new binary compound, NpSe2, possesses metal-chalcogen and chalcogen-chalcogen interactions different from those reported for other metal dichalcogenides. Its structure is incommensurately modulated and features linear Se chains and valence-ambiguous Np cations.

A new binary compound, NpSe

Extended-coordination sphere interactions between dissolved metals and other ions, including electrolyte cations, are not known to perturb the electrochemical behavior of metal cations in water. Herein, we report the stabilization of higher-oxidation-state Np dioxocations in aqueous chloride solutions by hydrophobic tetra-n-alkylammonium (TAA+) cations—an effect not exerted by fully hydrated Li+ cations under similar conditions. Experimental and molecular dynamics simulation results indicate that TAA+ cations not only drive enhanced coordination of anionic Cl– ligands to NpV/VI but also associate with the resulting Np complexes via non-covalent interactions, which together decrease the electrode potential of the NpVI/NpV couple by up to 220 mV (ΔΔG = −22.2 kJ mol−1). Understanding the solvation-dependent interplay between electrolyte cations and metal–oxo species opens an avenue for controlling the formation and redox properties of metal complexes in solution. It also provides valuable mechanistic insights into actinide separation processes that widely use quaternary ammonium cations as extractants or in room temperature ionic liquids., The electrochemical behaviour of redox-active metal cations foremost depends on the metal centre’s inner-sphere coordination environment. Here the authors show that electrolyte cations unexpectedly stabilize higher-oxidation-state neptunium dioxocations in water through extended-coordination sphere interactions.

A neutral-framework thorium oxohydroxosulfate hydrate has been isolated from aqueous solution. This microporous structure, which self-assembles without a templating agent, is built from [Th6(OH)4O4(H2O)6]12+ hexamers and thorium(IV) monomers linked through bridging sulfates. Solution conditions were chosen to enable an active competition between sulfate and hydroxide for thorium coordination. Synthetic requirements are discussed for this rare example of a thorium(IV) polynuclear complex containing mixed oxo-, hydroxo-, and sulfato-bridging moieties.

The influence of countercations (An+) in directing the composition of monomeric metal–ligand (ML) complexes that precipitate from solution are often overlooked despite the wide usage of An+ in materials synthesis. Herein, we describe a correlation between the composition of ML complexes and A+ hydration enthalpies found for two related series of thorium (Th)–nitrate molecular compounds obtained by evaporating acidic aqueous Th–nitrate solutions in the presence of A+ counterions. Analyses of their chemical composition and solid-state structures demonstrate that A+ not only affects the overall solid-state packing of the Th–nitrato complexes but also influences the composition of the Th–nitrato monomeric anions themselves. Trends in composition and structure are found to correlate with A+ hydration enthalpies, such that the A+ with smaller hydration enthalpies associate with less hydrated and more anionic Th–nitrato complexes. This perspective, broader than the general assumption of size and charge as the do...

Colorless crystals of ThSiO4 (huttonite) (1) and (Ca0.5Na0.5)2NaThSi8O20 (2) have been synthesized by the solid-state reactions of ThO2, CaSiO3, and Na2WO4 at 1073 K. Green crystals of (Ca0.5Na0.5)2NaUSi8O20 (3) have been synthesized by the solid-state reactions of UO2, CaSiO3, and Na2WO4 at 1003 K. All three compounds have been characterized by single-crystal X-ray diffraction. Compound 1 adopts a monazite-type three-dimensional condensed structure, which is built from edge- and corner-shared ThO9 polyhedra and SiO4 tetrahedra. Compounds 2 and 3 are isostructural and they crystallize in a steacyite-type structure. The structure consists of discrete pseudocubic [Si8O20]8− polyanions, which are connected by An4+ cations into a three-dimensional framework. Each An atom coordinates to eight monodentate [Si8O20]8− moieties in a square antiprismatic geometry. Na+ and Ca2+ ions reside in the void within the framework. Raman spectra of 1, 2, and 3 were collected on single crystal samples. 1 displays more complex vibrational bands than thorite. Raman spectra of 2 and 3 are analogous with most of vibrational bands located at almost the same regions.

To explore the chemical analogy between thorium and heavier actinides in soft anionic environments, three new thorium phosphides (ThCuP2, β-ThCu2P2, and ThCu5P3) have been prepared through solid-state reactions using CuI as a reaction promoter. The structure of ThCuP2 can be described as a filled UTe2-type with both dimeric P24− and monomeric P3− anions, in which Th is coordinated by eight P atoms in a bicapped trigonal prismatic arrangement and Cu is tetrahedrally coordinated by four P atoms. β-ThCu2P2 contains only P3− anions and is isostructural with BaCu2S2. In this structure, Th is coordinated by seven P atoms in monocapped trigonal prismatic geometry and Cu is tetrahedrally coordinated by four P atoms. ThCu5P3 adopts the YCo5P3-type structure consisting of P3− anions. This structure contains Th atoms coordinated by six P atoms in a trigonal prismatic arrangement and Cu atoms that are either tetrahedrally coordinated by four P atoms or square pyramidally coordinated by five P atoms. Electric resistivity measurements and electronic structure calculations on β-ThCu2P2 indicate a metal. These new compounds may be charge-balanced and formulated as Th4+Cu+(P24−)1/2P3−, Th4+(Cu+)2(P3−)2, and Th4+(Cu+)5(P3−)3, respectively. The structural, bonding, and property relationships between these Th compounds and related actinide and rare-earth phases are discussed. Titled compounds display more diverse ion–ion interactions and different electronic structures from those in UCuP2 and UCu2P2 that were synthesized under similar experimental conditions, suggesting divergence of thorium-phosphide chemistry from uranium-phosphide chemistry.

A neutral-framework thorium oxohydroxosulfate hydrate has been isolated from aqueous solution. This microporous structure, which self-assembles without a templating agent, is built from [Th6(OH)4O4(H2O)6]12+ hexamers and thorium(IV) monomers linked through bridging sulfates. Solution conditions were chosen to enable an active competition between sulfate and hydroxide for thorium coordination. Synthetic requirements are discussed for this rare example of a thorium(IV) polynuclear complex containing mixed oxo-, hydroxo-, and sulfato-bridging moieties.

Single crystals of Np2Se5 have been prepared through the reactions of Np and Se at 1223 K in an Sb2Se3 flux. The structure of Np2Se5, which has been characterized by single-crystal X-ray diffraction methods, crystallizes in the tetragonal space group P42/nmc. The crystallographic unit cell includes one unique Np and two Se positions. Se(1) atoms form one-dimensional infinite chains along the a and b axes with alternating intermediate Se-Se distances of 2.6489 (8) and 2.7999 (8) Å, whereas Se(2) is a discrete Se(2-) anion. Each Np is coordinated to 10 Se atoms and every NpSe10 polyhedron shares faces, edges, or vertices with 14 other identical metal polyhedra to form a complex three-dimensional structure. Np LIII-edge X-ray Absorption Near Edge Structure (XANES) measurements show a clear shift in edge position to higher energies for Np2Se5 compared to Np3Se5 (Np(3+)2Np(4+)Se(2-)5). Magnetic susceptibility measurements indicate that Np2Se5 undergoes a ferromagnetic-type ordering below 18(1) K. Above the transition temperature, Np2Se5 behaves as a paramagnet with an effective moment of 1.98(5) μB/Np, given by a best fit of susceptibilities to a modified Curie-Weiss law over the temperature range 50-320 K.

A neutral-framework thorium oxohydroxosulfate hydrate has been isolated from aqueous solution. This microporous structure, which self-assembles without a templating agent, is built from [Th

Cation-cation interactions (CCIs) are an essential feature of actinyl chemistry, particularly neptunyl(V). To better understand the formation mechanisms of CCIs, the crystallization process of Np(V) CCI compounds has been explored during the evaporation of acidic Np(V) stock solutions using X-ray diffraction and both ex situ and in situ Raman spectroscopy. At least four Np solid products have been isolated from evaporation of the same Np(V) acidic solution. In situ evaporation using a continuous wave laser (532 nm) as a local heat source produced similar solid products to ex situ experiments with matching Raman signatures. The formation of these products is highly dependent on the evaporation conditions. Slower evaporation appears to favor the formation of a new neptunyl(V) compound, (NpO2)Cl(H2O)2 (1), over other solid products. The structure of 1 features a three-dimensional network of NpO2(+) cations, where neighboring Np(V) ions are only connected to each other through CCIs in a square arrangement. The O═Np═O stretching region shows similar Raman bands in both the solids and solution suggesting that CCIs between Np(V) cations exist prior to crystallization. These results provide new insight into the formation mechanism of Np(V) CCI compounds from solutions.

Black single crystals of A(6)Cu(12)U(2)S(15) (A = K, Rb, Cs) have been synthesized by the reactive flux method. These isostructural compounds crystallize in the cubic space group Ia 3d at room temperature. The structure comprises a three-dimensional framework built from US(6) octahedra and CuS(3) trigonal planar units with A cations residing in the cavities. There are no S-S bonds in the structure. To elucidate the oxidation state of U in these compounds, various physical property measurements and characterization methods were carried out. Temperature-dependent electrical resistivity measurement on a single crystal of K(6)Cu(12)U(2)S(15) showed it to be a semiconductor. These three A(6)Cu(12)U(2)S(15) (A = K, Rb, Cs) compounds all exhibit small effective magnetic moments, < 0.58 μ(B)/U and band gaps of about 0.55(2) eV in their optical absorption spectra. From X-ray absorption near edge spectroscopy (XANES), the absorption edge of A(6)Cu(12)U(2)S(15) is very close to that of UO(3). Electronic band structure calculations at the density functional theory (DFT) level indicate a strong degree of covalency between U and S atoms, but theory was not conclusive about the formal oxidation state of U. All experimental data suggest that the A(6)Cu(12)U(2)S(15) family is best described as an intermediate U(5+)/U(6+) sulfide system of (A(+))(6)(Cu(+))(12)(U(5+))(2)(S(2-))(13)(S(-))(2) and (A(+))(6)(Cu(+))(12)(U(6+))(2)(S(2-))(15).

Dark green crystals of (NpO2)3(OH)(SeO3)(H2O)2·H2O (1) have been prepared by a hydrothermal reaction of neptunyl(V) and Na2SeO4 in an aqueous solution at 150 °C, while green plates of Na(NpO2)(SeO3...

Green crystals of (NpO(2))(2)(SeO(4))(H(2)O)(4), (NpO(2))(2)(SeO(4))(H(2)O)(2), and (NpO(2))(2)(SeO(4))(H(2)O) have been prepared by hydrothermal methods. The structures of these compounds have been characterized by single-crystal X-ray diffraction. (NpO(2))(2)(SeO(4))(H(2)O)(4), isostructural with (NpO(2))(2)(SO(4))(H(2)O)(4), is constructed from layers comprised of corner-sharing neptunyl(V) pentagonal bipyramids and selenate tetrahedra that are further linked by hydrogen bonding with water molecules. Each NpO(2)(+) cation binds to four other NpO(2)(+) units through cation-cation interactions (CCIs) to form a distorted "cationic square net" decorated by SeO(4)(2-) tetrahedra above and below the layer. Each selenate anion is bound to two neptunyl(V) cations through monodentate linkages. (NpO(2))(2)(SeO(4))(H(2)O)(2) is isostructural with the corresponding sulfate analogue as well. It consists of puckered layers of neptunyl(V) pentagonal bipyramids that are further connected by selenate tetrahedra to form a three-dimensional framework. The CCI pattern in the neptunyl layers of dihydrate is very similar to that of tetrahydrate; however, each SeO(4)(2-) tetrahedron is bound to four NpO(2)(+) cations in a mondentate manner. (NpO(2))(2)(SeO(4))(H(2)O) crystallizes in the monoclinic space group P2(1)/c, which differs from the (NpO(2))(2)(SO(4))(H(2)O) orthorhombic structure due to the slightly different connectivities between NpO(2)(+) cations and anionic ligands. The structure of (NpO(2))(2)(SeO(4))(H(2)O) adopts a three-dimensional network of distort neptunyl(V) pentagonal bipyramids decorated by selenate tetrahedra. Each NpO(2)(+) cation connects to four other NpO(2)(+) units through CCIs and also shares an equatorial coordinating oxygen atom with one of the other units in addition to the CC bond to form a dimer. Each SeO(4)(2-) tetrahedron is bound to five NpO(2)(+) cations in a monodentate manner. Magnetic measurements obtained from the powdered tetrahydrate are consistent with a ferromagnetic ordering of the neptunyl(V) spins at 8(1) K, with an average low temperature saturation moment of 1.98(8) μ(B) per Np. Well above the ordering temperature, the susceptibility follows Curie-Weiss behavior, with an average effective moment of 3.4(2) μ(B) per Np and a Weiss constant of 14(4) K. Correlations between lattice dimensionality and magnetic behavior are discussed.

Ln2YbCuQ5 (Ln = La, Ce, Pr, Nd, Sm; Q = S, Se) have been prepared by direct reaction of the elements in Sb2Q3 (Q = S, Se) fluxes at 900 °C. All compounds have been characterized by single-crystal X-ray diffraction methods and are isotypic. The structure of Ln2YbCuQ5 consists of one-dimensional ∞1[YbCuQ5]6− ribbons extending along the b-axis that are connected by larger Ln3+ ions. Each ribbon is constructed from two single chains of [YbQ6] octahedra with one double chain of [CuQ5] trigonal bipyramids in the middle. All three chains connect with each other via edge-sharing. There are two crystallographically unique Ln atoms, one octahedral Yb site, and two disordered Cu positions inside of distorted Q5 trigonal bipyramids. Both Ln atoms are surrounded by eight Q atoms in bicapped trigonal prisms. The magnetic properties of Ln2YbCuQ5 have been characterized using magnetic susceptibility and heat capacity measurements, while their optical properties have been explored using UV−vis−NIR diffuse reflectance spec...

The compounds UOS, UOSe, NpOS, and NpOSe have been synthesized and their structures determined by means of single-crystal X-ray diffraction methods. The results provide more detailed crystallographic information, including more precise interatomic distances, than earlier determinations from powder diffraction data. These isostructural compounds adopt the PbFCl structure type. Each An atom is surrounded by four O and five Q atoms in a distorted monocapped square-antiprismatic arrangement.

The five quaternary neptunium compounds KCuNpS3, RbCuNpS3, CsCuNpS3, KAgNpS3, and CsAgNpS3 (AMNpS3) have been synthesized by the reaction of Np, Cu or Ag, S, and K2S or Rb2S3 or Cs2S3 at 793 K (Rb) or 873 K. These isostructural compounds crystallize as black rectangular plates in the KCuZrS3 structure type in space group Cmcm of the orthorhombic system. The structure comprises MS4 (M = Cu or Ag) tetrahedra and NpS6 octahedra that edge share to form infinity 2[MNpS3-] layers. These layers are separated by the alkali-metal cations. The Np-S bond lengths vary from 2.681(2) to 2.754(1) A. When compared to the corresponding isostructural Th and U compounds these bond distances obey the expected actinide contraction. As the structure contains no S-S bonds, formal oxidation states of +1/+1/+4/-2 may be assigned to A/M/Np/S, respectively. From these results a value of 2.57 for the bond-valence parameter r0 for Np(4+)-S(2-) has been derived and applied to the estimation of the formal oxidation states of Np in the binary NpxSy compounds whose structures are known.

Dark-red square plates of the previously reported compounds "(UO)(2)LnS(3)" (Ln = Yb, Y) have been synthesized by solid-state reactions of UOS and YbS or Y(2)S(3) with Sb(2)S(3) as a flux at 1273 K. The structure of these isotypic compounds was reinvestigated by single-crystal X-ray diffraction methods and an inductively coupled plasma experiment. The actual formula of "(UO)(2)LnS(3)" (Ln = Yb, Y) is (U(0.5)Ln(0.5)O)(2)LnS(3), that is, ULn(2)O(2)S(3), which can be charge-balanced with U(4+) and Ln(3+). The layered structure comprises (U/Ln)O(4)S(4) square antiprisms alternating with LnS(6) octahedra. U and Ln1 atoms disorder on the eight-coordinate metal position, but Ln2 atoms occupy the six-coordinate metal position exclusively. UYb(2)O(2)S(3) is a modified Curie-Weiss paramagnet between 293 and 32 K, below which part of the paramagnetic moments go through a possible ferromagnetic transition. The band gaps of ULn(2)O(2)S(3) (Ln = Yb, Y) are around 2 eV.

Red needles of UY{sub 4}O{sub 3}S{sub 5} have been synthesized by the solid-state reaction at 1273 K of UOS and Y{sub 2}S{sub 3} with Sb{sub 2}S{sub 3} as a flux. UY{sub 4}O{sub 3}S{sub 5} adopts a three-dimensional structure that contains five crystallographically unique heavy-atom positions. U and Y atoms disorder on one eight-coordinate metal position bonded to four O atoms and four S atoms and two seven-coordinate metal positions bonded to three O atoms and four S atoms. Another eight-coordinate metal position with two O and six S atoms and one six-coordinate metal position with six S atoms are exclusively occupied by Y atoms. UY{sub 4}O{sub 3}S{sub 5} is a modified Curie-Weiss paramagnet between 1.8 and 300 K. Its effective magnetic moment is estimated to be 3.3(2) mu{sub B}. UY{sub 4}O{sub 3}S{sub 5} has a band gap of 1.95 eV. The electrical resistivity along the [010] direction of a single crystal shows Arrhenius-type thermal activation with an activation energy of 0.2 eV. - Graphical abstract: View of the crystal structure of UY4O3S5.

Three gadolinium scandium chalcogenides have been synthesized using Sb2Q3 (Q=S, Se) fluxes at 975 °C. Gd3.04Sc0.96S6, GdScS3, and Gd1.05Sc0.95Se3 are crystallized in U3ScS6 type, GdFeO3 type, and UFeS3 type structures, respectively. The magnetic susceptibilities for these compounds follow the Curie–Weiss law above their transition temperatures. The effective magnetic moments are close to calculated values for free Gd3+ ions. The Weiss constants for Gd3.04Sc0.96S6, GdScS3, and Gd1.05Sc0.95Se3 are determined to be −3.3(1), −4.5(4), and 1.5(1) K, respectively. Gd3.04Sc0.96S6 orders antiferromagnetically below 9 K. GdScS3 exhibits an antiferromagnetic ordering below 3 K with a weak ferromagnetism. Gd1.05Sc0.95Se3 undergoes a ferromagnetic transition around 5 K. The optical band gaps for Gd3.04Sc0.96S6, GdScS3, and Gd1.05Sc0.95Se3 are 1.5, 2.1, and 1.2 eV, respectively.

EuLn2Q4 (Ln=Tb–Lu; Q=S, Se) has been synthesized using Sb2Q3 (Q=S, Se) fluxes at 1000 °C. These compounds crystallize in a CaFe2O4-type three-dimensional channel structure that is built from edge-shared double rutile chains of [LnQ6] octahedra running down the b-axis. Each double chain is connected at the vertices to four other double chains to form open channels where bicapped trigonal prismatic Eu2+ ions reside. All of these compounds show antiferromagnetic ordering with Neel temperatures, TN∼3–4 K. The optical band gaps for EuTb2Se4, EuDy2Se4, EuHo2Se4, EuEr2Se4, EuTm2Se4, EuYb2Se4 EuLu2Se4, and EuYb2S4 are found to be 2.0, 1.8, 1.8, 1.7, 1.8, 1.3, 1.7, and 1.6 eV, respectively.

{sup 151}Eu and {sup 121}Sb Moessbauer spectroscopy of EuSbSe{sub 3} and EuBiSe{sub 3} were measured at different temperatures. The presence of divalent europium and trivalent antimony were confirmed. The largely negative values of the isomer shift in {sup 151}Eu spectrum show highly ionic bonding within these two compounds. Both of them show magnetic hyperfine field splitting at 4.2 K, which indicates a change in the orientation of the EFG principal axis with respect to the magnetic hyperfine field direction. EuSbSe{sub 3} has slightly smaller electron density at the antimony nuclei, compared to Sb{sub 2}Se{sub 3.} - Graphical abstract: Experimental and simulated {sup 121}Sb Moessbauer spectrum of EuSbSe{sub 3} at 77 K.

Dark red single crystals of PrLnYb{sub 2}S{sub 6} (Ln=Pr/Yb, Tb, Dy) have been synthesized through the reactions of elemental rare earth metals and S using a Sb{sub 2}S{sub 3} flux at 1000 deg. C. These isotypic compounds adopt the F-Ln{sub 2}S{sub 3} three-dimensional open-channel structure type. Eight-coordinate Pr{sup 3+} ions sit in the channels that are constructed from three different edge-shared double chains running down the b-axis that contain Yb(1)S{sub 6} octahedra, Yb(2)S{sub 6} octahedra, and LnS{sub 7} monocapped trigonal prisms. 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-squares 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. 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 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 are listed as an example for PrTbYb{sub 2}S{sub 6}: monoclinic, spacemore » group P2{sub 1}/m, a=10.9496(10) A, b=3.9429(4) A, c=11.2206(10) A, {beta}=108.525(2){sup o}, V=459.33(7) A{sup 3}, Z=2. - Graphical abstract: An illustration of the three-dimensional structure of PrTbYb{sub 2}S{sub 6} viewed along the b-axis.« less

δ-Ln2−xLuxS3 (Ln=Ce, Pr, Nd; x=0.67–0.71) compounds have been synthesized through the reaction of elemental rare-earth metals and S using a Sb2S3 flux at 1000 °C. These compounds are isotypic with CeTmS3, which has a complex three-dimensional structure. It includes four larger Ln3+ sites in eight- and nine-coordinate environments, two disordered seven-coordinate Ln3+/Lu3+ positions, and two six-coordinate Lu3+ 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 δ-Ce1.30Lu0.70S3, δ-Pr1.29Lu0.71S3 and δ-Nd1.33Lu0.67S3, which are consistent with the EDX analysis and magnetic susceptibility data. δ-Ln2−xLuxS3 (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 δ-Ce1.30Lu0.70S3, δ-Pr1.29Lu0.71S3, and δ-Nd1.33Lu0.67S3 are 1.25, 1.38, and 1.50 eV, respectively. Crystallographic data: δ-Ce1.30Lu0.70S3, monoclinic, space group P21/m, a=11.0186(7), b=3.9796(3), c=21.6562(15) A, β=101.6860(10), V=929.93(11), Z=8; δ-Pr1.29Lu0.71S3, monoclinic, space group P21/m, a=10.9623(10), b=3.9497(4), c=21.5165(19) A, β=101.579(2), V=912.66(15), Z=8; δ-Nd1.33Lu0.67S3, monoclinic, space group P21/m, a=10.9553(7), b=3.9419(3), c=21.4920(15) A, β=101.5080(10), V=909.47(11), Z=8.

γ-LnLn‘S3 (Ln = La, Ce; Ln‘ = Er, Tm, Yb) have been prepared as dark red to black single crystals by the reaction of the respective lanthanides with sulfur in a Sb2S3 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‘ centers. The first of these is constructed from one-dimensional chains of edge-sharing [Ln‘S7] monocapped trigonal prisms that are joined to equivalent chains via edge sharing to yield ribbons. There are parallel chains of [Ln‘S6] 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‘S6] ...

Colorless crystals of ThSiO4 (I) and (Ca0.5Na0.5) 2NaThSi8O20 (II) are prepared by solid state reactions of ThO2, CaSiO3, and Na2WO4 (evacuated silica ampoules, 1073 K, 140 h).

EuPnSe3 (Pn=Sb, Bi) have been synthesized through the reaction of Eu with Pn2Se3 (Pn=Sb, Bi) and Se at 850–900 °C. These compounds are isotypic with SrPnSe3 (Pn=Sb, Bi) and consist of square pyramidal PnSe5 units and distorted PnSe6 octahedra that form hollow columns that extend along the c-axis. These columns are separated by Eu2+ cations that occur as nine-coordinate tricapped trigonal prisms. There are also additional V-shaped triselenide Se32− anions between the columns that bind the Eu2+ cations. The Se⋯Se contacts (in EuSbSe3) in these units are 2.4584(11) and 2.4359(11) A, which are consistent with Se–Se single bonds. The overall structure is chiral. Bond-valence sum calculations indicate that these compounds contain Eu2+. Magnetic susceptibility measurements provide values of 7.66 μB/Eu for EuSbSe3 and 7.64 μB/Eu for EuBiSe3, which are close to the expected free-ion moment for Eu2+. These compounds follow essentially Curie behavior from 300 to 5 K, and undergo an apparently antiferromagnetic transition below 5 K. Crystallographic data: EuSbSe3, orthorhombic, space group P212121, a = 32.936 ( 2 ) A , b = 15.406 ( 1 ) A , c = 4.2622 ( 3 ) A , V = 2162.7 ( 2 ) A 3 , Z = 16 , R ( F ) = 2.63 % for 183 parameters and 5095 reflections with I > 2 σ ( I ) ; EuBiSe3, orthorhombic, space group P212121, a = 33.307 ( 2 ) A , b = 15.5804 ( 9 ) A , c = 4.2274 ( 2 ) A , V = 2193.7 ( 2 ) A 3 , Z = 16 , R ( F ) = 2.68 % for 183 parameters and 4895 reflections with I > 2 σ ( I ) .

NaxNpIV(NpVO2)6 (OH)1+xCl9(H2O)8-x (0 < x ≤ 1) is synthesized by evaporation of a neptunium(V) acidic (HCl) stock solution over several months to complete dryness.

A new mixed-valent neptunium(IV/V) compound has been synthesized by evaporation of a neptunium(V) acidic solution. The structure of the compound features cation-cation-bound six-membered neptunyl(V) rings. These rings are further connected by Np(IV) ions through cation-cation interactions (CCIs) into a three-dimensional neptunium cationic open framework. This example illustrates the possibility of isolating neptunyl(V) CCI oligomers in inorganic systems using other cations to compete with Np(V) in bonding with the neptunyl oxygen.

Green crystals of Na(NpO(2))(SeO(4))(H(2)O) (1), Na(3)(NpO(2))(SeO(4))(2)(H(2)O) (2), and Na(3)(NpO(2))(SeO(4))(2)(H(2)O)(2) (3) have been prepared by a hydrothermal method for 1 or evaporation from aqueous solutions for 2 and 3. The structures of these compounds have been characterized by single-crystal X-ray diffraction. Compound 1 is isostructural with Na(NpO(2))(SO(4))(H(2)O) (4). The structure of 1 consists of ribbons of neptunyl(V) pentagonal bipyramids, which are decorated and further connected by selenate tetrahedra to form a three-dimensional framework. The resulting open channels are filled by Na(+) cations and H(2)O molecules. Within the ribbon, each neptunyl polyhedron shares corners with each other solely through cation-cation interactions (CCIs). The structure of 2 adopts one-dimensional [(NpO(2))(SeO(4))(2)(H(2)O)](3-) chains connected by Na(+) cations. Each NpO(2)(+) cation is coordinated by four monodentate SeO(4)(2-) anions and one H(2)O molecule to form a pentagonal bipyramid. The structure of 3 is constructed by one-dimensional [(NpO(2))(SeO(4))(2)](3-) chains separated by Na(+) cations and H(2)O molecules. These chains have two configurations resulting in two disordered orientations of the Se(2)O(4)(2-) tetrahedra. Each NpO(2)(+) cation is coordinated by one bidentate Se(1)O(4)(2-) and three monodentate Se(2)O(4)(2-) anions to form a pentagonal bipyramid. Raman spectra of 1, 2, and 4 were collected on powder samples. For 1 and 4, the neptunyl symmetric stretch modes (670, 676, 730, and 739 cm(-1)) shift significantly toward lower frequencies compared to that in 2 (773 cm(-1)), and there are several asymmetric neptunyl stretch bands in the region of 760-820 cm(-1). Magnetic measurements obtained from crushed crystals of 1 are consistent with a ferromagnetic ordering of the neptunyl(V) spins at 6.5(2) K, with an average low temperature saturation moment of 2.2(1) μ(B) per Np. Well above the ordering temperature, the susceptibility follows Curie-Weiss behavior, with an average effective moment of 3.65(10) μ(B) per Np and a Weiss constant of 14(1) K. Correlations between lattice dimensionality and magnetic behavior are discussed.

Black crystals of (III), (IV), (VI), and (VIII) are synthesized by solid state reactions and their structures are determined by single crystal XRD.

Black crystals of Np(PS(4)), Np(P(2)S(6))(2), K(11)Np(7)(PS(4))(13), and Rb(11)Np(7)(PS(4))(13) have been synthesized by the reactions of Np, P(2)S(5), and S at 1173 and 973 K; Np, K(2)S, P, and S at 773 K; and Np, Rb(2)S(3), P, and S at 823 K, respectively. The structures of these compounds have been characterized by single-crystal X-ray diffraction methods. Np(PS(4)) adopts a three-dimensional structure with Np atoms coordinated to eight S atoms from four bidentate PS(4)(3-) ligands in a distorted square antiprismatic arrangement. Np(PS(4)) is isostructural to Ln(PS(4)) (Ln = La-Nd, Sm, Gd-Er). The structure of Np(P(2)S(6))(2) is constructed from three interpenetrating diamond-type frameworks with Np atoms coordinated to eight S atoms from four bidentate P(2)S(6)(2-) ligands in a distorted square antiprismatic geometry. The centrosymmetric P(2)S(6)(2-) anion comprises two PS(2) groups connected by two bridging S centers. Np(P(2)S(6))(2) is isostructural to U(P(2)S(6))(2). A(11)Np(7)(PS(4))(13) (A = K, Rb) adopts a three-dimensional channel structure built from interlocking [Np(7)(PS(4))(13)](11-)-screw helices with A cations residing in the channels. The structure of A(11)Np(7)(PS(4))(13) includes four crystallographically independent Np atoms. Three are connected to eight S atoms in bicapped trigonal prisms. The other Np atom is connected to nine S atoms in a tricapped trigonal prism. A(11)Np(7)(PS(4))(13) is isostructural to A(11)U(7)(PS(4))(13). From Np-S bond distances and charge-balance, we infer that Np is trivalent in Np(PS(4)) and tetravalent in Np(P(2)S(6))(2) and A(11)Np(7)(PS(4))(13). Np exhibits a behavior intermediate between U and Pu in its thiophosphate chemistry.

Green crystals of (NpO2)2(SeO4)(H2O)4 (I), (NpO2)2(SeO4)(H2O)2 (II), and (NpO2)2(SeO4)(H2O) (III) are hydrothermally synthesized from mixtures of Na2SeO4 in 2 M aq.

Dark green crystals of (NpO(2))(3)(OH)(SeO(3))(H(2)O)(2)·H(2)O (1) have been prepared by a hydrothermal reaction of neptunyl(V) and Na(2)SeO(4) in an aqueous solution at 150 °C, while green plates of Na(NpO(2))(SeO(3))(H(2)O) (2) have been synthesized by evaporation of a solution of neptunyl(V), H(2)SeO(4), and NaOH at room temperature. Both compounds have been characterized by single-crystal X-ray diffraction. The structure of compound contains three crystallographically unique Np atoms that are bonded to two O atoms to form a nearly linear O═Np═O NpO(2)(+) cation. Neighboring Np(5+) ions connect to each other through a bridging oxo ion from the neptunyl unit, a configuration known as cation-cation interactions (CCIs), to build a complex three-dimensional network. More specifically, each Np(1)O(2)(+), Np(2)O(2)(+), and Np(3)O(2)(+) cation is involved in three, five, and four CCIs with other units, respectively. The framework of neptunyl(V) pentagonal bipyramids is decorated by selenite trigonal pyramids with one-dimensional open channels where uncoordinated waters are trapped via hydrogen bonding interactions. Compound adopts uranophane-type [(NpO(2))(SeO(3))](-) layers, which are separated by Na(+) cations and water molecules. Within each layer, neptunyl(V) pentagonal bipyramids share equatorial edges with each other to form a single chain that is further connected by both monodentate and bidentate selenite trigonal pyramids. Crystallographic data: compound, monoclinic, P2(1)/c, Z = 4, a = 6.6363(8) Å, b = 15.440(2) Å, c = 11.583(1) Å, β = 103.549(1)°, V = 1153.8(2) Å(3), R(F) = 0.0387 for I2σ(I); compound (2), monoclinic, C2/m, Z = 4, a = 14.874(4) Å, b = 7.271(2) Å, c = 6.758(2) Å, β = 112.005(4)°, V = 677.7(3) Å(3), R(F) = 0.0477 for I2σ(I).

Colorless crystals of CsTh(MoO4)2Cl (I) and Na4Th(WO4)4 (II) are synthesized by solid state reactions of either ThO2, MoO3, and excess CsCl, or ThCl4 and Na2WO4 (silica ampules, 993 K, 120 h).

The black title compounds are synthesized by reactions of the elements in Sb2Q3 (Q: S, Se) fluxes at 900 °C for 7 d and characterized by single crystal XRD, UV/VIS/NIR diffuse reflectance spectroscopy, and magnetic susceptibility measurements.

Black prisms of the title compounds are prepared by reactions of stoichiometric mixtures of Np and S or Se in a CsCl flux at 1173 K for 4 d.

Black prisms of the title compounds are prepared by reactions of the elements using CsCl as a flux (1173 K, 4 d).

Black prisms of Np(3)Q(5) (Q = S, Se) have been synthesized by the stoichiometric reactions between Np and Q at 1173 K in a CsCl flux. The structures of these compounds were characterized by single-crystal X-ray diffraction methods. The Np(3)Q(5) compounds are isostructural with U(3)Q(5). The structure of Np(3)Q(5) is constructed from layers of Np(1)Q(8) distorted bicapped trigonal prisms that share faces with each other on bc planes. Each Np(1)Q(8) layer further shares Q(2) edges with two adjacent identical neighbors to form a three-dimensional framework. The space inside each channel within this framework is filled by one single edge-sharing Np(2)Q(7) distorted 7-octahedron chain running along the b axis. Magnetic susceptibility measurements show that Np(3)S(5) and Np(3)Se(5) have antiferromagnetic orderings at 35(1) and 36(1) K, respectively. Above the magnetic ordering temperatures, both Np(3)S(5) and Np(3)Se(5) behave as typical Curie-Weiss paramagnets. The effective moments obtained from the fit of the magnetic data to a modified Curie-Weiss law over the temperature range 70 to 300 K are 2.7(2) μ(B) (Np(3)S(5)) and 2.9(2) μ(B) (Np(3)Se(5)).

The five quaternary neptunium compounds KCuNpS3, RbCuNpS3, CsCuNpS3, KAgNpS3, and CsAgNpS3 (AMNpS3) have been synthesized by the reaction of Np, Cu or Ag, S, and K2S or Rb2S3 or Cs2S3 at 793 K (Rb) or 873 K. These isostructural compounds crystallize as black rectangular plates in the KCuZrS3 structure type in space group Cmcm of the orthorhombic system. The structure comprises MS4 (M = Cu or Ag) tetrahedra and NpS6 octahedra that edge share to form ∞2[MNpS3−] layers. These layers are separated by the alkali-metal cations. The Np−S bond lengths vary from 2.681(2) to 2.754(1) A. When compared to the corresponding isostructural Th and U compounds these bond distances obey the expected actinide contraction. As the structure contains no S−S bonds, formal oxidation states of +1/+1/+4/−2 may be assigned to A/M/Np/S, respectively. From these results a value of 2.57 for the bond-valence parameter r0 for Np4+−S2− has been derived and applied to the estimation of the formal oxidation states of Np in the binary NpxSy...

Dark-red square plates of the previously reported compounds “(UO)2LnS3” (Ln = Yb, Y) have been synthesized by solid-state reactions of UOS and YbS or Y2S3 with Sb2S3 as a flux at 1273 K. The struct...

Red needles of UY{sub 4}O{sub 3}S{sub 5} have been synthesized by the solid-state reaction at 1273 K of UOS and Y{sub 2}S{sub 3} with Sb{sub 2}S{sub 3} as a flux. UY{sub 4}O{sub 3}S{sub 5} adopts a three-dimensional structure that contains five crystallographically unique heavy-atom positions. U and Y atoms disorder on one eight-coordinate metal position bonded to four O atoms and four S atoms and two seven-coordinate metal positions bonded to three O atoms and four S atoms. Another eight-coordinate metal position with two O and six S atoms and one six-coordinate metal position with six S atoms are exclusively occupied by Y atoms. UY{sub 4}O{sub 3}S{sub 5} is a modified Curie-Weiss paramagnet between 1.8 and 300 K. Its effective magnetic moment is estimated to be 3.3(2) mu{sub B}. UY{sub 4}O{sub 3}S{sub 5} has a band gap of 1.95 eV. The electrical resistivity along the [010] direction of a single crystal shows Arrhenius-type thermal activation with an activation energy of 0.2 eV. - Graphical abstract: View of the crystal structure of UY4O3S5.