Syntheses, structures, and electronic properties of Ba3FeUS6 and Ba3AgUS6.

The compounds Ba3FeUS6 and Ba3AgUS6 have been synthesized by the reactions of BaS, U, S, and M (= Fe or Ag) at 1223 K. These two isostructural compounds crystallize in the K4CdCl6 structure type in the trigonal system in space group D3d(6)­R3c. Both structures feature infinite ∞(1)[MUS6(6­)] chains along c that are separated by Ba atoms. The ∞(1)[FeUS6(6­)] chains are formed by the face-sharing of US6 trigonal prisms with FeS6 octahedra; in contrast, the ∞(1)[AgUS6(6­)] chains are formed by the face-sharing of US6 octahedra with AgS6 trigonal prisms. The Ba3FeUS6 compound charge balances with 3 Ba(2+), 1 Fe(2+), 1 U4+, and 6 S(2­), whereas Ba3AgUS6 charge balances with 3 Ba(2+), 1 Ag(1+), 1 U(5+), and 6 S(2­). This structure offers a remarkable flexibility in terms of the oxidation state of the incorporated uranium depending on the oxidation state of the d-block metal. DFT calculations performed with the HSE functional have led to band gaps of 2.3 and 2.2 eV for Ba3FeUS6 and Ba3AgUS6, respectively. From resistivity measurements, the Arrhenius activation energies are 0.12(1) and 0.43(1) eV for Ba3FeUS6 and Ba3AgUS6, respectively.

Synthesis, properties, and complex crystal structure of Th2Se5.

The compound Th(2)Se(5) has been synthesized and its structure determined by means of single-crystal X-ray diffraction methods. The subcell of Th(2)Se(5) is in the tetragonal space group P4(2)/nmc and is isostructural to Np(2)Se(5). The modulated structure of Th(2)Se(5) has been solved in the monoclinic super space group P2(α0γ)0. The structure features parallel infinite Se-Se chains with minimum and maximum Se-Se distances of 2.477(5) and 2.967(5) Å, respectively. Th(2)Se(5) is a semiconductor with an electrical resistivity that shows thermally activated Arrhenius behavior with an activation energy of 0.40(1) eV. From spectroscopic measurements, the band gap of Th(2)Se(5) is 0.37(2) eV. That the Th(2)Se(5) structure is modulated whereas the Np(2)Se(5) structure appears not to be implies that the formal oxidation state of Np in Np(2)Se(5) is 4+.

Syntheses and characterization of six quaternary uranium chalcogenides A2M4U6Q17 (A = Rb or Cs; M = Pd or Pt; Q = S or Se).

The A(2)M(4)U(6)Q(17) compounds Rb(2)Pd(4)U(6)S(17), Rb(2)Pd(4)U(6)Se(17), Rb(2)Pt(4)U(6)Se(17), Cs(2)Pd(4)U(6)S(17), Cs(2)Pd(4)U(6)Se(17), and Cs(2)Pt(4)U(6)Se(17) were synthesized by the high-temperature solid-state reactions of U, M, and Q in a flux of ACl or Rb(2)S(3). These isostructural compounds crystallize in a new structure type, with two formula units in the tetragonal space group P4/mnc. This structure consists of a network of square-planar MQ(4), monocapped trigonal-prismatic UQ(7), and square-antiprismatic UQ(8) polyhedra with A atoms in the voids. Rb(2)Pd(4)U(6)S(17) is a typical semiconductor, as deduced from electrical resistivity measurements. Magnetic susceptibility and specific heat measurements on single crystals of Rb(2)Pd(4)U(6)S(17) show a phase transition at 13 K, the result either of antiferromagnetic ordering or of a structural phase transition. Periodic spin-polarized band structure calculations were performed on Rb(2)Pd(4)U(6)S(17) with the use of the first principles DFT program VASP. Magnetic calculations included spin-orbit coupling. With U f-f correlations taken into account within the GGA+U formalism in calculating partial densities of states, the compound is predicted to be a narrow-band semiconductor with the smallest indirect and direct band gaps being 0.79 and 0.91 eV, respectively.

Thallium(I) copper(I) thorium(IV) tris-elenide, TlCuThSe(3).

Thallium(I) copper(I) thorium(IV) tris-elenide, TlCuThSe3, crystallizes with four formula units in the space group Cmcm in the KCuZrS3 structure type. There is one crystallographic-ally independent Th, Tl, and Cu atom at a site of symmetry 2/m.., m2m, and m2m, respectively. There are two crystallographically independent Se atoms at sites of symmetry m.. and m2m. The structure consists of sheets of edge-sharing ThSe6 octa-hedra and CuSe4 tetra-hedra stacked parallel to the (010) face, separated by layers filled with chains of Tl running parallel to [100]. Each Tl is coordinated by a trigonal prism of Se atoms.

Single-crystal structures, optical absorptions, and electronic distributions of thorium oxychalcogenides ThOQ (Q = S, Se, Te).

The compounds ThOS, ThOSe, and ThOTe have been synthesized, and their structures have been determined by means of single-crystal X-ray diffraction methods. All three compounds adopt the PbFCl structure type in the tetragonal space group D(4h)(7) - P4/nmm. More precise crystallographic data have been obtained for ThOS and ThOSe, which had previously only been known from X-ray powder diffraction data. ThOS, ThOSe, and ThOTe are yellow-, orange-, and black-colored, respectively. From single-crystal optical absorption measurements the band gaps are 2.22, 1.65, and 1.45 eV, respectively. Optical band gaps, ionic charges, and densities of states were calculated for the three compounds with the use of Density Functional methods.

Tetra-yttrium(III) tris-ulfide disilicate.

Tetra-yttrium(III) tris-ulfide disilicate, Y(4)S(3)(Si(2)O(7)), crystallizes in the Sm(4)S(3)(Si(2)O(7)) structure type. The structure consists of isolated (Si(2)O(7))(6-) units (2mm. symmetry) and two crystallo-graphically independent Y(3+) cations bridged by one S and one O atom. The first Y atom (site symmetry .m.) is coordinated by three O atoms and three S atoms in a trigonal-prismatic arrangement whereas the second Y atom (site symmetry ..2) is coordinated by six O atoms and three S atoms in a tricapped trigonal-prismatic arrangement.

Activity of nitrogen-containing and non-nitrogen-containing bisphosphonates on tumor cell lines.

We synthesized and tested three series of bisphosphonates for their activity in inhibiting the growth of three human tumor cell lines: MCF-7 (breast), NCI-H460 (lung), and SF-268 (CNS). The first series of compounds consisted of 49 nitrogen-containing bisphosphonates, the most active species being a tetrakispivaloyloxymethyl (POM) ester, having an (average) IC(50) of 6.8 microM. The second series of compounds consisted of nine terphenylbisphosphonates, the most active species also being a POM ester, having an IC(50) of 2.2 microM. The third series of compounds consisted of seven halogen or cyanophenylbisphosphonates, the most active species again being a POM ester, having an IC(50) of 500 nM. Taken together, these results are of interest because they show that bisphosphonate esters can have potent activity against a variety of tumor cell lines, with the most active terphenyl- and halophenyl-containing species having IC(50) values approximately 10-40x lower than the most potent commercially available bisphosphonates.