Sara Reiser

Refinement of the crystal structures of Cu₃PS₄ and Cu₃SbS₄ and a comment on normal tetrahedral structures

Abstract The crystal structures of yellow Cu3PS4 and of black Cu3SbS4 were refined from single crystal X-ray diffraction data. Cu3PS4 crystallizes orthorhombic in an ordered wurtzite superstructure type with the space group Pmn21 (no. 31), a = 7.282(1) Å, b = 6.339(1) Å, c = 6.075(1) Å, V = 280.38(8) Å3, and Z = 2. The refinement converged to R = 0.0276, and wR2 = 0.0710 for 737 unique reflections and 44 parameters. Cu3SbS4 crystallizes tetragonal in an ordered sphalerite superstructure type with the space group I4̅2m (no. 121), a = 5.391(1) Å, c = 10.764(1) Å, V = 312.83(9) Å3, and Z = 2. The refinement converged to R = 0.0213, and wR2 = 0.0532 for 492 unique reflections and 14 parameters. The crystal structures of the title compounds and related normal tetrahedral structures are discussed with respect to the preference of either hexagonal or cubic packing of the anions.

(CuI)3P4S4: Preparation, Structural, and NMR Spectroscopic Characterization of a Copper(I) Halide Adduct with β-P4S4

(CuI)(3)P(4)S(4) is obtained by reaction of stoichiometric amounts of CuI, P, and S in evacuated silica ampoules. The yellow compound consists of monomeric beta-P(4)S(4) cage molecules that are separated by hexagonal columns of CuI. (CuI)(3)P(4)S(4) crystallizes isotypic to (CuI)(3)P(4)Se(4) in the hexagonal system, space group P6(3)cm (no. 185) with a=19.082(3), c=6.691(1) A, V=2109.9(6) A(3), and Z=6. Three of the four phosphorus atoms are bonded to copper, whereas no bonds between copper and sulfur are observed. The two crystallographically distinct copper sites are clearly differentiated by (65)Cu magic-angle spinning (MAS) NMR spectroscopy. Furthermore, an unequivocal assignment of the (31)P MAS-NMR spectra is possible on the basis of homo- and heteronuclear dipole-dipole and scalar interactions. Dipolar coupling to the adjacent quadrupolar spins (63, 65)Cu generates a clear multiplet structure of the peaks attributable to P1 and P2, respectively. Furthermore, the utility of a newly developed two-dimensional NMR technique is illustrated to reveal direct connectivity between P atoms based on ((31)P-(31)P) scalar interactions.

NMR studies of phosphorus chalcogenide–copper iodide coordination compounds

The local structures of the new phosphorus chalcogenide – copper iodide coordination compounds (CuI)P4Se4, (CuI)2P8Se3, (CuI)3P4Se4, and (CuI)3P4S4 are investigated using comprehensive 63Cu, 65Cu, and 31P magic angle spinning NMR techniques. Peak assignments are proposed on the basis of homo- and heteronuclear indirect spin–spin interactions, available from lineshape analysis and/or two-dimensional correlation spectroscopy. In particular, the 31P-63,65Cu scalar coupling constants have been extracted from detailed lineshape simulations of the 31P resonances associated with the Cu-bonded P atoms. In addition, the RNνn pulse symmetry concept of Levitt and coworkers has been utilized for total through-bond correlation spectroscopy (TOBSY) of directly-bonded phosphorus species. The resonance assignments obtained facilitate a discussion of the 31P and 63,65Cu NMR Hamiltonian parameters in terms of the detailed local atomic environments. Analysis of the limited data set available for this group of closely related compounds offers the following conclusions: (1) bonding of a special phosphorus site in a given P4Xn (X = S, Se) molecule to Cu+ ions shifts the corresponding 31P NMR signal upfield by about 50 ppm relative to the uncomplexed molecule, (2) the magnitude of the corresponding scalar 31P-63,65Cu spin–spin coupling constant tends to decrease with increasing Cu–P distance, and (3) the 63,65Cu nuclear electric quadrupolar coupling constants appear to be weakly correlated with the shear strain parameter specifying the degree of local distortion present in the four-coordinated [CuI2P2] and [CuI3P] environments. Overall, the results illustrate the power and potential of advanced solid state NMR methodology to provide useful structural information in this class of materials.

Preparation, structural, Raman and impedance spectroscopic characterisation of the silver ion conductor (AgI)2Ag3SbS3

Pale yellow (AgI)2Ag3SbS3 was synthesized by the reaction of stoichiometric amounts of AgI and Ag3SbS3 (2 ∶ 1) at 683 K. It is air stable for several months. The crystal structure was determined at different temperatures in the range from 173 K to 573 K by single crystal X-ray diffraction. (AgI)2Ag3SbS3 crystallizes in the orthorhombic system, space group Pnnm (no. 58) with a = 10.9674(8) A, b = 13.5200(12) A, c = 7.7460(5) A, V = 1156.3(5) A3, and Z = 4 (data at 298 K). The title compound is isotypic with (CuI)2Cu3SbS3, at least for the positions of I, Sb, and S. The silver atoms are highly disordered and therefore their displacement parameters were refined using a Gram–Charlier non-harmonic development. No phase transition is observed between 173 K and the melting point at 720 K (DSC, onset temperature). The distribution of silver changes drastically with temperature and the localization of silver increases at low temperature. A high ionic conductivity is observed in combination with a pronounced disorder of the silver atoms. Impedance spectroscopic measurements reveal specific conductivity data of σ = 8.15 × 10−5 Ω−1 cm−1 at 332 K and of σ = 1.52 × 10−3 Ω−1 cm−1 at 478 K. The activation energy is EA = 0.29 eV. Raman spectra are dominated by the stretching modes of the [SbS3]3− units at 357, 327 and 316 cm−1 at room temperature.