title: Germanium selenophosphates: the incommensurately modulated 1/∞[Ge(4-x)P(x)Se12(4-)] and the molecular [Ge2P2Se14]6-.
abstract: The new germanium selenophosphates K(4)Ge(4-x)P(x)Se(12) (1) and Rb(6)Ge(2)P(2)Se(14) (2) are reported. The former is a one-dimensional metastable compound synthesized using the polychalcogenide flux method that crystallizes in the monoclinic space group P2(1)/c with lattice parameters a = 6.7388(7) Å, b = 13.489(1) Å, c = 6.3904(6) Å, and β = 91.025(8)°. At a glance, a mixed Ge(4+)/P(5+) tetrahedral site and disordered Se position are found among the corner sharing tetrahedra that make up the polymeric anion. After careful examination, the structure was found to be incommensurately modulated and a single q-vector of q = 0.4442(6)a* + 0.3407(6)c* was determined after annealing single crystals below their decomposition point for 30d. The latter compound contains the new discrete molecular anion [Ge(2)P(2)Se(14)](6-) and crystallizes in P1 with lattice parameters a = 7.2463(8) Å, b = 9.707(1)Å, c = 11.987(1)Å, α = 79.516(9)°, β = 89.524(9)°, and γ = 68.281(9)°. Both compounds are semiconductors with band gaps of 1 and 2 being 1.9 eV and 2.2 eV, respectively.
authors.affiliation: Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA.
authors.forename: Collin D
authors.initials: CD
authors.lastname: Morris
authors.forename: Christos D
authors.initials: CD
authors.lastname: Malliakas
authors.forename: Mercouri G
authors.initials: MG
authors.lastname: Kanatzidis