Germanium selenophosphates: The incommensurately modulated ¹/_∞[Ge_4-xP_xSe ₁₂^4-] and the molecular [Ge₂P ₂Se₁₄]^6-

The new germanium selenophosphates K₄Ge_4-xP _xSe₁₂ (1) and Rb₆Ge₂P ₂Se₁₄ (2) are reported. The former is a one-dimensional metastable compound synthesized using the polychalcogenide flux method that crystallizes in the monoclinic space group P2₁/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 Ge⁴⁺/P⁵⁺ 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 [Ge₂P₂Se ₁₄]^6- and crystallizes in P1̄ 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.