Aluminosilicate Relatives: Chalcogenoaluminogermanates Rb₃(AlQ₂)₃(GeQ₂)₇ (Q = S, Se)

The new compounds Rb₃(AlQ₂)₃(GeQ₂)₇ [Q = S (1), Se (2)] feature the 3D anionic open framework [(AlQ₂)₃(GeQ₂)₇]³⁻ in which aluminum and germanium share tetrahedral coordination sites. Rb ions are located in channels formed by the connection of 8, 10, and 16 (Ge/Al)S₄ tetrahedra. The isostructural sulfur and selenium derivatives crystallize in the space group P2₁/c. 1: a = 6.7537(3) Å, b = 37.7825(19) Å, c = 6.7515(3) Å, and β = 90.655(4)°. 2: a = 7.0580(5) Å, b = 39.419(2) Å, c = 7.0412(4) Å, β = 90.360(5)°, and Z = 2 at 190(2) K. The band gaps of the congruently melting chalcogenogermanates are 3.1 eV (1) and 2.4 eV (2).