Abstract
The new compounds Rb-3(AlQ(2))(3)(GeQ(2))(7) [Q = S (1), Se (2)] feature the 3D anionic open framework [(AlQ(2))(3)(GeQ(2))(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)S-4 tetrahedra. The isostructural sulfur and selenium derivatives crystallize in the space group P2(1)/c. 1: a = 6.7537(3) angstrom, b = 37.7825(19) angstrom, c = 6.7515(3) angstrom, and beta = 90.655(4)degrees. 2: a = 7.0580(5) angstrom, b= 39.419(2) angstrom, c= 7.0412(4) angstrom, beta = 90.360(5)degrees, 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).