Complex cobalt silicates and germanates crystallizing in a porous three-dimensional framework structure

Four new cesium-containing cobalt oxide complexes were reported. Cs(Co0.5Si0.5)SiO4 (1), Cs1.29(5)Co0.69(5)Ge1.81(5)O5 (2), and its ordered analogue Cs2CoGe4O10 (3) were synthesized using a mixed CsCl–CsF flux at 850 °C or 900 °C. The structure of (1) closely resembles that of known zeolite and feldspar structures, and (1) crystallizes in the noncentrosymmetric monoclinic space group Im with lattice parameters of a = 8.9926(4) A, b = 5.4599(2) A, c = 9.3958(6) A, and β = 91.5928(18)°. Complexes (2) and (3) crystallize in the same new structure with a highly porous three-dimensional framework in the tetragonal space group I with lattice parameters of a = 7.4239(14) A and c = 13.169(3) A for (2) and a = 7.3540(6) A and c = 13.1122(11) A for (3). The formation of (2) vs. (3) can be controlled based on slight variations in the quantities of the starting materials. Single-crystal-to-single-crystal ion exchange of (1) in a molten RbNO3 bath resulted in 14% Cs exchange with Rb, affording the composition Cs0.86Rb0.14(Co0.5Si0.5)SiO4 (4). First-principles density functional theory calculations were performed to elucidate the electronic and magnetic properties and stabilities of (1) and (3) at 0 K.