Cs8M4(P2Se6)5 (M = Sb, Bi) were synthesized by reacting Bi (Sb) with a molten mixture of Cs2Se/P4Se10/Se at 460°C. The structure features weak M⋯M interactions and a [P2Se6]4- ligand in three unique bonding modes. The [M4(P2Se6)5]n 8n- layers are composed of [M4(P2-Se6)4] zigzag chains that are linked via [P2Se6]4- ligands to form a staircase layered framework. The layers are interdigitated to form tunnels along the b direction. Cs+ ions are found in the tunnels and within the layers. The dark red crystals of Cs8Sb4(P2Se6)5 (I) (75% yield) and the black crystals of the isostructural Cs8Bi4(P2Se6)5 (II) (90% yield) are stable in air and water. Compound I crystallizes in the monoclinic space group P21/n (No. 14) with a = 15.489(3) Å, b = 11.505(2) Å, c = 17.772(3) Å, β = 95.59(2)°, V = 3152 Å3, Z = 2, and dc = 4.455g/cm3, with Fo2 > 3σ(Fσ2)=3544, number of variables = 236, and 2θmax = 50°. The final R/Rw = 3.2/4.9. Compound II is X-ray isomorphous with a = 15.752(4) Å, b = 11.523(2) Å, c = 17.916(2) Å, β = 95.20(2)°, V = 3241 Å3, Z = 2, and dc=4.694 g/cm3, with Fo2 > 3σ(Fσ2) = 2598, number of variables = 236, and 2θmax = 50°. The final R/Rw = 5.4/6.7. The optical band gaps of I and II were determined by optical spectroscopy to be 1.58 and 1.44 eV, respectively. Both compounds melt congruently at 532 (I) and 497°C (II).
|Number of pages||8|
|Journal||Chemistry of Materials|
|Publication status||Published - 1994|
ASJC Scopus subject areas
- Materials Chemistry
- Materials Science(all)