Bi2S3 Bipyramids in Layered Sulfides M2Bi2S3(AlCl4)2 (M=Ag, Cu)

摘要: Black Cu2Bi2S3(AlCl4)2 and orange Ag2Bi2S3(AlCl4)2 were synthesized by solvent-free reaction (polycrystalline powders) as well in Lewis-acidic ionic liquids (crystals) at temperatures of 200 °C or lower. X-ray diffraction on single-crystals revealed two centrosymmetric polytypes: a rhombohedral one, space group Rc [a = 658.02(3) pm, c 6794.3(3) pm], with six formula units the unit cell (6R polytype), hexagonal P63/m 658.71(6) 2265.5(3) (2H polytype). is homeotypic crystallizes acentric P2c 691.65(3) 2207.86(9) per (2H′ All structures consist 2∞[(M+)2Bi2S3] layers (M Cu, Ag) separated double AlCl4– tetrahedra differ mainly their stacking sequences orientation groups. The sulfidometalate layer honeycomb-like network M+ S2– ions plane, whereas pairs Bi3+ cations occupy positions above below plane. analysis chemical bonding reveals strong covalent two-center two-electron bonds five-atomic bipyramidal Bi2S3 (D3h symmetry) much higher component to coin metal cations. DFT-optimized shape an isolated hypothetical molecule differs only marginally from that layer. Hence, compounds might be interpreted molecules embedded MAlCl4 salts. Optical bandgaps 1.6 eV Cu) 2.2 deduced diffuse reflectance measurements. DFT-based quantum calculations indicate direct same magnitude.