Ionothermal Synthesis of Two New Thioantimonates with Transition Metal Regulation

Under the regulation of transition metal Ag+, two new metal chalcogenides Rb2Sb4S7 and RbAgSb4S7·H2O have been prepared by ionothermal method under mild temperature. The crystal structure of Rb2Sb4S7 possesses two kind of metal centers [SbS3]3− triangular pyramid and [SbS4]5− twisted tetrahedron, and form a one-dimensional (1-D) cluster chain with free alkali metal cations. RbAgSb4S7·H2O possesses [SbS3]3− triangular pyramid, [SbS4]5− and [AgS4]7− twisted tetrahedrons, and exhibits a unique three-dimensional (3-D) framework with six kinds of member rings (MR), free alkali metal cations and free H2O molecules. Especially, 20-MR is first found in thioantimonates. The band gaps of Rb2Sb4S7 and RbAgSb4S7·H2O are 1.73 and 1.85 eV, respectively, which indicates that these two compounds can act as semiconductor materials. And the birefringences of Rb2Sb4S7 and RbAgSb4S7·H2O are calculated to be 0.182 and 0.065 at 1064 nm, respectively. Under the same synthesis condition, the addition of transition metal Ag+ has a great influence on their crystal structures and band gaps, which provides the possibility for designing and synthesizing diversified chalcogenides under ionothermal conditions.