Mild Hydro/Solvothermal Syntheses And Characterization Of Multinary Thiometalates

Chalcogenides is a kind of the most important functional inorganic materials. They possess complex architectures with potential applications due to the semiconductivity, selective ion exchange and electro-optical properties, and fast-ion conductivity. During the past few decades, a great number of binary and ternary chalcogenides have been synthesized under hydro/solvothermal conditions. The majority are based on main group metals. However, the very small solubility of transition metal chalcogenides often leads to a failure to incorporate of transition-metal ions into main group chalcogenides, therefore greatly limits the number of quaternary chalcogenides. In this dissertation, we advanced a new synthesis route by using excess S/S2-as mineralizer whereby a series of silver/copper-containing multinary sulfides have been obtained under mild hydro/solvothermal conditions. The syntheses, structures, thermal stabilities and semiconductor properties were investigated and discussed in detail.1. Five thioargentates Na5AgGe2S7(1), Rb2Ag2GeS4(2), Ag3MⅢS3(M=As, Sb)(3,4) and KAg2AsS3(5) were obtained in the presence of excess sulfur as mineralizer. Na5AgGe2S7(1) is a layered compound built from tetrahedral AgS4units and dimeric [Ge2Sy]6-moieties. It is the first2D sulfide in which the dimeric [Ge2S7]6-unit forms part of the bonding network. In the silver-rich compounds2-5, the self-condensation among main group chalcogenido-units is suppressed. Compound2consists edge-sharing tetrahedral AgS4chains which are further decorated by two chains formed by GeS4and AgS2units. In compounds3and4, monomeric [MS3](M=As, Sb) units link the [Ag2S2] chains into3D neutral framework. Compound5has a double-layered structure. And in each single layer, chains built from tetrahedral AgS4units and pyramidal AgS3units are connected by monomeric [ASS3] units.2. Three copper-thioantimonates(III)(enH2)o.5(Cu2SbS3)(6), Rb2Cu2Sb2S5(7) and Cs2Cu2Sb2S5(8) have been synthesized solvothermally. Compound6is previously reported by Bensch et al. By using alkali metal cations as structure-directing agents instead, two novel inorganic compounds7and8could be obtained. Compound7contains a [CuSbS3] net to which [Sb2S4] chains adhere through Cu-S bonds and Sb-Cu interactions to give a layered structure. In compound8, the layer is formed by edge-sharing tetrahedral CUS4chains linked by dimeric [Sb2S5] units. The results not only prove that excess S is an efficient mineralizer for CuT, but also reveal the strong structure-directing effect of alkali metal cations. We explored the solvothermal reaction system of A-Cu-As-S (A=alkali metal) in a similar way and obtained layered compounds K2CU2AS2S5(9) and Rb8Cu6As8Si(10). K2CU2AS2S5(9) is isomorphic with compound7. The layered structure of compound10is constructed by helical chains built from [CU3S7] moieties and dimeric [AS2S5] units which are further connected by tetrameric [AS4S9] groups.3. The structure-directing effect of alkali metal cations and tetramethylammonium ion was explored. Compound11could be obtained under mild conditions in the presence of excess sulfur as mineralizer, which possesses the a-NaFeO2structure type. By using [(Me)4N]+ions as structure-directing agents instead, compound [(Me)4N]6[In10S18](12) with large porosity could be obtained hydrothermally, which has a3D open framework built from T3clusters. The incorporation of Cu+leads to the formation of compound [(Me)4N]13[CusIn3oS54](13), which has a double-layered structure constructed by T5clusters. Our results indicate that tetramethylammonium is an efficient structure-directing agent for both ternary and quaternary indium sulfides. Moreover,[(Me)4N]+makes the hydrophobic polysulfides more soluble, so that the syntheses could be carried out in aqueous systems employing excess S2-anions as mineralizer.