Synthesizing Crystalline Chalcogenidoarsenates in Thiol-Amine Solvent Mixtures

Thiol-amine solvent mixtures have been widely applied in the solution processing of binary chalcogenide thin films due to their excellent ability to dissolve various bulk binary chalcogenides. However, application of this solvent system in preparing new crystalline chalcogenidometalates has not been explored. In this work, by using a thiol-amine solvent mixture of n-butylamine (BA) and 1,2-ethanedithiol (EDT) as the reaction medium and protonated piperazine (pip) cation as the template, we synthesized a series of new chalcogenidoarsenates with structures ranging from discrete clusters to two-dimensional layers, namely, [pipH₂][pipH][AsS₄] (1), [pipH₂][pipH][As(Se_0.4S_0.6)₄] (2), [pipH₂]₂[pipH]₂[In₂As^III₂As^V₂S_13.3(S₂)_0.7] (3), [pipH₂]₂[pipH]₂[In₂As^III₂As^V₂S_10.2Se_3.1(Se₂)_0.7] (4), [pipH₂]_0.5[AsS(S₂)] (5), [pipH₂]_0.5[AsS₂] (6), [pipH]₂[AgAsS₄] (7), [pipH₂]_1.5[GaAs^IIIAs^VS₇] (8), and Cs₂[pipH]₂[InAs₆S₁₂]Cl (9). Particularly, compounds 3, 4, and 8 contain mixed-valent As^III and As^V ions in their discrete clusters and one-dimensional chain. In addition, compound 5 could thermodynamically transform to compound 6 with increasing reaction temperature, which may be attributed to the thermodynamically unstable S-S species in the chains of 5. The BA-EDT solvent mixture was crucial to the synthesis of these compounds, since no title crystals can be prepared by replacing the BA-EDT solvent mixture with other conventional solvents or removing one component of the BA-EDT solvent mixture from the reaction system. Our research demonstrates that thiol-amine solvent systems could be promising reaction media for growing novel crystalline chalcogenidometalates.