Exploring the Surfactant–Thermal Synthesis of Crystalline Functional Thioarsenates

Dan-Dan Yang, Ying Song, Bo Zhang, Nan-Nan Shen, Gui-Lan Xu, Wei-Wei Xiong, Xiao-Ying Huang

Index: 10.1021/acs.cgd.8b00495

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Abstract

Two new crystalline thioarsenate compounds, formulated as [pipH2][Mn2As2S6] (1) and [TMDPH2][As4S6] (2) (pip = piperazine, TMDP = 1,3-bis(4-piperidyl)propane), have been surfactant–thermally synthesized with the utilization of octylamine and PEG-400 as the solvents. The crystal structure of 1 features [Mn2As2S6]n2n– anionic layers which are separated by doubly protonated [pipH2]2+ cations, while that of compound 2 is made of discrete [As4S6]2– clusters and doubly protonated [TMDPH2]2+ cations. Both compounds were characterized by powder X-ray diffraction analyses, solid-state optical diffuse reflectance spectroscopy, and thermogravimetric analyses. As estimated from the adsorption spectra, the band gaps of 1 and 2 are 2.32 and 2.49 eV, respectively. The electronic structure calculations based on density functional theory method confirm the indirect band gap of 2. In addition, the magnetic investigation of 1 suggests antiferromagnetic behavior. Since compound 2 crystallizes in the space group Imm2, the nonlinear optical property of 2 was studied, and its second harmonic generation intensity was nearly twice as much as that of KDP. Furthermore, compounds 1 and 2 exhibited a photocurrent response with the photocurrent intensities of 17.5 μA/cm2 and 2 μA/cm2, respectively.