Hydrothermal synthesis of [C6H16N2][In2Se3(Se2)]: A new one-dimensional indium selenide

A new organically templated indium selenide, C₆H₁₆N₂]In₂Se₃(Se₂)], has been prepared hydrothermally from the reaction of indium, selenium and trans-1,4-diaminocyclohexane in water at 170 °C. This material was characterised by single-crystal and powder X-ray diffraction, thermogravimetric analysis, UV-vis diffuse reflectance spectroscopy, FT-IR and elemental analysis. The compound crystallises in the monoclinic space group C2/c (a=12.0221(16) Å, b=11.2498(15) Å, c=12.8470(17) Å, β=110.514(6)°). The crystal structure of C₆H₁₆N₂]In₂Se₃(Se₂)] contains anionic chains of stoichiometry In₂Se₃(Se₂)]²⁻, which are aligned parallel to the 1 0 1] direction, and separated by diprotonated trans-1,4-diaminocyclohexane cations. The In₂Se₃(Se₂)]²⁻ chains, which consist of alternating four-membered In₂Se₂] and five-membered In₂Se₃] rings, contain perselenide (Se₂)²⁻ units. UV-vis diffuse reflectance spectroscopy indicates that C₆H₁₆N₂]In₂Se₃(Se₂)] has a band gap of 2.23(1) eV.